CHAPTER PREVIEW
In this chapter we will begin our journey into the world of neuroscience. We will define important terms, like neurology, to help us begin to frame this world. We will then make a case on why it is important for a speech-language pathologist and audiologist to have a working knowledge of the nervous system. Lastly, we will examine theoretical perspectives and technologies that speak to the question: How does the brain work?
CHAPTER OUTLINE
IN THIS CHAPTER
In this chapter, we will . . .
■ Define the term neurology
■ Discuss why speech-language pathologists and audiologists need to know and understand neurology
■ Discuss why the neurological system is a precious resource
■ Answer the question: What does neurology mean to me?
■ Define the terms function, activity, and participation barriers
■ Survey examples of famous people who have suffered neurological conditions
■ Examine statistics concerning neurological disorders
■ List various categories of neurological disorders
■ Discuss basic theoretical perspectives as to how the brain works
■ Survey important researchers in the history of neuroscience
■ Compare and contrast neuroimaging techniques
■ Discuss why these theoretical perspectives matter to fields associated with communication sciences and disorders
■ Introduction: Defining Neurology
■ The Need for Neurological Training
■ A Broad Overview of the Nervous
System
• The Nervous System Is a Precious Resource
• What Does Neurology Mean to Me?
• Famous People With Neurological Conditions
• Prevalence, Incidence, and Cost of Neurological Disorders
• Classification of Neurological Disorders
■ A Brief History of Neuroscience
• Prehistory
• Early History
• Later History
• Modern History
■ Neuroscience Today
• Structural Imaging Techniques
• Functional Imaging Techniques
• Combined Structural and Functional Imaging Techniques
• Which Test When?
• A Caution Regarding Imaging Techniques
■ Conclusion
■ Summary of Learning Objectives
■ Key Terms
■ Draw It to Know It
■ Questions for Deeper Reflection
■ Case Study
■ Suggested Projects
■ References
LEARNING OBJECTIVES
1. The learner will define the following terms: neurology, anatomy, physiology, and pathology.
2. The learner will be able to create an argument as to why speech-language pathologists and audiologists need neurological training.
3. The learner will be able to list various categories of neurological disorders and provide one example in each category.
4. The learner will be able to draw and explain the spectrum of belief as to how the brain works.
5. The learner will list and define structural and functional imaging techniques and list at least one reason why communication disorders professionals should know about neuroimaging techniques.
► Introduction: Defining Neurology
We begin our journey into the human nervous system with this question from the anthropologist Stephen Juan: “Have you ever wondered about how fantastic the human brain really is? Every thought, every action, every deed relies upon this incredible organ. Although we take the brain for granted, we couldn’t wonder without it” (Juan, 1998, p. 1). The brain is the vehicle we use to wonder. It includes not only the brain but also those other parts of the neurological system that pertain to communication. Neurology is simply the study of the anatomy, physiology, and pathology of the nervous system. Anatomy is the study of structure, physiology is the study of function or structures in motion, and pathology is the study of disease processes that affect both anatomy and physiology. Put the prefix neuro- in front of each of these words and you get distinct yet highly related fields of study. Neuroanatomy is the study of the nervous system’s structure. A neuroana- tomical topic is a neuron (i.e., a nervous system cell) and its structure. When we want to talk about how a neuron functions, we have just entered into the area of neurophysiology. The study of nervous system diseases is called neuropathology. An example of neuropathology would be amyotrophic lateral sclerosis, or Lou Gehrig disease, which affects both the anatomy and physiology of neurons and leads to serious neurological problems. There are other fields in addition to these, including neurosurgery (removal of structures that impair normal nervous system functioning), neuroradiology (use of radiation therapy for nervous system tumors), and neuroembryology (normal and pathological development of the nervous system).
The nervous system is a series of organs that make communication between the brain and body possible in order for us to interact with the world around us. It is through the nervous system’s connections to the body (and vice versa) that we think, feel, and act. The most well-known organ of the nervous system is the brain, followed by the spinal cord and then the various nerves (FIGURE 1-1). The purpose of this chapter is to give a broad overview of the nervous system as well as a brief survey of neuroscience’s history and the important figures in that history. This chapter also explores modern neuroimaging techniques that have led to a better understanding of the brain and how it works.
FIGURE 1-1 The brain, spinal cord, and nerves are the major components of the human nervous system.
► The Need for Neurological Training
Why should a speech-language pathologist (SLP) or audiologist be concerned about the anatomy, physiology pathology of the nervous system? What difference does this knowledge make to clinical practice?
Rubens (1977), a neurologist, outlined several reasons why SLPs and audiologists should know about neuroscience and neurology. First, he argued that these professionals should know how to speak the language of neurology so that they and neurologists could better communicate. Neurologists have their own language. When communication disorders professionals have knowledge of this language, they can communicate more easily with neurologists. In turn, neurologists may be more willing to learn the language of SLPs and audiologists. An example of this neurological language is the word dyskinesia, a general word for a disorder of movement. Neurologists also extensively use abbreviations (e.g., CVA for cerebral vascular accident, or stroke) and use them considerably in their charting. Knowing these terms and abbreviations can obviously help the SLP or audiologist understand the neurologist’s assessment report and progress notes. Second, knowing about the nervous system and where a lesion is (e.g., frontal lobe versus occipital lobe) helps the SLP anticipate likely patient problems and choose appropriate initial testing instruments. For example, a patient with a focal left hemisphere stroke will be tested differently than someone with diffuse brain injury due to a traumatic brain injury. Third, knowing about neurological etiologies, such as stroke, traumatic brain injury, and brain tumor, helps an SLP or audiologist predict the kinds of problems patients are likely to face. For example, a patient with occlusion of the middle cerebral artery will have a different symptom complex (e.g., speech and language) than will a patient with posterior cerebral artery occlusion (e.g., visuospatial). Fourth, a working knowledge of neuroscience helps SLPs and audiologists document patient change and determine the efficacy of various treatment methods in rewiring the brain for improved communication. Fifth and connected to the previous point, knowledge of neural plasticity (i.e., the brain’s ability to change and adapt after injury) helps the SLP plan therapy in a way that takes advantage of this phenomenon. One principle of neuroplasticity is that repetition matters, meaning repeated experience can help the brain learn new skills. This insight can obviously be used in therapy by giving numerous repetitions of certain sounds or words, thus improving a patient’s likelihood of learning and generalizing these new skills.
SLPs and audiologists must do their part in fostering good relationships with neurologists and other doctors; one important way of gaining their colleagues’ respect is by being excellent at what they do. Nothing elicits respect like a job well done. Though SLPs and audiologists are autonomous professionals (i.e., they are not supervised by neurologists or other doctors), they depend on neurologists for many things, such as referrals and important neurological information on the patient (LaPointe, 1977). Tending to their relationships with these physicians not only helps SLPs and audiologists in these areas, but also ultimately helps patients receive the important and specialized services that only SLPs and audiologists can provide. I often tell my students that no one— not even neurologists—will know more about speech, language, hearing, or swallowing than they will once they are through graduate school and their clinical fellowship. This is not said out of pride, but rather out of reality; no one has as much clinical training in these areas as a licensed, certified SLP or audiologist, just like no one has as much knowledge of neurology as a neurologist.
Some readers might be thinking, “Well, that’s all fine, but I’m not going to work in a hospital or with neurologists. I’m going to work in a public school. What does all this matter to me?” Manasco (2017) offers a helpful maxim: “When you hear hoof beats, think horses, not zebras” (p. 5). What this adage is saying is that horses are the most likely explanation, while zebras are the outliers, the unexpected possibilities. Imagine you are working in a public school and a child walks into your office. Most likely, the child was sent to your office because he or she has a developmental language or speech sound disorder (i.e., a horse). However, it is possible the child was referred for testing because he or she has had a severe concussion or a stroke (i.e., a zebra). At some point, a child will walk into your office and your knowledge of neurology and neurogenic communication disorders will be needed to properly assess, diagnose, and treat that child. As Manasco explains, “You must be able to recognize and treat those problems in your field that are very out of the ordinary or even extraordinary” (2017, p. 5).
► A Broad Overview of the Nervous System
The Nervous System Is a Precious Resource
I remember watching the 2008 Summer Olympic Games on television with my 4-year-old daughters and seeing their joy and amazement as gymnasts Nastia Liukin and Shawn Johnson moved with grace and precision on the vault, floor exercises, uneven bars, and balance beam (FIGURE 1-2). Nastia took the gold in the individual all-around and Shawn the silver. It was a proud moment for the U.S. Olympic squad and all Americans watching these amazingly skilled athletes contort their bodies in incredible ways. The precision, timing, and coordination of these athletes had come from years of training not only their muscles but also their nervous systems. Plans for motor (or movement) activity were developed through years of repetitive action. As the adage goes, “Practice makes perfect.”
The nervous system is on full display in the works of our favorite composers and performers. They have fine-tuned their nervous systems through hours of practice to execute precisely the actions needed to perform a piece of music or create a piece of art. Itzhak Perlman (FIGURE 1-3), the famous violinist, began playing the violin at 3 years old and, although he contracted polio at an early age, practiced for numerous hours and became one of the world’s most famous violinists. Great feats of the body are in part products of the nervous system. The nervous system is definitely a precious resource, one that works quietly in the background, unknown by us unless a disease develops.
FIGURE 1-2 A gymnast on a balance beam illustrating how years of practice hone the nervous system.
Courtesy of Bill Evans/U.S. Air Force.
FIGURE 1-3 Itzhak Perlman playing at the White House for President George W. Bush and First Lady Laura Bush.
Courtesy of Shealah Craighead/George W. Bush Presidential Library and Museum.
What Does Neurology Mean to Me?
The nervous system is like an automatic transmission in a car; one does not need to think about shifting the gears. The nervous system comes into the forefront when something goes wrong with it. A neurological disorder involves a disease in the nervous system that impairs a person’s health, resulting in some level of disability. The World Health Organization’s (WHO’s) International Classification of Functioning, Disability and Health (ICF) defines disability as “a universal human experience, sometimes permanent, sometimes transient” that affects the health and functioning of a person (WHO, 2014). We should not think of people in two categories (healthy versus disabled), but rather remember that we are all on a spectrum with health at one end and disability at the other end. There are times in our lives when we experience more health and less disability, and vice versa.
Earlier generations used the terms impairment, disability, and/or handicap when discussing people who had health issues, and these terms are still widely used in everyday language (e.g., think of how most people refer to parking spaces with a wheelchair sign). WHO has attempted to change this language by using the alternative terms function, activity, and participation. The older terms of impairment, disability, and handicap come from the medical model of disability that puts an emphasis on the person’s health condition, his or her limitations due to this condition, and cures or treatment. The medical model does not include the role of society in disability and the barriers a society can erect for those with disabilities (i.e., the social model of disability). The focus of the medical model is on biological and medical answers. WHO’s use of alternative terms is an attempt to blend the social model of disability, which emphasizes the role of society and its barriers, with the medical model. WHO’s model still has elements of the medical model by stressing a person’s health condition (e.g., stroke) and how that condition has affected the structure and function of the body (e.g., paralysis). Issues with function barriers (formerly impairment) “are problems in body function or alterations in body structure” (WHO, 2011, p. 5). Examples of function issues include paralysis and blindness. In the area of communication disorders, examples include hearing loss and language impairment. Activity barriers (formerly disability) “are difficulties in executing activities” (WHO, 2011, p. 5), especially skills of daily living like walking or eating. For example, neurogenic communication disorders can lead to issues in the daily communication of needs and wants with other people or eating. Lastly, participation barriers (formerly handicap) “are problems with involvement in any area of life” (WHO, 2011, p. 5). These barriers include challenges participating in education and employment, often due to external barriers such as discrimination and transportation problems. It is important to note that not everyone who has a function barrier will have barriers in activity and/ or participation. For example, a person who is deaf may technically have hearing dysfunction but have no issues with daily activities or involvement in other areas of life.
FIGURE 1-4 The interaction between functioning, disability, and health.
WHO’s ICF also “looks beyond the idea of a purely medical or biological conceptualization of dysfunction, taking into account the other critical aspects of disability” (WHO, 2014), such as environmental and personal factors (FIGURE 1-4). Environmental factors describe the world in which people with neurological disorders live and interact. These factors can act as either facilitators or barriers and include products, technology, buildings, support, relationships, attitudes, services, systems, and policies. Personal factors relate directly to the person with a neurological disorder. For example, a person’s motivation and self-esteem can play into his or her interaction with the environment (WHO, 2011). FIGURE 1-5 illustrates WHO’s ICF applied to someone who has suffered a spinal cord injury.
It is likely that you have an acquaintance, friend, or family member who suffers from some sort of nervous system problem, such as Alzheimer or Parkinson disease, which may disable or handicap the person. If so, then neurology has personal significance to you. In other words, neurology is not a study that is distant from us; it affects our personal lives, especially when our loved ones or we ourselves experience a neurological disorder.
Famous People With Neurological Conditions
Neurological disorders do not discriminate. They strike the old and the young, the rich and the poor, and people of every color, culture, and nationality.
FIGURE 1-5 An example of the ICF applied to a case involving spinal cord injury.
Adapted from the Centers for Disease Control and Prevention. (n.d.). The ICF: An overview. Retrieved from https://www.cdc.gov /nchs/data/icd/icfoverview_finalforwho10sept.pdf
Many famous people have suffered from serious neurological conditions. Former president Ronald Reagan died from complications related to Alzheimer disease, a progressive neurological disorder that results in intellectual decline. Actor Michael J. Fox has Parkinson disease, a degenerative disorder of the central nervous system characterized by muscle rigidity and tremors. Actor Christopher Reeve suffered spinal cord injury in his upper neck after being thrown from a horse and was wheelchair bound and ventilator dependent until his death in 2004 from cardiac arrest. Stephen Hawking, the famous English physicist, was diagnosed at 21 years of age with an unusual form of amyotrophic lateral sclerosis (ALS; also known as Lou Gehrig disease); he struggled with this disease until his death in 2018 at 76 years old. Roy Horn, an entertainer from the famous Las Vegas tiger act known as Siegfried and Roy, suffered a stroke after his tiger Montecore bit him in the neck. Roy had fallen during a performance, and it is thought that Montecore was trying to pull him to safety. Most people suffer from neurological conditions privately, but these celebrities have had to endure their conditions in the public eye. 'Iheir willingness to share openly about their conditions has led to greater public awareness regarding conditions like ALS and Parkinson disease.
FIGURE 1-6 An illustration of important epidemiological terms.
Prevalence, Incidence, and Cost of Neurological Disorders
Statistics regarding the incidence (i.e., the number of new cases per year in a given population) and prevalence (i.e., the total number of current cases in a given population at a point in time) of neurological disorders are challenging to obtain due to the relatively few available studies (FIGURE 1-6 illustrates these important epidemiological terms). One study by Hirtz et al. (2007), summarized in FIGURE 1-7, estimated the incidence and prevalence of select neurological disorders in the United States. Because population statistics change rapidly, Hirtz et al.’s information is out of date for some conditions; for example, the Centers for Disease Control and Prevention (2018) and Baio et al. (2018) report that the prevalence rate for children with autism spectrum disorder is now 16.8/1,000, or 1 in 59 children.
Whatever the statistics, the number of people suffering from neurological disorders is great. In fact, WHO estimates that nearly one in six people worldwide, or about 1 billion people, suffer from a neurological disease (Bertolote, 2007).
In addition to the personal hardships of people affected, there is also a tremendous financial cost associated with the assessment and treatment of neurological disorders. Gooch, Pracht, and Borenstein (2017) report that the following disorders alone cost the United States approximately $800 billion per year: Alzheimer disease and other dementias, stroke, traumatic brain injury, chronic lower back pain, migraine, epilepsy, multiple sclerosis, spinal cord injury, and Parkinson disease (FIGURE1-8). The treatment of Alzheimer disease led the list with an annual cost of approximately $243 billion.
FIGURE 1-7A A. Incidence of select neurological disorders in the United States (new cases per 100,000).
FIGURE 1-7B B. Prevalence of select neurological disorders in the United States (total cases per 1,000). ALS = amyotrophic lateral sclerosis.
Data from: Hirtz, D., Thurman, D. J., Gwinn-Hardy, K., Mohamed, M., Chaudhuri, A. R., & Zalutsky, R. (2007). How common are the "common” neurologic disorders? Neurology, 68, 332.
FIGURE 1-8 Annual cost of major neurological disorders in billions of dollars. AD = Alzheimer disease, MS = multiple sclerosis, SCI = spinal cord injury, TBI = traumatic brain injury.
Data from: Gooch, C. L., Pracht, E., & Borenstein, A. R. (2017). The burden of neurological disease in the United States: A summary report and call to action. Annals of Neurology, 81(4), 479-484.
Classification of Neurological Disorders
WHO has developed a classification system for diseases, including pathologies of the nervous system, called the International Statistical Classification of Diseases and Related Health Problems. This name is commonly shortened to the International Classification of Diseases and, because it is in its 10th edition, is abbreviated ICD-10. Under “Diseases of the Nervous System,” there are 11 subcategories of neurological diseases (WHO, 2010). These categories are briefly described here:
Inflammatory diseases: These are neurological diseases caused by bacterial, viral, or parasitic pathogens. Two conditions under this category are encephalitis (brain infection) and meningitis (infection of membranes that surround the brain and spinal cord).
Systematic atrophies primarily affecting the central nervous system: Atrophy refers to a wasting away of something, in this case the nervous system. The progressive, hereditary disorder known as Huntington disease is an example of a condition in this category.
Extrapyramidal and movement disorders: The extra- pyramidal system is that part of the nervous system that regulates our movements. The basal ganglia serve as a kind of control center for this system. Parkinson disease, a degenerative neurological disease involving rhythmic shaking, is an example.
Other degenerative diseases of the nervous system: Other conditions that are degenerative in nature, but do not involve the extrapyramidal system, are included in this category. An example is Alzheimer disease, which is a progressive neurological disorder involving gradual loss of cognitive abilities.
Demyelinating diseases of the central nervous system: Myelin is a white, fatty substance that insulates our nerve tracts; thus, demyelinating diseases like multiple sclerosis involve the stripping of myelin from the nerve tracts. This process leads to muscle weakness.
Episodic and paroxysmal disorders: This classification involves disorders that come and go instead of being chronic. They can also be characterized by sudden or paroxysmal attacks. Epilepsy, headaches, stroke, and sleep disorders make up the four general conditions found under this category.
Nerve, nerve root, and plexus disorders: These conditions involve nerves, nerve roots, and branching networks of nerves. One example is Bell palsy, which is a condition that affects the facial nerve and causes paralysis to one side of the face. Another example is phantom limb syndrome, in which amputees continue to have sensation from their absent limb.
Polyneuropathies and other disorders of the peripheral nervous system: The central nervous system involves the brain and spinal cord, and the peripheral nervous system involves all the nerves that connect the central nervous system with body structures, such as muscles, sense organs, and glands. Guillain-Barre syndrome is an acute polyneuropathy affecting the peripheral nervous system. It is life threatening due to the profound weakness that occurs, especially to the respiratory muscles.
Diseases of the myoneural junction and muscle: These disorders result from problems where a nerve and muscle connect, called the myoneural or neuromuscular junction. Myasthenia gravis is a condition whose name means grave muscle weakness. It is an autoimmune disorder in which the body attacks the neuromuscular junction, inhibiting an important chemical needed to make muscles contract.
Cerebral palsy and other paralytic conditions: Most people have heard of cerebral palsy, which occurs due to brain injury before or at birth and leads to difficulties in muscle tone and posture. These problems lead to struggles in completing activities and interacting with the environment. Spinal cord injury and the resulting weakness or paralysis is included in this category.
Other disorders of the nervous system: WHO has included this category to catch any pathology that does not fit in any of the previous categories. For example, episodes of oxygen deprivation, called anoxic events, are classified here. Another example is hydrocephalus, in which the brain ventricles swell and compress the brain tissues against the skull.
The ICF, mentioned earlier, is complementary to the ICD-10. It lays out a broad framework of health, whereas the ICD-10 focuses on disease. The ICF includes the following general categories: body functions, body structures, activities, participation, and environmental factors. There are several subcategories that are relevant to the SLP and audiologist; these are described in BOX 1-1. Readers can explore these subcategories in more detail by visiting the ICF website (www.who.int/classifications/icf/en/).
BOX 1-1 International Classification of Functioning, Disability and Health Related to Communication
|
Body Functions |
Body Structures |
|
|
■ Chapter 2: Sensory Functions and Pain • b210-b229 Seeing and related functions • b230-b249 Hearing and vestibular functions ■ Chapter 3: Voice and Speech Functions • b310 Voice functions • b320 Articulation functions • b330 Fluency and rhythm of speech functions • b340 Alternative vocalization functions • b398 Voice and speech functions, other specified • b399 Voice and speech functions, unspecified |
■ Chapter 1: Structures of the Nervous System • s110 Structure of brain • s120 Spinal cord and related structures • s130 Structure of meninges • s140 Structure of sympathetic nervous system • s150 Structure of parasympathetic nervous system • s198 Structure of the nervous system, other specified • s199 Structure of the nervous system, unspecified |
|
|
■ Chapter 2: The Eye, Ear, and Related Structures • s210 Structure of eye socket • s220 Structure of eyeball • s230 Structures around eye • s240 Structure of external ear • s250 Structure of middle ear • s260 Structure of inner ear • s298 Eye, ear, and related structures, other specified • s299 Eye, ear, and related structures, unspecified |
• s330 Structure of pharynx • s340 Structure of larynx • s398 Structures involved in voice and speech, other specified • s399 Structures involved in voice and speech, unspecified |
|
|
Activities and Participation |
||
|
■ Chapter 3: Communication • d310—d329 Communicating: receiving • d330-d349 Communicating: producing • d350-d369 Conversation and use of communication devices and techniques • d398 Communication, other specified • d399 Communication, unspecified |
||
|
■ Chapter 3: Structures Involved in Voice and Speech • s310 Structure of nose • s320 Structure of mouth |
||
Reproduced from: International classification of functioning, Disability and Health (ICF). © World Heath Organization.
► A Brief History of Neuroscience
The history of neuroscience has been a quest to answer the question: How does the brain work? One attempt to answer this question has been that the brain works in bits and pieces, having discrete areas that handle specific functions. The other attempt to answer this question has been that it works more holistically (FIGURE 1-9). The holistic proponent would say that the brain works as an integrative whole and cannot be broken down into discrete areas. Having said this, there have been people throughout history who thought the brain did not have anything to do with mental functions. We now embark on a brief history of neuroscience.
Prehistory
Prehistory or prehistoric refers to a period before history was written down, a period prior to about 3500 BCE. What is known about this period comes from various artifacts that have been unearthed. Artifacts that shed light on prehistoric understandings of neuroscience include skulls with holes in them and the instruments used in making these holes, called trephines. These were usually sharp stones used to create holes in skulls through cutting, scraping, and/or drilling. This procedure is known as trephination (FIGURE 1-10). Why would prehistoric people perform such procedures on each other? There is no written history to rely on, so we have to base our ideas on premodern and modern reasons for this procedure. We can guess that prehistoric people performed this procedure to treat headaches, seizures, posttraumatic brain injury, and perhaps even madness or beliefs in evil spirits. The bottom line is that these people knew there was something special about the head region and they continued to perform trephinations, probably because the procedure worked from time to time. For example, it is conceivable that the procedure successfully relieved pressure in the cranial cavity after a traumatic brain injury, bringing improved functioning to the patient.
FIGURE 1-9 The spectrum of belief about brain function.
FIGURE1-10 An example of trephination.
Courtesy of the National Library of Medicine.
Early History
The Egyptians were cardio-centrists, meaning they believed the seat of mental functions was in the organ we call the heart. However, they did make observations about damage to the head leading to physical impairments. The Edwin Smith papyrus (3000-2500 BCE) records 48 medical cases, which include cases involving head and brain injury. Here is an example from case 8:
If thou examinest a man having a smash of his skull . . . thou shouldst palpate his wound. Shouldst thou find that there is a swelling protruding on the outside of that smash which is in his skull . . . on the side of him having that injury which is in his skull; (and) he walks shuffling with his sole, on the side of him having that injury which is in his skull
(Wilkins, 1964)
In this example, the writer is identifying paralysis of one side of the body (i.e., hemiplegia) due to head injury.
Like the Egyptians, the Greeks were cardiocentrists, but the brain did not go completely unnoticed. Hippocrates (460-370 BCE) observed that damage to one side of the brain resulted in problems with the opposite side of the body (FIGURE 1-11). Aristotle (384-322 BCE) correctly theorized localization, the idea that a certain part of the body is responsible for certain mental functions, but he attributed these to the wrong organ, the heart instead of the brain (FIGURE 1-12). What did he believe about the brain? He thought it was a radiator meant to cool the blood, which had been heated up by the heart.
FIGURE1-11 Hippocrates.
Courtesy of the National Library of Medicine.
FIGURE 1-12 Aristotle.
Courtesy of the National Library of Medicine.
Later History
Moving into the Common Era (CE), thinkers shifted their attention from the heart to the head. Two famous Romans, Galen (CE 130-200) and Augustine (CE 354-430), postulated that mental functions were localized in the brain (FIGURE 1-13). Specifically, they believed these functions were localized in the open spaces of the brain known as the ventricles. This belief gave rise to what is known as the cell doctrine, that the cells or ventricles of the brain had psychic gases called humors in them responsible for mental functions. This theory persisted for approximately 1,000 years until the time of the Renaissance, when people like Andreas Vesalius (1514-1564) began to conduct careful studies of brain anatomy and construct detailed drawings, which future scientists would use to more thoroughly study the brain (FIGURE 1-14).
FIGURE1-13 A. Galen. B. Augustine.
A. Courtesy of the National Library of Medicine.
B. © ilbusca/iStockphoto.
Modern History
In the 18th and 19th centuries, focus shifted from the brain ventricles to the brain tissue itself. Phrenologists, like Franz Josef Gall (1758-1828), believed that bumps on people’s scalps were due to raised portions of brain tissue (FIGURE 1-15). These raised portions represented mental strengths, such as memory, math ability, and color perceptions, and personality traits such as agreeableness or combativeness (FIGURE 1-16). This belief led to the development of the profession of phrenology, whose practitioners examined and analyzed people’s skulls in a procedure called cranioscopy (FIGURE 1-17). Phrenologists are examples of radical localizationists, meaning people who believed certain areas (and only those areas) performed certain mental functions. The opposite view, called holism, was presented by Marie-Jean-Pierre Flourens (1794-1867), who asserted that brain function was not so neatly organized. Flourens (FIGURE 1-18) argued that the whole brain, not just a discrete part of the brain, was involved in a mental function.
FIGURE1-14 Andreas Vesalius.
Courtesy of the National Library of Medicine.
FIGURE1-15 Franz Josef Gall performing a cranioscopy.
Courtesy of the National Library of Medicine.
FIGURE 1-16 Phrenology charts.
Courtesy of the National Library of Medicine.
FIGURE 1-17 Phrenologist performing a cranioscopy.
Courtesy of the National Library of Medicine.
FIGURE 1-18 Marie-Jean-Pierre Flourens.
Courtesy of the National Library of Medicine.
In the latter half of the 19th century, a mediating position between localists and holists known as connec- tionism developed. In 1861, Paul Broca (1824-1880) presented a patient nicknamed Tan (because “tan” was the only word he could say intelligibly) to his peers (FIGURE 1-19). Tan demonstrated loss of speech and a right hemiplegia. Tan died shortly after Brocas presentation and his brain was examined, revealing damage to the left frontal portion of the brain known today as Broca’s area (FIGURE 1-20 and BOX 1-2). We know from Broca’s work that Broca’s area is a key area in human speech production. Later, Karl Wernicke (1848-1904) built on Broca’s work by identifying an area in the left posterior portion of the brain responsible for understanding language (FIGURE 1-21 and BOX 1-3). This area eventually was named Wernicke’s area. Both Broca and Wernicke contributed to the idea of connectionism, the belief that there are centers in the brain responsible for certain functions and that these areas are connected and work cooperatively (BOX1-4).
FIGURE1-20 The brain of Leborgne (Tan).
Courtesy of the National Library of Medicine.
BOX 1-2 Paul Broca
The French physician Paul Broca lived in a time of tension in neuroscience. Franz Josef Gall, a phrenologist, and Marie-Jean-Pierre Flourens, a holist, were disputing how the brain worked and where mental faculties were located. Broca helped to bring the controversy to rest through a patient named Leborgne, more famously known as "Tan” because this was the only understandable word he said. When Tan died, Broca did an autopsy and discovered that Tan had a lesion on the third frontal convolution of the left hemisphere. Broca concluded that this particular area was crucial for speech production, and over the course of 2 years he found 12 more cases to substantiate his original findings. This area is known today as Broca's area, and the type of language problem associated with damage to it is known as Broca's aphasia.
FIGURE1-19 Paul Broca.
Courtesy of the National Library of Medicine.
BOX 1-3 Karl Wernicke
Karl Wernicke was born in Germany in 1848 and studied both neurology and psychiatry. Wernicke, spurred on by Broca's work in France, began his own investigation on the effects of neuropathologies on speech and language. In his research, he observed that language disturbances occurred when other areas of the brain were damaged, but Broca's area was left intact. He found an area on the posterior part of the superior temporal gyrus that, when damaged, left patients with difficulty understanding other people's speech and language. From this, Wernicke postulated that this area, known today as Wernicke's area, is crucial for language comprehension. This area of the brain carries his name, as does the form of aphasia associated with damage to it: Wernicke's aphasia.
FIGURE 1-21 Karl Wernicke.
Courtesy of the National Library of Medicine.
BOX 1-4 The Duel
It is easy to think that earlier neuroscientists, like Broca and Wernicke, worked calmly and cooperatively on how the brain works. This was not always the case, however. Joseph Jules Dejerine (1849-1917) is remembered for being one of the first to describe a sudden loss of reading ability, known as alexia. He was a localist in the tradition of Broca and Wernicke. Pierre Marie (1853-1940) was a bitter opponent of Dejerine, accusing Dejerine of poor and substandard work. In response, Dejerine challenged Marie to a duel, thinking his honor had been attacked. The duel never happened. Instead, Marie defused the situation by publishing a letter stating that neither Dejerine's honor nor work was in question. In 1906, the bold Marie even challenged Broca's work from 30 years previously, arguing that Tan's speech loss was due to damage to both Broca's and Wernicke's areas, rather than just Broca's area. Marie's opinion held sway for over 70 years until 1979, when Tan's brain was scanned using computed tomography technology. The findings supported Broca's conclusions and showed that Marie was wrong.
BOX 1-5 Where Are the Famous Neurologists of Today?
Oliver Sacks (1933-2015) was probably the most famous neurologist in recent memory because of his popular writing (FIGURE 1-22) FreightBig Pro. He was born in Great Britain but immigrated to the United States in the 1960s. In 1966 he began work at Beth Abraham Hospital, where he treated survivors of encephalitis lethargica, also known as the "sleeping sickness," which is a disease that became an epidemic in the 1920s. The disease attacks the brain and leaves its victims unable to move or speak. Sacks developed a drug treatment that "unfroze" these patients who had not moved in decades. Sacks wrote a book called Awakenings in which he documented his treatment as well as the patients' temporary recovery. The book was made into a movie of the same name, with Robin Williams playing the role of Sacks. Dr. Sacks published many books of neurological tales, including The Man Who Mistook His Wife for a Hat and An Anthropologist on Mars. Sacks himself suffered from a neurological disorder known as prosopagnosia, or face blindness.
Antonio Damasio (b. 1944) is one of the most famous living neurologists (FIGURE 1-23). He was born in Portugal and studied medicine at the University of Lisbon. He moved to Boston, Massachusetts, and studied under Harold Goodglass at the Aphasia Research Center. One of his main research interests has been the neurobiology of emotions. Two of Damasio's most famous books are Descartes' Error: Emotion, Reason and the Human Brain and The Feeling of What Happens: Body and Emotion in the Making of Consciousness. His wife, Hanna, is also a well-known neuroscientist. Both of the Damasios currently work at the University of Southern California, and they often publish together.
FIGURE1-22 Oliver Sacks.
FIGURE 1-23 Antonio Damasio.
Connectionism of one form or another has dominated neuroscience ever since thanks to scientists such as Roman Jakobson (1896-1982), A. R. Luria (19021977), Norman Geschwind (1926-1984), and Harold Goodglass (1920-2002). Of course, there have continued to be holists holding connectionists responsible to explain the complexities of brain function. Some of these scientists include John Hughlings Jackson (1835-1911), Pierre Marie (1853-1940), Henry Head (1861-1940), and Kurt Goldstein (1878-1965). More recent neurologists have continued to build upon the work of these scientists (BOX 1-5). Various theoretical perspectives discussed in this section are summarized in FIGURE 1-24. Of course, there is more to the debate than just whether the brain works through interconnected centers or as an integrated whole. BOX 1-6 discusses another interesting debate called the mindbrain debate and BOX 1-7 challenges a common myth about the brain’s functioning.
FIGURE 1-24 The range of theoretical perspectives on the brain.
BOX 1-6 The Mind-Brain Debate
Look again at the quote that began this chapter by Dr. Stephen Juan: "Every thought, every action, every deed relies upon this incredible organ [the brain]." What does Dr. Juan mean by "every thought . . . relies"? Is the mind that thinks the same as the brain, or is it different? In other words, can the mind be reduced to brain processes, or are the mind and the brain different substances that interact with one another? This question is known as the mind-brain debate. When it comes to this question, dualists believe that humans possess two entities, a material brain and an immaterial mind; in contrast, monists believe humans possess one entity only, a material brain/mind. For the majority of history, most people held to dualism and believed that humans consist of both a body and a soul and, thus, a brain and a mind. With the growing popularity of neuroscience, however, this view has been challenged by neuroscientists as well as some philosophers and theologians who are now opting for monistic explanations for human composition. It might appear from this discussion that there are only two options—dualism or monism—but there are a variety of views under each category (Green & Palmer, 2010; Huffman, 2013).
BOX 1-7 The 10% Myth
Every year, I quiz my neuroanatomy class about what percentage of their brain they think they use. Inevitably, a majority of the class picks "10%." Where did this myth come from and how does it stay in the public conscience? It probably originated with the American philosopher William James (1842-1910), who believed that humans used only a fraction of their mental potential (not brain), which is a plausible idea. He based this idea on cases of incredibly smart people, like William James Sidis (1898-1944). Named after his godfather, William James, Sidis was considered the smartest man who ever lived because of his remarkable language and mathematical skills. Lowell Thomas, in his 1936 introduction to Dale Carnegie's How to Win Friends and Influence People, added 10% to James' statement and said, "Professor William James of Harvard used to say that the average man develops only 10% of his latent mental ability." In time, "latent mental ability" morphed into "brain" in popular belief, and this myth has been propagated over time through popular media. One recent example is the 2014 movie Lucy, which tells the story of a woman named Lucy who, as the result of experiments, is able to access 100% of her brain's potential. Thanks to unlocking the use her entire brain, Lucy becomes both omnipresent and omniscient. The message of the movie is that we only use 10% of our brains leaving 90% unused, and that if we could harness that 90%, we could become Lucy.
The truth is that we use 100% of our brains every day. Brain imaging has shown this. In addition, we know that damage to a very small part of the brain can lead to catastrophic problems in communication and thinking, like in Alzheimer disease and stroke. Lastly, our brains make up about 2% of our body weight but consume about 20% of the body's oxygen. Why would only 10% of our brains need this much energy? The 10% myth is just that: a myth that makes a good Hollywood story.
► Neuroscience Today
Humans have long desired to see the brain, but early attempts involved opening the cranial vault and removing the brain. Early investigators, like Broca and Wernicke, spent years making careful behavioral observations and then waiting for their subjects to die in order to examine their brains. Postmortem dissection is still the gold standard for some diseases, like Alzheimer disease and chronic traumatic encephalopathy (CTE). CTE is a condition many former professional football players have suffered that can be reliably diagnosed only postmortem. Generally, however, advances beginning in the middle of the 20th century have allowed researchers to examine subjects while they are still alive.
Electrostimulation, or brain mapping, was the first technique that mapped the responses of the living brain to specific behaviors. Brain mapping was typically done as patients with conditions such as severe epilepsy underwent brain surgery to sever the connection between the two cerebral hemispheres. Two major observations from brain mapping were made. First, there is some relationship between a specific area of the brain and a specific experience or behavior. For example, if a certain part of the primary motor cortex is stimulated, then a body part might move. Similarly, if a certain area in the primary sensory cortex is stimulated, the patient might feel something in a part of the body. Second, there is a high degree of individual variation in people’s brains. For example, language is localized in the left hemisphere for most people, but there is a certain subset of people with language in either the right hemisphere or spread between the two hemispheres.
The next important event was the development of the computed tomography (CT) scan in the 1970s. From the 1980s through the present day, there has been a technological explosion of neuroimaging techniques. In the 1990s, techniques were refined, and in the early 2000s, techniques have been combined and further refined.
Even with the technological explosion, there are still two basic imaging techniques, structural imaging and functional imaging. Structural imaging shows the brain’s anatomy. In contrast, functional imaging shows the brain’s activity (i.e., brain physiology)—that is, which brain areas are active under certain circumstances. There is no longer a firm divide between these two types of imaging because structural and functional imaging are being combined to form new, powerful imaging tools.
Structural Imaging Techniques
The standard in neuroimaging before CT was plain x-ray films (i.e., radiography). This technology was used to see dense structures, like bones, but worked poorly for viewing soft tissues like the brain. X-ray films are still used today to see skull fractures or craniofacial abnormalities, but this method needs to be used with caution because it involves exposure to radiation, which can lead to cancer if the patient is overexposed to it (Imbesi, 2009).
Computed tomography (tomo is Greek for “a cutting or section”; graphy is Greek for “a writing”) refined the use of x-ray technology (FIGURE 1-25). CT passes x-rays through the human body that reflect off of different densities of tissue, bone, and fluid in different ways, producing an image (FIGURE 1-26). Structures with higher densities (e.g., bone) show up better than structures with lower densities (e.g., brain tissue). The result is a two-dimensional image, which can be digitally processed into three-dimensional images. The advantages of this technique are that it is commonly used and thus easily accessible, making it a relatively inexpensive procedure. There are at least four disadvantages to using CT technology. First is the reality that the technique uses x-rays, posing a small risk of causing cancer. Second, CT shows anatomy only and not physiology. Third, the clarity of images is an issue when viewing soft tissues of the body because images are sharpest when of dense structures. Fourth, CTs sometimes do not pick up new damage to soft tissues. A CT taken at the time of patient admittance might be negative but when repeated the next day might be positive for tissue changes.
FIGURE1-25 A patient in a CT scanner.
FIGURE1-26 Example of a CT scan.
Courtesy of Constantin Potagas.
Magnetic resonance imaging (MRI) uses a magnetic current to flip protons within the body’s water molecules. The signal that is produced is picked up by the MRI’s receiver coils and the data are then formed into three-dimensional images (FIGURE 1-27). There are different ways to view tissue using MRI, T1-weighted images and T2-weighted images. A T1-weighted image is helpful in examining the structure of the cerebral cortex, whereas a T2-weighted image is useful in detecting swelling, inflammation, and white matter lesions. The main way to tell if you are looking at a T1-weighted versus a T2-weighted image is the color of the brain ventricles. In the former, the ventricles will appear black; in the latter, they will appear white.
FIGURE 1-27 Example of an MRI scan.
The advantages of MRI include a much sharper image (especially of soft tissues) compared to CT. In addition, harmful x-rays are not used, thus eliminating the risk of cancer. Disadvantages include the expense of the test compared to CT, claustrophobic reactions due to the narrow tube the patient enters, and the presence of MRI-unsafe metals in the patient’s body (e.g., cochlear implants, vascular stents, brainaneurysm clips, shrapnel). A sample MRI report can be viewed in BOX 1-8.
As mentioned previously, soft tissues are notoriously difficult to see through imaging techniques. Blood vessels, which are made up of soft tissue (endothelial, connective, and smooth muscular tissue) are difficult to image. However, angiography is an invasive technique that uses iodine as a contrast and x-rays to give excellent pictures of the blood vessels (FIGURE 1-28). It makes possible the diagnosis of conditions, like aneurysms and ischemic strokes, that previously were very difficult to diagnose through neuroimaging. The technique is invasive, meaning there is a risk for bleeding, bruising, clotting, or swelling at the injection site. It also uses x-rays and thus exposes the patient to radiation (Imbesi, 2009).
BOX 1-8 Sample MRI Report
AMERICAN IMAGING CENTER
Patient Name: H. R. Date of Birth: 7/11/1927 MRN: 10247583
At the request of: Charles Smith, MD Age: 86 Sex: M Exam Date: 8/8/2013
MRI BRAIN & SELLA W/WO CONTRAST
CLINICAL HISTORY: The patient complains of bilateral blurred vision with dizziness and unsteadiness for 2 months.
TECHNIQUE: A complete diagnostic set of multiplanar images was acquired using an open-ended, wide-aperture 1.5-Tesla MRI system equipped with high-performance gradients. Turbo parallel processing was employed for enhanced speed. Proprietary sound suppression was provided for patient comfort. Sequence selections, image planes, and slice parameters were adjusted for optimal visualization of regional anatomy and pathology anticipated by the patient's history.
Additional sets of T1-weighted images were obtained following uneventful intravenous injection of 10-cc gradlinium contrast material.
FINDINGS: The sella turcica is normal in size and shows a normal-size pituitary gland with uniform enhancement. The carotid siphon segment of both internal carotid arteries shows mild ectasia and tortuosity with a slight medial coursing on the right creating a lateral defect on the pituitary gland. The pituitary stalk is slightly angled to the left as a result. Optic chiasm is normal. There is no upward convexity at the diaphragm sellae nor is there a suprasellar component.
There is relatively contiguous increase in signal in periventricular white matter adjacent to the lateral ventricles bilaterally with FLAIR and T2 technique nonenhancing with multiple small foci more peripherally situated in the cerebral hemispheres bilaterally with similar signal characteristics. These are all nonenhancing and represent chronic small vessel ischemic changes. There is no mass lesion demonstrated with no shift in midline structures. The ventricles and cortical sulci are within normal limits for age, and there is no extracerebral fluid collection. There is no evidence of acute or chronic lobar or lacunar infarction.
Cranial nerve complex 7 and 8 is normal bilaterally with no evidence of cerebellopontine angle mass lesion.
The paranasal sinuses are well aerated without membrane thickening demonstrated. There has been cataract surgery in the right lobe.
IMPRESSION:
1. There are relatively severe periventricular white matter changes in both cerebral hemispheres representing chronic small vessel ischemic change.
2. There is mild deformity on the pituitary gland due to impression by slightly tortuous carotid siphon segment of right internal carotid artery without gland enlargement or focal lesion within the gland with normal appearance of optic chiasm.
3. There is no intraparenchymal focal mass or active process demonstrated with no abnormal enhancement noted.
Thank you kindly for referring your patient to our office.
Gregory G. Stump, MD
Board Certified Radiologist
FIGURE1-28 A physician observing an angiography.
Functional Imaging Techniques
Functional imaging techniques fall into two categories: spatial resolution and temporal resolution. Spatial resolution identifies the location of brain activity, whereas temporal resolution techniques deal with the time between a stimulus being introduced and the brain’s response to it. Examples from both of these functional imaging categories will be discussed along with their advantages and disadvantages (TABLE 1-1).
Positron emission tomography (PET) is a spatial resolution technology that shows brain activity based on the brain’s glucose metabolism (FIGURE1-29). The underlying assumption of the technique is that active areas require more energy; thus they consume more glucose. A radioactive isotope, which is chemically attached to a glucose molecule, is injected into a patient’s bloodstream. As the isotope decays, it emits photons, which are picked up by the scanner and formed into a threedimensional image. The advantage of this technique is that it gives very useful data on brain activity, but there are disadvantages, including the invasive nature of the technique (i.e., it requires an injection into the bloodstream) and the fact that a radioactive material is used.
TABLE 1-1 Comparison of Spatial and Temporal Resolution Techniques
|
Spatial Resolution: From Best to Worst |
Temporal Resolution: From Best to Worst |
|
Functional magnetic resonance imaging (fMRI) |
EEG |
|
Positron emission tomography (PET) |
fMRI |
|
Electroencephalography (EEG) |
PET |
FIGURE1-29 Example of PET.
Courtesy of the Alzheimer's Disease Education and Referral Center, a service of the National Institute on Aging.
FIGURE1-30 Patient undergoing EEG.
© Daniela Schraml/ShutterStock, Inc.
Electroencephalography (EEG) is a temporal resolution technique that measures the neuronal electrical activity through electrodes placed on the scalp (FIGURE 1-30). As a stimulus is presented to a subject’s senses, the EEG monitors the brain’s electrical responses to that stimulus. The result is a graph that compares electrical activity from each electrode over time (FIGURE 1-31). Advantages of this technique include its relatively low cost, the wide availability of the machines, and the good temporal resolution data the technology delivers. Its disadvantages include the limited spatial resolution EEG provides and its limitations in providing information on activity in deeper layers of the brain.
Combined Structural and Functional Imaging Techniques
As we entered the new millennium, many of the techniques described previously have been combined. For example, functional magnetic resonance imaging (fMRI) combines the advantages of MRI with the advantages of PET, showing both the anatomy and physiology of the brain by measuring blood oxygenation. Advantages include that it does not require the injection of a contrast like PET scans require. In addition, fMRI provides both spatial and temporal resolution data in one test. The main disadvantage is that fMRI is mainly used in research facilities and rarely in clinical settings. With this technology’s advantages, it will likely move more into the mainstream in the near future.
FIGURE 1-31 An EEG graph.
Which Test When?
When a person arrives in the hospital’s emergency department presenting with neurological signs and symptoms, CT is usually the first neuroimaging technique used. Typically, CT is followed up with MRI. Other neuroimaging studies, such as angiography or PET, are ordered if needed. Given the number of neuroimaging techniques available today, how does a neurologist determine which test to order?
The answer is that it depends on what condition is suspected. Remember that a careful neurological exam can tell much about which neurological condition a person may be suffering from. Often, neuroimaging studies are ordered to confirm a preliminary diagnosis already arrived at by the neurologist. If a neurologist suspects a stroke, the best studies to order are CT, MRI, and perhaps angiography. For conditions like aneurysms or arteriovenous malformations, cerebral angiography remains the gold standard, though CT or MRI may also be ordered. Neoplasms (e.g., brain tumors) are best evaluated through CT and MRI, as are central nervous system infections like meningitis. White matter diseases, like multiple sclerosis, are best evaluated through MRI or fMRI. CT and MRI are typically the choice for situations involving trauma to the head. EEG is an excellent tool for evaluating patients with epilepsy, brain tumors, and sleep disorders (Weiner & Goetz, 2004).
You can see that one neuroimaging technique is not necessarily better than another. Each technique is a tool in the neurologist’s tool belt that should be used in just the right situation to give medical professionals the best information possible to diagnose and treat the patient with a neurological problem.
A Caution Regarding Imaging Techniques
Just because we can now “see” into the brain, we are tempted to correlate every possible thought or action with some specific area of the brain that might light up on an image. It must be remembered that because one area of the brain lights up does not mean that it is the sole area responsible for a function. The brain is a highly complicated organ and will probably never be fully understood in all its wonderful complexity.
Neuroimaging techniques (TABLE 1-2) are exciting, continuously developing tools that help us understand the power of the brain. These techniques are very useful in understanding the relationships among the brain, language, and other cognitive functions. It is important for SLPs and audiologists to be familiar with neuroimaging techniques so that they can be good consumers of current research and clinical information. They should also remember Hippocrates’ sage advice about the power of observation and the wisdom of completing a careful, systematic examination of the communication system.
In terms of brain functioning, what was once thought to be a serial and linear process is now thought to be a nonserial, parallel, and highly complicated process. Neuroradiological techniques, like those discussed previously, have allowed us to peer into the brain and glimpse this complexity. This ability has led to various subfields emerging in neuroscience today, including fields such as molecular neuroscience (i.e., the study of important neurological molecules), cellular neuroscience (i.e., the study of neurons and other brain cells), systems neuroscience (i.e., the study of the motor system), behavioral neuroscience (i.e., the study of behaviors such as types of memory), and cognitive neuroscience (i.e., the study of higher level cognitive functions such as language).
► Conclusion
Why is it important to know about theoretical perspectives of brain function like connectionism and holism? The reason is that theoretical perspectives lead to the invention of diagnostic and therapeutic methods. For example, Harold Goodglass (a connectionist) developed a test for aphasia called the Boston Diagnostic Aphasia Examination. This test is based on connectionist ideas and ties types of aphasia to damaged areas in the brain. However, Hildred Schuell developed the Minnesota Test for the Differential Diagnosis of Aphasia from a holist’s perspective. Her test is not concerned with damaged brain areas, but rather with giving basic descriptions of patient strengths and weaknesses in order to plan therapy. As your professors teach you about different theories, always remember that theory matters! In other words, it has real-world implications for tests and therapy procedures and materials.
TABLE 1-2 Summary of Select Neuroimaging Techniques
|
Name |
Structural or Functional |
Positives |
Negatives |
|
Computed tomography (CT) |
Structural |
Inexpensive; commonly used; readily accessible |
Danger of x-rays; structural only; clarity with soft tissues; sometimes do not pick up new damage |
|
Magnetic resonance imaging (MRI) |
Structural |
Sharp, clear image (of soft tissues); no x-rays used |
More expensive than CT; claustrophobic reactions; danger if metals in person's body |
|
Angiography |
Structural |
Excellent pictures of vascular system; can diagnose conditions previously difficult to diagnose |
Invasive (requires injection); uses x-rays (radiation) |
|
Positron emission tomography (PET) |
Functional |
Good data on brain physiology (spatial resolution) |
Invasive (requires injection); radioactive material used in injection |
|
Electroencephalography (EEG) |
Functional |
Low cost; readily available; good temporal resolution |
Limited spatial resolution; lack of information on deep brain structure function |
|
Functional magnetic resonance imaging (fMRI) |
Both |
Provides both structural and functional data; no injection needed; no x-rays used |
Rarely found in clinical settings |
SLPs and audiologists also need to know about neurology because they will be working with people who have communication disorders that have a neurological origin. For example, people with autism make up a large percentage of many SLPs’ caseloads, and this condition has neurological dimensions. It is important to learn and understand the normal nervous system in order to have a baseline for understanding an abnormal nervous system and the various communication disorders that can result (FIGURE 1-32). For example, there are several types of classic aphasias (i.e., an acquired multimodality language loss). It is widely known that damage to the anterior part of the cerebrum can result in certain aphasia types, and damage to the posterior cerebrum results in other types. It is important to understand how the anterior and posterior portions of the cerebrum work in order to understand the signs and symptoms our patients are experiencing. Another example is dysarthria (i.e., slurred and/or discoordinated speech). There are six different types of dysarthria that result from damage to different parts of the nervous system, and the characteristics of these types of dysarthria are different depending on where the damage is in the nervous system.
FIGURE1-32 The importance of neurology to communication disorders.
This is your opportunity to dive in and learn as much as you can about the nervous system so you will be an effective professional in understanding and treating your future patients. In addition, neurology is fun and interesting in its own right!
SUMMARY OF LEARNING OBJECTIVES
The following were the main learning objectives of this chapter. The information that should have been learned is below each learning objective.
1. The learner will define the following terms: neurology, anatomy, physiology, and pathology.
• Neurology is the study of the anatomy, physiology, and pathology of the nervous system.
• Neuroanatomy is the study of the nervous system’s structure.
• Neurophysiology is the study of the nervous system’s function.
• Neuropathology is the study of disease processes that affect both anatomy and physiology of the nervous system.
2. The learner will be able to create an argument as to why speech-language pathologists and audiologists need neurological training.
• Knowing the terminology and abbreviations neurologists use will help SLPs and audiologists decode their language.
• Knowing about the location of brain damage can help with the planning of assessment.
• Knowing about neurological etiologies can help with the prediction of likely patient problems.
• Knowing neurology helps in the documentation of patient improvement and efficacy of treatment methods.
• Knowing about neuroplasticity helps in the careful planning of treatment to take advantage of this phenomenon.
• Having a working knowledge of neurology helps SLPs and audiologists gain the respect of neurologists and other medical professionals.
3. The learner will be able to list various categories of neurological disorders and provide one example in each category.
• Inflammatory diseases: encephalitis and meningitis
• Systematic atrophies of the central nervous system: Huntington disease
• Extrapyramidal and movement disorders: Parkinson disease
• Other degenerative diseases of the nervous system: Alzheimer disease
• Demyelinating diseases of the central nervous system: multiple sclerosis
• Episodic and paroxysmal disorders: epilepsy
• Nerve, nerve root, and plexus disorders: Bell palsy
• Polyneuropathies and other disorders of the peripheral nervous system: Guillain-Barre syndrome
• Diseases of the myoneural junction and muscle: myasthenia gravis
• Cerebral palsy and other paralytic conditions: cerebral palsy and spinal cord injury
• Other disorders of the nervous system: anoxia
4. The learner will be able to draw and explain the spectrum of belief as to how the brain works.
• The brain works in bits and pieces: phrenology.
• The brain is a series of interconnected centers: connectionism.
• The brain works as an integrated whole: holism.
5. The learner will list and define structural and functional imaging techniques and list at least one reason why communication disorders professionals should know about neuroimaging techniques.
• Structural imaging techniques
• X-ray imaging (radiography): technique that uses x-rays to view skull fractures and craniofacial abnormalities
• Computed tomography (CT): use of a computer to convert x-ray images into two- and three-dimensional images
• Magnetic resonance imaging (MRI): use of magnets to flip protons in the body, which is picked up by a computer and converted into an image clearer than CT
• Angiography: technique that uses injected dye to view the vascular system
• Functional imaging techniques
• Positron emission tomography (PET): a spatial resolution technology that shows brain activity based on the brain’s glucose metabolism
• Electroencephalography (EEG): a temporal resolution technique that measures the neuronal electrical activity through electrodes placed on the scalp
• SLPs and audiologists are consumers of the reports generated from these technologies. These reports can be found in journal articles and in patient charts.
KEY TERMS
Activity barriers Alzheimer disease Anatomy Angiography Cell doctrine Computed tomography (CT)
Connectionism Dualists Electroencephalography (EEG) Functional imaging Functional magnetic resonance imaging (fMRI)
Function barriers
Hemiplegia Holism
Incidence
Magnetic resonance imaging (MRI)
Mind-brain debate Monists
Nervous system Neuroanatomy Neurological disorder Neurology Neuropathology Neurophysiology Parkinson disease
Participation barriers Pathology Phrenology Physiology Positron emission technology (PET)
Prevalence Spatial resolution Structural imaging Temporal resolution Trephination Trephines Ventricles
DRAW IT TO KNOW IT
1. Sketch a person and include a simple picture of the brain, spinal cord, and nerves (see Figure1-1). Label these three structures.
2. Draw WHO’s model of health and disability (see Figure 1-4), and apply a medical case you are familiar with to it.
3. Draw the spectrum of views regarding how the brain works (see Figure1-24).
QUESTIONS FOR DEEPER REFLECTION
1. Why are our neurological systems precious resources?
2. Why is theory important?
3. Why should SLPs and audiologists know about the nervous system?
4. Compare and contrast the strengths and weaknesses of each neuroimaging technique.
5. Why should communication disorders professionals be knowledgeable of neuroimaging techniques?
CASE STUDY
A 63-year-old female was admitted to the hospital with sudden right-sided weakness and loss of speech. Her neurologist diagnosed her with a (L) CVA, (R) hemiplegia, and global aphasia.
1. As a speech-language pathologist, why would it be important for you to know the following terms provided by the neurologist: CVA, hemiplegia, global aphasia?
2. Apply the World Health Organization’s International Classification of Functioning, Disability and Health (ICF; Figures 1-4 and 1-5) to this case and answer the following questions:
a. What is this patient’s health condition?
b. How might it affect her function?
c. How might it affect her activities?
d. How might it affect her participation?
e. What might be one environmental factor involved in her case?
f. What might be one personal factor involved in her case?
3. Using the WHO’s ICD-10 section on diseases of the nervous system, which of the 11 categories might this patient’s diagnosis best fit under?
SUGGESTED PROJECTS
1. Think about someone you know who has a neurological disorder (see the section on Classification of Neurological Disorders for ideas). Research 3. this disease and write an essay that includes a description of the disease; its signs, symptoms, and cause(s); the methods by which it is evaluated and treated; and any speech, language, or hearing 4. issues that may be associated with it.
2. Choose a famous person with a neurological disorder and write a case history (i.e., the story of how his or her disease began and has progressed) on the person.
Pick one of the historical figures mentioned in this chapter and write an essay describing the contribution that person made to the field of neuroscience.
Read the sample MRI report (Box 1-8), make a list of unfamiliar terms, and look them up in a medical dictionary.
REFERENCES
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Bertolote, J. M. (2007). Neurological disorders affect millions globally: WHO report. Geneva, Switzerland: World Health Organization. Retrieved from http://www.who.int/mediacentre /news/releases/2007/pr04/en/index.html
Centers for Disease Control and Prevention (CDC). (2018). Autism spectrum disorder (ASD): Data and statistics. Atlanta, GA: CDC. Retrieved from http://www.cdc.gov/ncbddd /autism/data.html
Gooch, C. L. , Pracht, E., & Borenstein, A. R. (2017). The burden of neurological disease in the United States: A summary report and call to action. Annals of Neurology, 81(4), 479-484.
Green, J. B., & Palmer, S. L. (2010). In search of the soul: Four views of the mind-body problem. Eugene: OR: Wipf & Stock.
Hirtz, D., Thurman, D. J., Gwinn-Hardy, K., Mohamed, M., Chaudhuri, A. R., & Zalutsky, R. (2007). How common are the “common” neurologic disorders? Neurology, 68, 326-337.
Huffman, D. S. (2013). An overview of the monism-dualism debate on human composition. La Mirada, CA: Biola University Center for Christian Thought. Retrieved from https://cct.biola .edu/overview-monism-dualism-debate-human-composition/ Imbesi, S. G. (2009). Neuroradiology: Diagnostic imaging strategies. In J. Corey-Bloom & R. David (Eds.), Clinical adult neurology (pp. 53-77). New York, NY: Demos Medical.
Juan, S. (1998). The odd brain: Mysteries of our weird and wonderful brains explained. New York, NY: Angus & Robertson.
LaPointe, L. L. (1977). What the speech pathologist expects from the neurologist. In R. H. Brookshire (Ed.), Clinical aphasiology: Proceedings of the conference 1977 (pp. 5-9). Minneapolis, MN: BRK Publishing.
Manasco, M. H. (2017). Introduction to neurogenic communication disorders (2nd ed.). Burlington, MA: Jones & Bartlett Learning.
Rubens, A. B. (1977). What the neurologist expects from the clinical aphasiologist. In R. H. Brookshire (Ed.), Clinical aphasiology: Proceedings of the conference 1977 (pp. 1-4). Minneapolis, MN: BRK Publishing.
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