Symmetry

This chapter examines the causes of symmetric neurologic lesions in toxic and metabolic disease, trauma, neoplastic disease, vascular disease, and infectious disease. The importance of symmetry in diagnosis is emphasized. Symmetry can be a problem for the neurologist; especially on computed tomography (CT) scans, symmetric disease can be difficult to notice on the background of symmetric brain anatomy because the eye more quickly detects a one-sided lesion or multifocal asymmetric lesions than symmetric lesions. Symmetry of brain lesions is important to the clinician because it suggests a toxic, metabolic, or other chemically based cause. Diseases with symmetric pathology but unknown cause probably are chemically based; the clue of symmetry gives investigators an opportunity to pursue various avenues of research.