Neurology & Neuroscience

Metastases are among the most common mass lesions in the brain. 20-25% of systemic malignancies show metastases in the CNS and 15% of them will present with neurological symptoms before the diagnosis of the systemic cancer. Among them, 40-60% have an abnormal chest radiograph suggestive of bronchogenic primary or other metastases to the lung. Chest radiography should be included in the workup of any brain mass lesion. Additional imaging modalities such as CT, positron emission tomography (PET), and bone scanning are used to stage the systemic disease. CNS metastasis has many manifestations to the skull, dura, leptomeninges and brain parenchyma. CT underestimates the number of brain lesions even when contrast medium is used. Magnetization transfer imaging, perfusion and diffusion imaging and MR spectroscopy can potentially differentiate between a metastatic lesion from multifocal glioma or lymphoma. Many non-neoplastic neurological diseases can mimic metastatic disease on neuroimaging including MS, pyogenic abscess, toxoplasmosis, cysticercosis, sarcoidosis, tuberculosis, fungal infections, and others. Conversely, several brain metastases, can present in the absence of typical tumefactive lesions. When the diagnosis of a brain metastasis is raised, a thorough assessment of history, a physical examination, and a minimal workup can provide important clues on the nature of the lesion (i.e., neoplastic versus vascular, inflammatory, or infectious lesions) and will avoid missing obvious diagnoses. For practical purposes, decisions should continue to be based on adequate clinical judgment, a high index of suspicion for alternative diagnoses, and concordance among different examinations. Biopsy or surgical resection is indicated for all patients in whom the diagnosis of brain neoplasm could not be confidently excluded.