Predictive value of quantitative pupillometry in patients with normal pressure hydrocephalus undergoing temporary CSF diversion

Background: Lumbar drain (LD) trials are used to temporarily divert CSF in order to predict clinical improvement prior to definitive CSF diversion in patients with a diagnosis of normal pressure hydrocephalus. New technology has improved clinical detection of subtle pupillary changes that may occur during CSF diversion trials. The aim of this study was to determine whether pupillary light response as recorded by automated pupillometry could be used to predict response during lumbar drain trials. Methods: The authors prospectively gathered quantitative pupillometry data on admission and following each CSF diversion in a cohort of 30 consecutive patients with a presumptive diagnosis of normal pressure hydrocephalus admitted to a university hospital for elective LD trial between January 1, 2020 and March 30, 2021. The value of pupillometry in predicting success of lumbar drainage in alleviating symptoms was correlated to clinical improvement during lumbar drainage. Results: Of the 29 patients undergoing a 4-day LD trial, 16 (55.2%) demonstrated clinical improvement. Pre-drainage pupillometry values did not differ between patients who had clinical improvement or no clinical improvement. Constriction velocity improved compared to baseline in patients who had a successful lumbar drain trial (LD +). There was a non-significant trend towards improved constriction velocity and improved dilation velocity found in patients even after the first aliquot drainage. Discussion: Baseline pupillary function by automated pupillometry did not predict clinical improvement during lumbar drain trials. Improvement in constriction and dilation velocity may be useful to monitor at the outset, after the initial drainage, and at completion of lumbar drain trials.