Low-pressure shunt 'malfunction' following lumbar puncture in children with shunted obstructive hydrocephalus

Most shunt malfunctions present with signs and symptoms of high intracrania l pressure, and computed tomography scans demonstrate ventricular enlargeme nt. However, several authors have described a rare 'low-pressure' hydroceph alic state in which ventricular enlargement can occur in the face of low, o r even negative, intracranial pressures. We report 2 children with obstruct ive hydrocephalus in whom this 'low-pressure state' followed a lumbar punct ure; in both children, the shunts were functioning properly despite increas ed ventricular size on computed tomography scans, and all symptoms resolved (and the ventricles returned to baseline) following a period of enforced r ecumbency without shunt revision. We hypothesize that subarachnoid cerebros pinal fluid leakage through the puncture site in the lumbar theca decreases the intracranial pressures globally to a point below the opening pressures of the shunt valves. The ventricular cerebrospinal fluid, unable to be dra ined through either the subarachnoid space or the shunt, accumulates within the ventricular system under low pressure. One consistent feature in our 2 patients has been the postural nature of the headaches. We recommend enfor ced recumbency and, if necessary, a blood patch to seal the lumbar leakage. Shunt revision or prolonged external ventricular drainage appears to be un necessary in these patients. Finally, neurosurgeons should be aware of this potential complication.