Weight loss and a shunt on "off": an odd case of overshunting in an idiopathic intracranial hypertension patient. Illustrative case.

In the setting of low-pressure headaches in an IIH patient with a functioning shunt, reductions in intra-abdominal pressure from weight loss can increase anterograde flow through the shunt. Additionally, the Certas programmable valve at its highest setting remains patent, but with a high opening pressure, potentially allowing for overdrainage due to the siphoning effect. Finally, ICP monitoring and headache diaries can significantly aid in the characterization of low-pressure headaches, and shunt ligation can be a curative solution. https://thejns.org/doi/10.3171/CASE25106.