MRI - Arachnoid cyst: This 44-year-old man presented with a generalized convulsion. Examination was unremarkable with the exception of slight left-sided hemiparesis and hyperreflexia. The T1-weighted (left panel) and T2-weighted (right panel) axial images show a right frontotemporal cystic lesion that is high signal on T2-weighting and low signal on T1-weighting. The medial rim is lined by gray matter and there is slight midline shift and effacement of the right lateral ventricle.