CPT-3 in Normal Pressure Hydrocephalus

Overview

The study will collect prospective cohort data of individuals that are undergoing routine clinical care for suspected idiopathic Normal Pressure Hydrocephalus (NPH). The administration of the Conner's Continual Performance Test - version 3 (CPT-3), an automated 14-minute computerized measure of reaction-time and sustained attention, will be added to the current neurocognitive screen being used (i.e., the Montreal Cognitive Assessment, MoCA) along with gait assessment. Patients will undergo pre-tap testing on the morning of their large volume Lumbar Puncture (CSF-TT). These patients will receive post-tap CPT-3 and MoCA testing one-to-three hours post-tap, and again at 2-3 days post-CSF-TT, during the follow-up appointment in clinic. The standard NPH quantitative assessment methods of MoCA and gait evaluation will continue to be collected. For those patients that ultimately undergo ventricular shunt placement, the CPT-3 will be administered at their post-operative follow-up appointment (\~3 months post-operation). The results of CPT-3 will not factor into consideration for shunt candidacy.

Normal pressure hydrocephalus (NPH) is a syndrome involving the clinical triad of gait disturbance, urinary incontinence, and cognitive dysfunction, in the context of ventricular enlargement out of proportion to parenchymal atrophy with normal intracranial pressure. In the 1980's, a protocol for quantitative measurement of symptom response to large volume CSF tap (40-50ml) was developed, as a method for evaluating suitability for undergoing ventricular shunting surgery. A 2016 systematic review of the literature noted heterogeneous findings within the eight prospective cohort studies that were included in analysis, but concluded that there appeared to be support for the CSF-TT as a rule-in screen for response to shunt placement. Unfortunately, no extant literature has analyzed the independent predictive power of a clinically significant reaction time improvement in response to CSF-TT (widely defined across the literature as 5% improvement) to subsequent response to ventricular shunting. This frustrates an a priori power analysis. However, a rough estimate was calculated based on data presented within one of the aforementioned reviewed studies that identified an improvement in reaction time in response to CSF-TT, as well as an improvement in reaction time to subsequent shunting. The authors reported that 17 of 68 (25%) of the patients were labeled as positive-responders to CSF-TT, defined as meeting at least 2 of the following criteria: 1) 5% improvement in reaction time, 2) 5% improvement in gait (time or steps), 3) 25% improvement on visuospatial recall task, 4) 25% improvement on visuospatial recognition task. Of those 17 positive responders, 16 (94%) met the same positive-response criteria, post-shunting. If we use a 50% response rate as a proportion null hypothesis, this gives us a z-statistic = 3.63, or f2 = 3.71. G\*Power analysis, for a 4-predictor regression (i.e., the aforementioned indicators used), estimates a necessary sample size of 16. The primary limitation of this approach is that it is unclear which of the 2+ positive response criteria were met. However, review of the pre- versus post-shunting data suggests reaction time was significantly improved (p\<0.001; Cohen's d = 0.399), suggesting it is reasonable to infer the domain was favorably impacted by the temporary effects of a CSF-TT. Patients will undergo pre-tap testing on the morning of their CSF-TT. The administration of the Conners Continual Performance Test - version 3 (CPT-3), an automated 14-minute computerized measure of reaction-time and sustained attention, will be added to the current neurocognitive screen being used (i.e., the Montreal Cognitive Assessment, MoCA). The current CSF-TT protocol's quantitative methods for measuring urinary incontinence and gait will continue to be collected. These patients will receive post-tap CPT-3 and MoCA testing one-to-three hours post-tap, and again at 2-3 days post-CSF-TT, during the follow-up appointment with Neurosurgery. For those that undergo ventricular shunt placement, the CPT-3 will be administered at their post-operative follow-up appointment (\~3 months post-operation).