Supratentorial extracerebral cysts in infants and children.

Twelve cases of supratentorial extracerebral cysts in infants and children are reported. Eight were located in the Sylvian fissure, two in the interhemispheric fissue, and two over the convexity of the cerebral hemispheres. Irrespective of their precise location these cysts, in their common, uncomplicated form, give rise to a clinical syndrome different from that recorded in older patients, with a symmetrical macrocrania of a severe degree unassociated with any neurological signs or abnormalities in psychomotor development. Extensive unilateral transillumination of the skull is common (six cases). These features, in association with specific angiographic and pneumoencephalographic findings, make a preoperative diagnosis possible. Extracerebral cysts (either arachnoidal or histologically more complex) should be distinguished from intracerebral cavities which may closely mimic them, even at surgery. The natural history of infatile cysts is studied and serial head-measurements (pre-and postoperative) are presented in five cases. Insufficient knowledge of the spontaneous course and incidence of complications prevents definite statements on the necessity and type of therapy.