Descending transtentorial herniation, a rare complication of the treatment of trapped fourth ventricle: case report.

Descending transtentorial herniation (DTH) is a complication of raised pressure in the supratentorial compartment, usually resulting from mass lesion of several etiologies. The authors report an exceptional case of DTH complicating the implant of a CSF shunting device in the trapped fourth ventricle of a 17-year-old boy in whom a second CSF shunting device had been implanted for neonatal posthemorrhagic and postinfectious hydrocephalus. The insidious clinical and radiological presentation of DTH, mimicking a malfunction of the supratentorial shunt, is documented. Ultimately, the treatment consisted of removal of the infratentorial shunt and endoscopic acqueductoplasty with stenting. The absence of supratentorial mass lesion and other described etiologies of DTH prompted the authors to speculate on the hydrodynamic pathogenesis of DTH in the present case.