Clinical analysis of arachnoid cysts in the middle fossa.

This paper describes the clinical picture and radiological findings of 12 cases of "idiopathic" arachnoid cyst in the middle fossa which the authors have encountered during the past 12 years. Their results are as follows. 1) The age of the patient in 10 out of 12 cases was under 15 years of age, and 8 cases were males. The site of the cyst was on the left side in 9 cases. 2) On plain skull radiography, thinning and bulging of the temporal bone by the lesion, elevation of the lesser wing of the sphenoid, and forward projection of the greater wing of the sphenoid were observed in all cases. 3) On cerebral angiography, a characteristic elevation of the middle cerebral artery and hypoplasia of its insular and opercular portion were observed; and in the venous phase, a defect of the middle cerebral vein, backward deviation of the vein of Labbé, and elevation of the vein of Rosenthal were seen. 4) On Metrizamide (Amipaque) CT cisternography, there were two types, one which communicated and the other which did not communicate with the adjacent subarachnoid space.