Perimesencephalic Cistern Obliteration: A CT sign of life-threatening shunt failure

Abstract

Although it is rare that a child dies from shunt malfunction, every experienced pediatric neurosurgeon is aware of patients who precipitously deteriorate on the ward while being observed for diagnostic confirmation of their hydrocephalus or while awaiting scheduled surgery. We are presenting eight cases of shunt malfunction who were arousable on admission and scheduled for shunt revision the following day. A precipitous decline in neurologic status prompted unscheduled emergency shunt revision in each case. In fact, six of the eight patients demonstrated decerebrate posturing just prior to surgery. Three patients had a cardiopulmonary arrest and two of the patients died. Most children had been revised several times before but had never undergone urgent surgery. Their clinical histories were not suggestive of extreme shunt dependence. Most of the older children had headaches for five days or more and the majority had been vomiting for more than 24 hours. Furthermore, there were no physical signs that suggested marginal compliance. No patient had papilledema, and only two children had new eye signs. No pupillary changes were manifest. Review of the CT scans revealed ventriculomegaly with previously documented smaller ventricles. More importantly, the basilar cisterns were not seen on any preoperative scan, but were visible postoperatively in the survivors. To weigh the importance of this observation, we reviewed the histories and CT scans of 50 cases of hydrocephalus randomly taken from the neuroradiology files at Children’s Hospital National Medical Center. Obliteration of the basilar cisterns proved to be a reliable radiographics sign of shunt malfunction requiring emergent attention.