Volumes and velocities: Meta-analysis of PC-MRI studies in normal pressure hydrocephalus.

Abstract

Our protocol was prospectively registered on PROSPERO [CRD42020180826]. We systematically searched four databases: Pubmed, Web of Science, Ovid, and Cochrane library to identify all eligible studies. Quality assessment was performed using a modified Newcastle-Ottawa Scale [19]. Systematic review was conducted according to Prisma guidelines. A random-effects model was used to perform meta-analysis on the available flow parameters. Eighteen records were identified for inclusion. Five studies were eligible for meta-analysis, representing 107 iNPH patients and 82 controls. CSF flow parameters available for analysis were stroke volume and peak velocity. Both were significantly higher than controls (p = 0.0007 and p = 0.0045 respectively) according to our random-effects analysis, consistent with a model of hyper-dynamic CSF in iNPH. Our systematic review revealed average stroke volumes in iNPH ranging from 43uL to over 200uL. Peak velocity values ranged from 5.9cm/s to 12.8cm/s. Significant increases in stroke volume and peak velocity values in iNPH patients suggest a place for PC-MRI as supplementary evidence in the diagnostic work-up of iNPH. Although shunting reduces aqueductal stroke volume and peak velocity, the ability of pre-shunt values to reliably predict treatment response remains complicated. We suggest that it may be more appropriate to consider a range of values that reflect varying probabilities of shunt success. We recommend that future studies should prioritise standardising PC-MRI protocols, and before then PC-MRI findings should be considered supportive rather than determinative.