719 Ventriculoperitoneal Shunting for Idiopathic Normal-pressure Hydrocephalus: Predictors of Treatment Response and Analysis of Long-term Outcomes

Abstract

INTRODUCTION: Because of the difficulty in distinguishing idiopathic normal-pressure hydrocephalus (INPH) from other neurode-generative conditions unrelated to cerebrospinal fluid (CSF) dynamic pathology, outcome after CSF shunting for presumed INPH remains highly variable. Whereas secondary NPH often responds to shunting, INPH is still considered by most to be an untreatable disease. We set out to elucidate predictors of outcome and characterize long-term outcome after CSF shunting for INPH. METHODS: INPH patients with computed tomography-documented hydrocephalus, normal opening lumbar-puncture CSF pressure, two clinical features of INPH (gait, urinary, or dementia), demonstrating frequent B waves on continuous lumbar CSF pressure monitoring, and improving with 3-day trial of lumbar CSF drainage underwent CSF shunting. Patients were clinically followed up for 1, 3, 6, and 12 months after surgery. RESULTS: One hundred thirty-two patients underwent 179 shunt surgeries; 44 (33%), 79 (60%), and 99 (75%) patients experienced symptomatic improvement 3, 6, and 24 months after shunting. Gait improvement was the first clinical response in 88 patients (93%) responding to CSF shunting. Dementia and urinary incontinence were twofold less likely to improve versus gait abnormalities (RR, 0.49; 95% CI, 0.4–0.9). Radiological evidence of corpus callosum impingement (RR, 1.64; 95% CI, 1.05–2.58), gait pathology as the primary symptom (RR, 1.91; 95% CI, 1.04–3.49), and decreasing duration of INPH symptoms in years (RR, 1.15; 95% CI, 1.04–1.27) were associated with improvement after CSF shunting. In multivariate analysis, duration of symptoms (RR, 0.89; 95% CI, 0.82–0.98) and gait as the primary deficit (RR, 1.87; 95% CI, 1.02–3.43) were independent predictors of outcome after CSF shunting for NPH. CONCLUSION: Shunting INPH patients with B waves on CSF pressure monitoring who improve with 3-day CSF drainage resulted in symptomatic improvement in the majority of cases (75%). Corpus callosum impingement on magnetic resonance imaging, gait abnormalities as the primary symptom, and shorter duration of symptoms predicted improvement with CSF shunting. This series of shunted INPH patients is the largest to date and dispels the notion that INPH is an untreatable disease.