Symmetry in computed tomography of the brain: the pitfalls

Computed tomography (CT) studies of the brain are one of the most frequent examinations interpreted by radiologists out of hours. Apparently normal appearances in patients with significant neurological morbidity can be perplexing. As the contents of the cranium are normally remarkably symmetrical on axial CT, disease entities that result in symmetrical appearances are the most difficult to detect. In this review we highlight a spectrum of important acute neurological conditions that result in abnormal but symmetrical appearances on CT.