102 - Intracranial and Other Central Nervous System Lesions

ventricular system can be manifested as changes in intracranial pressure (ICP) and thus affect the clinical findings. However, slow-growing lesions of a primary CNS origin located in clinically silent regions of the brain such as the frontal lobe may be present for years before detection. Autopsy diagnosis reveals that nearly 25% of patients who die of cancer had intracranial metastasis (Fig. 102.1). The lung is the most common origin of brain metastases. Breast cancer (especially ductal carcinoma) has a propensity to metastasize to the cerebellum and the posterior pituitary gland; however, breast cancer that metastasizes to bone tends to not metastasize to the brain. Other common origins of brain metastases are gastrointestinal malignancies (most commonly colon and rectum), renal carcinoma, and melanoma. In contrast, prostate, esophageal, and ovarian cancer and Hodgkin disease rarely metastasize to the brain. Although metastatic disease is a common form of intracranial mass lesion, other mass lesion considerations include lymphoma (Fig. 102.2), glioblastoma multiforme (Fig. 102.3), astrocytoma, ependymoma, meningioma, oligodendroglioma, • A comprehensive patient history is imperative to narrow the differential diagnosis when a new mass lesion is discovered on radiographic imaging. • A complaint of dizziness requires cerebellar testing, including finger-nose, heel-shin, dysdiadochokinesia, and gait evaluation. • Fever in the setting of a neurologic complaint requires both a neurologic examination and consideration of neuroimaging. • Any patient with a first-time seizure warrants a non– contrast-enhanced computed tomography (CT) scan of the head regardless of age (Box 102.1). • CT scans reliably demonstrate lesions 1.0 cm or larger. • Magnetic resonance imaging should be performed if there is significant concern for a central nervous system lesion in patients with negat ive CT findings. KEY POINTS