A 33 year-old woman presented with complex partial seizures which often generalized.
Axial CT scans. Note the large cystic lesion in the left anterior-medial temporal and frontal lobes. Also, note in the lower images, most mass effect on the left hemisphere (i.e., the frontal lobe is compressed and smaller on the left the pineal gland is slightly shifted from left to right. This is an arachnoid cyst, a common congenital malformation. The most common locations are the sylvian fissure and middle cranial fossa (as in this case above), suprasellar cistern, quadrigeminal cistern, cerebellopontine angle, posterior infratentorial midline, cerebral convexity and interhemispheric fissure. Most are asymptomatic and are found as an incidental finding. Rarely, they can enlarge and present as a mass lesion with focal neurologic signs, seizures or hydrocephalus.
The Electronic Curriculum is copyrighted 1998, Case Western Reserve University School of Medicine.