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Primary brain tumors are diagnosed in approximately 52,000 people each year in the United States. At least half of these tumors are malignant and associated with a high mortality rate. Glial tumors account for about 60% of all primary brain tumors, and 80% of those are malignant neoplasms. Meningiomas account for 25%, vestibular schwannomas 10%, and central nervous system (CNS) lymphomas about 2%. Brain metastases are three times more common than all primary brain tumors combined and are diagnosed in approximately 150,000 people each year. Metastases to the leptomeninges and epidural space of the spinal cord each occur in approximately 3–5% of patients with systemic cancer and are also a major cause of neurologic disability in this population.
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APPROACH TO THE PATIENT: Primary and Metastatic Tumors of the Nervous System
CLINICAL FEATURES Brain tumors of any type can present with a variety of symptoms and signs that fall into two categories: general and focal; patients often have a combination of the two (Table 46-1). General or nonspecific symptoms include headache, cognitive difficulties, personality change, and gait disorder. Generalized symptoms arise when the enlarging tumor and its surrounding edema cause an increase in intracranial pressure or direct compression of cerebrospinal fluid (CSF) circulation leading to hydrocephalus. The classic headache associated with a brain tumor is most evident in the morning and improves during the day, but this particular pattern is actually seen in a minority of patients. Headache may be accompanied by nausea or vomiting when intracranial pressure is elevated. Headaches are often holocephalic but can be ipsilateral to the side of a tumor. Occasionally, headaches have features of a typical migraine with unilateral throbbing pain associated with visual scotoma. Personality changes may include apathy and withdrawal from social circumstances, mimicking depression. Focal or lateralizing findings include hemiparesis, aphasia, or visual field defect. Lateralizing symptoms such as hemiparesis are typically subacute and progressive. A visual field defect is often not noticed by the patient; its presence may only be revealed after it leads to an injury such as an automobile accident occurring in the blind visual field. Language difficulties may be mistaken for confusion. Seizures are a common presentation of brain tumors, occurring in about 25% of patients with brain metastases or malignant gliomas but can be the presenting symptom in up to 90% of patients with low-grade gliomas. Most seizures have a focal signature that reflects their location in the brain and many proceed to secondary generalization. All generalized seizures that arise from a brain tumor will have a focal onset whether or not it is apparent clinically.
NEUROIMAGING Cranial magnetic resonance imaging (MRI) is the preferred diagnostic test for any patient suspected of having a brain tumor and should be performed with gadolinium contrast administration. Computed tomography (CT) should be reserved for patients unable to undergo MRI (e.g., pacemaker). Malignant brain tumors—whether primary or metastatic—typically enhance with gadolinium and may have central areas of necrosis; ...