Treatment of secondary tonsillar herniation by lumboperitoneal shunt revision

Background: Idiopathic intracranial hypertension (IIH) is a condition that usually affects young. obese women. Management is aimed at controlling symptoms of increased intracranial pressure (ICP) and prevention of visual failure due to papilledema. A common surgical treatment for IIH is the insertion of a lumboperitoneal shunt (LP shunt). Secondary symptomatic tonsillar herniation is an uncommon side effect following lumbar cerebrospinal fluid diversion. Methods: We present two cases of symptomatic secondary tonsillar herniation, one associated with a syrinx, in patients with IIH following valved LP shunting. Treatment options for this side effect may include transplanting the shunt to the ventricular system or decompression of the foramen magnum. Results: In our cases we elected to alter the construct of the LP shunt by inserting a programmable valve which led to clinical and radiological reversal of the tonsillar herniation as well as a dramatic reduction in an associated syrinx. Conclusions: When faced with LP shunt induced symptomatic secondary tonsillar herniation, consideration may be given to altering LP shunt dynamics, prior to inserting a ventricular catheter into normal sized ventricles or decompressing the posterior fossa.