Tintinalli's Emergency Medicine - Just the Facts, 3ed.

149. CHRONIC NEUROLOGIC DISORDERS

Sarah Andrus Gaines

AMYOTROPHIC LATERAL SCLEROSIS

EPIDEMIOLOGY

images The typical time of onset for amyotrophic lateral sclerosis (ALS) is over age 50 years.

PATHOPHYSIOLOGY

images ALS is caused by upper and lower motor neuron degeneration without other central nervous dysfunction.

CLINICAL FEATURES

images Upper motor neuron dysfunction causes limb spastic-ity, hyperreflexia, and emotional lability.

images Lower neuron dysfunction causes limb muscle weakness, atrophy, fasciculations, dysarthria, dysphagia, and difficulty in mastication.

images Symptoms are often asymmetric.

images Patients may initially have cervical or back pain consistent with an acute compressive radiculopathy.

images Respiratory muscle weakness causes progressive respiratory depression.

DIAGNOSIS AND DIFFERENTIAL

images The diagnosis is clinical and is often previously established.

images Electromyography (EMG) is the most useful test.

images Other illnesses that should be considered include myasthenia gravis (MG), diabetes, thyroid dysfunction, vitamin B12 deficiency, lead toxicity, vasculitis, and central nervous system (CNS) or spinal cord tumors.

EMERGENCY DEPARTMENT CARE AND DISPOSITION

images Emergency care is required for acute respiratory failure, aspiration pneumonia, choking episodes, or trauma from falls.

images The treatment goal is to optimize pulmonary function through the use of nebulizer treatments, steroids, antibiotics, or endotracheal intubation.

images Admit patients with impending respiratory failure, pneumonia, inability to handle secretions, and worsening disease process that may require long-term care.

MYASTHENIA GRAVIS

EPIDEMIOLOGY

images Peak age of onset for myasthenia gravis (MG) is in the second or third decade of life for females and in the fifth or eighth decade for males.

PATHOPHYSIOLOGY

images MG is an autoimmune disease caused by antibody destruction of the acetylcholine receptors at the neuromuscular junction, which results in muscle weakness.

images The thymus is abnormal in 75% of patients and thymectomy resolves or improves symptoms in most patients, especially in those with a thymoma.

CLINICAL FEATURES

images Most MG patients have generalized weakness, specifically of the proximal extremities, neck extensors, and facial or bulbar muscles. There is usually no deficit in sensory, reflex, and cerebellar function.

images Ptosis and diplopia are the most common symptoms. Symptoms usually worsen as the day progresses or with muscle use (eg, prolonged chewing or reading) and improve with rest. Ten percent of patients have ocular muscle weakness only.

images Myasthenic crisis is a life-threatening condition involving extreme weakness of the respiratory muscles that may progress to respiratory failure.

DIAGNOSIS AND DIFFERENTIAL

images The diagnosis is confirmed through administration of edrophonium (Tensilon test), electromyogram, and serum testing for acetylcholine receptor antibodies.

images The differential diagnosis includes Lambert-Eaton syndrome, drug-induced disorders (eg, penicilla-mines, aminoglycosides, and procainamide), ALS, botulism, thyroid disorders, and other CNS disorders (eg, intracranial mass lesions, stroke).

EMERGENCY DEPARTMENT CARE AND DISPOSITION

images Implement supplemental oxygen and aggressive airway management with myasthénie crisis.

images Avoid depolarizing and nondepolarizing paralytic agents. Etomidate, fentanyl, or propofol can be used.

images If the Tensilon test is positive, then administer pyri-dostigmine (60-90 milligrams PO or 2-3 milligrams IV every 4 hours), with an onset of 15 to 30 minutes and duration for 3 to 5 hours. An alternative is neostigmine (0.5 milligram IV), which will be effective within 30 minutes and last for 4 hours.

images Steroids, immunosuppressive medications, and plas-mapheresis may be used in consultation with a neurologist.

images Several drugs should be used with caution in patients with MG (Table 149-1).

images Consult a neurologist for disposition and admission.

TABLE 149-1 Drugs That Should Be Avoided in Myasthenia Gravis

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MULTIPLE SCLEROSIS

EPIDEMIOLOGY

images Three clinical courses are seen in multiple sclerosis (MS): relapsing and remitting (up to 90% of cases); relapsing and progressive; or chronically progressive.

images Peak age of onset is the third decade of life. Females are two to three times more likely to contract MS than are males.

PATHOPHYSIOLOGY

images Although the etiology of MS is unknown, it involves multifocal areas of CNS demyelination, causing motor, sensory, visual, and cerebellar dysfunction.

CLINICAL FEATURES

images Deficits associated with MS are described as a heaviness, weakness, stiffness, or numbness of an extremity or clumsiness. Lower extremity symptoms are usually more severe.

images Lhermitte’s sign is an electric shock-like sensation, a vibration, or dysesthetic pain going down into the arms or legs from neck flexion.

images Physical examination may reveal decreased strength, increased tone, hyperreflexia, clonus, decreased proprioception, reduced pain and temperature, and a positive Babinski reflex.

images Increases in body temperature, associated with exercise, hot baths, or fever, may worsen symptoms.

images Optic neuritis, usually causing unilateral loss of central vision, is the first presenting symptom in up to 30% of cases and may cause an afferent papillary defect (Marcus Gunn pupil).

images Acute bilateral internuclear ophthalmoplegia (INO), which causes abnormal adduction and horizontal nystagmus, is highly suggestive of MS.

images Retrobulbar or extraocular muscle pain usually precedes vision loss. Fundoscopy is usually normal, but the disc may appear pale.

images Rarely, acute transverse myelitis may occur. Cerebellar lesions may cause intention tremor or ataxia. Brain stem lesions may cause vertigo.

images Cognitive and emotional problems are common (eg, mood disorders or dementia).

images Dysautonomia causes vesicourethral, gastrointestinal tract, and sexual dysfunction.

DIAGNOSIS AND DIFFERENTIAL

images The diagnosis of MS is clinical and is suggested by two or more episodes, lasting days to weeks, causing dysfunction that implicates different sites in the white matter.

images MRI of the brain may demonstrate various abnormalities, including discrete lesions in the supratentorial white matter or periventricular areas.

images Cerebrospinal fluid (CSF) protein and gamma-globulin levels are often elevated.

images The differential diagnosis includes systemic lupus erythematosus, Lyme disease, neurosyphilis, and HIV disease.

EMERGENCY DEPARTMENT CARE AND DISPOSITION

images Treat severe motor or cerebellar dysfunction with steroids: high-dose pulsed intravenous methylprednisolone (250 milligrams IV every 6 hours), followed by a PO prednisone taper.

images Fever must be reduced to minimize symptoms. Perform a careful search for a source of infection. Evaluate for acute UTI or pyelonephritis; postvoid residuals >100 mL require intermittent catheterization.

images Respiratory infections and distress must be aggressively managed.

images Admission is required for those at risk for further complications, respiratory compromise, depression with suicidal ideation, and those requiring IV antibiotics or steroids.

LAMBERT-EATON MYASTHENIC SYNDROME

images Lambert-Eaton myasthenie syndrome is an autoimmune disorder that causes fluctuating proximal limb muscle weakness and fatigue.

images Lambert-Eaton syndrome is seen mostly in older men with lung cancer.

images Strength is improved with sustained activity.

images Patients complain of myalgias, stiffness, paresthesias, metallic tastes, and autonomic symptoms (eg, impotence and dry mouth). Eye movements are unaffected.

images The EMG is abnormal and serum tests are specific for antibodies to voltage-gated calcium channels.

images Treatment of the underlying neoplasm greatly improves symptoms.

images Pyridostigmine and immunosuppressive drugs may reduce symptom severity.

PARKINSON’S DISEASE

EPIDEMIOLOGY

images The average age of onset for Parkinson’s disease (PD) is 55 to 60 years of age.

PATHOPHYSIOLOGY

images The etiology of PD is unknown, but patients have reduced functional dopaminergic receptors in the substantia nigra.

CLINICAL FEATURES

images PD presents with four classic signs (mnemonic “TRAP”): resting tremor, cogwheel rigidity, akinesia or bradykinesia, and impaired posture and equilibrium.

images Other signs include facial and postural changes, voice and speech abnormalities, depression, and muscle fatigue.

images Initially, most complain of a unilateral resting arm tremor, described as pill rolling, or a general feeling of stiffness or slowness, which may have been present for years.

DIAGNOSIS AND DIFFERENTIAL

images The diagnosis is clinical and is most often previously established. No laboratory test or neuroimaging study is pathognomonic.

images Parkinsonism can result from street drugs, toxins, neuroleptic drugs, hydrocephalus, head trauma, and other rare neurologic disorders.

EMERGENCY DEPARTMENT CARE AND DISPOSITION

images PD patients may be on medications that increase central dopamine (eg, levodopa, carbidopa, and amantadine), anticholinergics (eg, benztropine), and dopamine receptor agonists (eg, bromocriptine).

images Medication toxicity includes psychiatric or sleep disturbances, cardiac dysrhythmias, orthostatic hypotension, dyskinesias, and dystonia.

images With significant motor or psychiatric disturbances (eg, hallucinations or frank psychosis) or decreased drug efficacy, a “drug holiday” for 1 week should be initiated in consultation with a neurologist.

POLIOMYELITIS AND POSTPOLIO SYNDROME

EPIDEMIOLOGY

images Poliomyelitis leads to paralysis in less than 5% of infected patients.

PATHOPHYSIOLOGY

images Poliomyelitis is caused by an enterovirus that causes paralysis via motor neuron destruction and muscle denervation and atrophy.

images In developed countries, transmission is oral to oral; however, transmission is fecal to oral in developing countries.

CLINICAL FEATURES

images Most symptomatic patients have only a mild viral syndrome and no paralysis. Symptoms include fever, malaise, headache, sore throat, and gastrointestinal symptoms.

images Spinal polio results in asymmetric proximal limb weakness and flaccidity, absent tendon reflexes, and fasciculation. Maximal paralysis occurs within 5 days.

images Other sequelae include bulbar polio (speech and swallowing dysfunction) and encephalitis.

images Postpolio syndrome is the recurrence of motor symptoms after a latent period of several decades.

images Symptoms of postpolio syndrome may include muscle fatigue, joint pain, or weakness of new and previously affected muscle groups. Patients may have new bulbar, respiratory, or sleep difficulties.

DIAGNOSIS AND DIFFERENTIAL

images Consider the diagnosis of polio in patients with an acute febrile illness, aseptic meningitis, and asymmetric flaccid paralysis.

images CSF may reveal a pleocytosis (mostly neutrophils) and positive cultures for poliovirus.

images Throat and rectal swabs are higher yield tests than CSF.

images The diagnosis of postpolio syndrome is based on a prior history of paralytic polio with recovery and new symptoms.

images The differential diagnosis includes Guillain–Barré syndrome, peripheral neuropathies (eg, mononucleosis, Lyme disease, and porphyria), abnormal electrolyte levels, toxins, inflammatory myopathies, and other viruses (eg, coxsackievirus, mumps, echovirus, and various enteroviruses).

EMERGENCY DEPARTMENT CARE AND DISPOSITION

images Treatment is supportive.

images Lamotrigine may improve quality of life.

images Disposition should be made in consultation with a neurologist.


For further reading in Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 7th ed., see Chapter 167, “Chronic Neurologic Disorders,” by Edward R Sloan, Daniel A. Handel, and Sarah Andrus Gaines.