Primary brain tumors are diagnosed in approximately 52,000 people each year in the United States. At least one-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.
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 379-1). 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.
Table 379-1 Symptoms and Signs at Presentation of Brain Tumors
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Table 379-1 Symptoms and Signs at Presentation of Brain Tumors
|High-Grade Glioma (%)||Low-Grade Glioma (%)||Meningioma (%)||Metastases (%)|
|Impaired cognitive function||50||10||30||60|
|Visual field deficit||—||—||—||7|
Cranial MRI is the preferred diagnostic test for any patient suspected of having a brain tumor, and should be performed with gadolinium contrast administration. CT scan should be reserved for those 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; they are characteristically surrounded by edema of the neighboring white matter. Low-grade gliomas typically do not enhance with gadolinium and are best appreciated on fluid-attenuated inversion recovery (FLAIR) MR images. Meningiomas have a characteristic appearance on MRI as they are dural-based 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, but occasionally there is diagnostic uncertainty based on imaging alone. In such patients a brain biopsy may be helpful in determining a definitive diagnosis. However, when a tumor is strongly suspected, the biopsy can be obtained as an intraoperative frozen section before a definitive resection is performed.
Functional MRI is useful in presurgical planning and defining eloquent sensory, motor, and language cortex. Positron emission tomography (PET) is useful in determining the metabolic activity of the lesions seen on MRI; MR perfusion and spectroscopy can provide information on blood flow or tissue composition. These techniques may help distinguish tumor progression from necrotic tissue as a consequence of treatment with radiation and chemotherapy or identify foci of high-grade tumor in an otherwise low-grade-appearing glioma.
Neuroimaging is the only test necessary to diagnose a brain tumor. Laboratory tests are rarely useful, although patients with metastatic disease may have elevation of a tumor marker in their serum that reflects the presence of brain metastases [e.g., human chorionic gonadotropin (βhCG) from testicular cancer]. Additional testing such as cerebral angiogram, electroencephalogram (EEG), or lumbar puncture is rarely indicated or helpful.
Therapy of any intracranial malignancy requires both symptomatic and definitive treatments. Definitive treatment is based upon the specific tumor type and includes surgery, radiotherapy (RT), and chemotherapy. However, symptomatic treatments apply to brain tumors of any type. Most high-grade malignancies are accompanied by substantial surrounding edema, which contributes to neurologic disability and raised intracranial pressure. Glucocorticoids are highly effective at reducing perilesional edema and improving neurologic function, often within hours of administration. Dexamethasone has been the glucocorticoid of choice because of its relatively low mineralocorticoid activity. Initial doses are typically 12 mg to 16 mg a day in divided doses given orally or IV (both are equivalent). While glucocorticoids rapidly ameliorate symptoms and signs, their long-term use causes substantial toxicity including insomnia, weight gain, diabetes mellitus, steroid myopathy, and personality changes. Consequently, a taper is indicated as definitive treatment is administered and the patient improves.
Patients with brain tumors who present with seizures, require anticonvulsant drug ...