Primary brain tumors are diagnosed in ~78,000 people each year in the United States. At least 25,000 are malignant, and most of these are gliomas. Meningiomas account for 35%, vestibular schwannomas 10%, and central nervous system (CNS) lymphomas ~2%. Brain metastases are three times more common than all primary brain tumors combined and are diagnosed in ~150,000 people each year. Metastases to the leptomeninges and epidural space of the spinal cord each occur in ~3–5% of patients with systemic cancer and are also a major cause of neurologic disability.
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 86-1). General or nonspecific symptoms include headache, with or without nausea or vomiting, 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 compression of cerebrospinal fluid (CSF) circulation leading to hydrocephalus. The classic brain tumor headache predominates in the morning and improves during the day, but this pattern is seen only in a minority of patients. 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 situations, mimicking depression. Focal or lateralizing findings include hemiparesis, aphasia, or visual field defect. Lateralizing symptoms are typically subacute and progressive; language difficulties may be mistaken for confusion. Seizures are common, occurring in ~25% of patients with brain metastases or malignant gliomas and are the presenting symptom in up to 90% of patients with a low-grade glioma. All 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) scan should be reserved for those patients unable to undergo MRI. Malignant brain tumors—whether primary or metastatic—typically enhance with gadolinium, have central areas of necrosis, and are surrounded by edema of the neighboring white matter. Low-grade gliomas usually do not enhance with gadolinium and are best appreciated on fluid-attenuated inversion recovery (FLAIR) MRIs. Meningiomas have a typical appearance on MRI because they are dural-based enhancing tumors with a dural tail and compress but do not invade the brain. Dural metastases or a dural lymphoma can have a similar appearance. Imaging is characteristic for many primary and metastatic tumors and sometimes will suffice to establish a diagnosis when the location precludes surgical intervention (e.g., brainstem glioma). Functional MRI is useful in presurgical planning to define eloquent sensory, motor, ...