Effect of Anti-Siphon Devices on Postoperative Outcomes in Idiopathic Normal Pressure Hydrocephalus

Ventriculoperitoneal shunts (VPS) integrated with purported anti-siphon devices (ASDs) were introduced with the goal of reducing the sequelae of overdrainage. We aim to compare the clinical benefit and complications of patients with idiopathic normal pressure hydrocephalus who underwent VPS surgery with or without an integrated ASD.

We retrospectively reviewed 140 patients who underwent a lumbar drain trial for possible idiopathic normal pressure hydrocephalus, 99 of whom underwent VPS surgery. Overdrainage complications included subdural hematoma, subdural hygroma, overdrainage headaches, and surgical interventions for overdrainage. Nonoverdrainage complications included falls with emergency department visit.

Of 99 patients who received shunts, 49 had shunts with integrated ASDs and 50 had standard shunts with programmable valves (opening pressure, 215 mm of water; median follow-up, 14.6 vs. 16.3 months). Clinical response (94% vs. 92%; P = 0.74) and time to final shunt setting (P = 0.83) were similar between cohorts. ASDs were associated with no significant change in overdrainage complications (22% vs. 22%, P = 0.96). Patients with ASDs had no significant differences in rates of individual complications (subdural hematoma: 6% vs. 12%, P = 0.33; subdural hygroma: 8% vs. 4%, P = 0.43; overdrainage headache: 8% vs. 6%, P = 0.70; surgical interventions: 2% vs. 8%, P = 0.22; falls: 2% vs. 10%, P = 0.12). Introduction of ASDs was not associated with a significant increase in time interval free of overdrainage (no special cause signal, <3 standard deviations).

VPSs integrated with ASDs are associated with similar clinical benefit, time to final shunt setting, overdrainage complications, and nonoverdrainage complications compared to shunts without ASDs.