Cerebrospinal fluid drainage and dynamics in the diagnosis of normal pressure hydrocephalus

INTRODUCTION: Because of the difficulty in distinguishing idiopathic normal pressure hydrocephalus (INPH) from other neurodegenerative conditions unrelated to cerebrospinal fluid (CSF) dynamics, response to CSF shunting remains highly variable. We examined the utility of CSF drainage and CSF pressure (Pcsf) dynamics in predicting response to CSF shunting for patients with INPH. METHODS: Fifty-one consecutive INPH patients underwent continuous lumbar Pcsf monitoring for 48 hours followed by 72 hours of slow CSF drainage before ventriculoperitoneal shunting. Response to CSF drainage and B-wave characteristics were assessed via multivariate proportional-hazards regression analysis. RESULTS: Improvement in 1, 2, or all 3 INPH symptoms was observed in 35 (69%), 28 (55%), and 11 (22%) patients, respectively, after CSF shunt implantation by 12 months after surgery. A positive response to CSF drainage was found to be an independent predictor of shunt responsiveness (relative risk, 0.30; 95% confidence interval, 0.09-0.98; P = 0.05). There was no difference in Pcsf wave characteristics between the shunt-responsive and -nonresponsive groups, regardless of whether 1-, 2-, or 3-symptom improvement was used to define response to CSF shunting. CONCLUSION: In this study of 51 INPH patients who underwent Pcsf monitoring with waveform analysis and CSF drainage followed by shunt surgery, there was no correlation between specific Pcsf wave characteristics and objective symptomatic improvement after shunt placement. Pcsf monitoring with B-wave analysis contributes little to the diagnostic dilemma with INPH patients. Clinical response to continuous CSF drainage over a 72-hour period suggests a high likelihood of shunt responsiveness.