Imaging diagnosis of brain metastasis.

Hematogeneous spread of primary neoplasm can result in central nervous system (CNS) disease burden in various anatomically distinct regions; calvarial, pachymeningeal, leptomeningeal, and intraparenchymal. The choice of imaging modality is dependent on the individual clinical situation, but, largely depends on the patients overall clinical status and the information needed to make treatment decisions. Contrast-enhanced magnetic resonance (MR) imaging is the preferred imaging modality of choice; however, computed tomography (CT) is often utilized as the first-pass screening modality for CNS disease. Despite the superior soft tissue resolution, multiplanar capability, and noninvasive nature of MR imaging, T(1)- and T(2)-weighted sequences are limited to delineating morphologic anatomical deraignment of tissues by tumor. Several physiology based MR imaging sequences have been developed which compliment anatomic MR imaging. Proton magnetic resonance spectroscopic and dynamic susceptibility contrast-enhanced perfusion-weighted imaging are two physiologic sequences which add additional diagnostic information allowing for improved tumor characterization. Common pitfalls in evaluating for metastatic disease burden include the misidentification of non-neoplastic hematomas, remote microvascular ischemia, and acute onset of ischemic stroke. In the pediatric population, CNS metastases are rare; however, the onset of acute neurological symptoms in a child with known primary tumor should prompt imaging of the neuroaxis.