A protocol for a cohort study investigating clinical and radiological features of normal pressure hydrocephalus in South London memory services

<ns3:p>Background Normal pressure hydrocephalus (NPH) is a potentially treatable condition causing dementia. Treatment is through insertion of a ‘shunt’, which improves symptoms and prolongs independence, but NPH may be under-treated. Automated brain imaging measures might have potential to identify NPH. Little is known about NPH presentation in memory clinics. This study investigates the period prevalence of NPH and potential use of imaging biomarkers for NPH, especially callosal angle (CA), in detecting NPH in UK memory services. Methods This cohort study will use retrospective data from South London and Maudsley Clinical Records Interactive Search and linked datasets. The study population will comprise individuals aged ≥60 years with at least one referral to memory services from 2007-2024 (estimated n&gt;20,000). Automated tools will be used to measure imaging biomarkers using routinely collected brain magnetic resonance imaging scans that are electronically linked to health records in a subset of the population (estimated n&gt;5,000). Results We will estimate the period prevalence of NPH in this population. We will evaluate automated measurement tools for imaging features of NPH, describe their distributions, and their variation by covariates (eg. demographics). We hypothesise that people with a diagnosis of NPH will have smaller CA compared to people with a diagnosis of dementia, and that imaging features of NPH will predict future diagnosis of NPH. Depending on our findings, we may undertake more detailed analyses, such as a nested case-control or survival analysis. Conclusions This study will give a first understanding of NPH in UK memory services. It will inform future work to improve identification of NPH, for example through a clinical decision support tool. With rising global dementia rates, research into this potentially treatable condition causing dementia is a priority.</ns3:p>