Atlas of pathophysiology, 2 Edition

Part II - Disorders

Neurologic disorders

Brain Tumors

Brain tumors are abnormal growths that develop after transformation of cells within the brain, cerebral vasculature, or meninges. They're usually referred to as benign or malignant.Malignancy in the brain is graded on the degree of cellularity, endothelial proliferation, nuclear atypia, and necrosis. Highly malignant brain tumors are aggressive tumors that grow and multiply rapidly. Survival and prognosis are directly related to tumor grade. However, even though benign tumors lack aggressiveness, they can be as devastating neurologically depending on their size and location. The most common types of primary brain tumors are gliomas, meningiomas, and pituitary adenomas.

Age Alert

Brain tumors are found in all age-groups, with peaks of incidence occurring in early childhood as well as in people ages 50 to 80.

Causes

·         Unknown in most cases

·         A genetic loss or mutation

·         Prior cranial radiation exposure

Pathophysiology

At the level of the cell nucleus, both positive and negative regulators of growth are necessary for normal control of cell proliferation. The positive regulators, proto-oncogenes, have products that function as growth factors, growth factor receptors, and signaling enzymes. Excessive production may occur that converts proto-oncogenes into oncogenes, resulting in significant neoplastic growth.

Negative regulators of cell growth are called tumor suppressor genes. Suppressor genes inhibit cellular proliferation at the level of the nucleus. The loss of tumor suppressor genes by mutation, deletion, or reduced expression aids in the conversion of normal cells to malignant phenotypes. The excessive stimulation of proto-oncogenes and the lack of inhibition of tumor suppressor genes ultimately lead to neoplastic proliferation. As the tumor grows, edema develops in surrounding tissues and intracranial pressure (ICP) increases. As the tumor continues to grow, it may interfere with the normal flow and drainage of cerebrospinal fluid (CSF), causing an increase in ICP.

The brain compensates for increases by regulating the volume of the three substances in the following ways: limiting blood flow to the head, displacing CSF into the spinal canal, and increasing absorption or decreasing production of CSF.

Signs and symptoms

·         Headache

·         Decreased motor strength and coordination

·         Seizures

·         Altered vital signs

·         Nausea and vomiting

·         Increased ICP

·         Neurologic deficits

·         Diplopia

·         Papilledema

Diagnostic test results

·         Skull X-rays confirm the presence of the tumor.

·         Computed tomography (CT) and magnetic resonance imaging (MRI) show changes in brain tissue density.

·         Magnetic resonance spectroscopy evaluates the neurochemical changes in the bed of the tumor. Elevation in choline is noted in high-grade gliomas, as compared with elevated lactate levels in intracranial abscess.

·         Positron emission tomography evaluates the blood flow patterns in the brain and the tumor, and differentiates normal brain tissue from the tumor.

·         The MRI or CT angiogram evaluates the arterial and venous structures surrounding the tumor.

·         Tissue biopsy confirms the presence of the tumor.

·         Lumbar puncture shows increased CSF pressure, which reflects ICP, increased protein levels, decreased glucose levels and, occasionally, tumor cells in CSF.

Treatment

·         Surgery

·         Radiation

·         Chemotherapy

·         Corticosteroids such as dexamethasone

·         Anticonvulsants such as phenytoin

·         Ranitidine or famotidine

·         Analgesics

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CORONAL SECTION OF THE BRAIN

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