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

## TL;DR

This study aims to understand how common Normal Pressure Hydrocephalus (NPH) is in memory clinics and how brain scans can help identify it.

## Contribution

The study introduces a protocol to evaluate the prevalence of NPH and the potential of imaging biomarkers like callosal angle in UK memory services.

## Key findings

- The study will estimate the period prevalence of NPH in a large memory clinic population.
- Automated imaging tools will be evaluated for detecting NPH-related features like callosal angle.
- Findings may inform the development of clinical decision support tools for NPH identification.

## Abstract

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.

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>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>5,000).

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.

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.

In this paper, we describe our plans to better understand a treatable condition called Normal Pressure Hydrocephalus (NPH). NPH is a build-up of liquid in the brain. It can lead to dementia, and balance and bladder problems. Treatment is through surgery to place a permanent tube (a ‘shunt’) in the brain to drain liquid into the body. Research has found this is safe and cost-effective. Without a shunt, people with NPH are more likely to develop dementia and die early. NPH may be commonly missed or go untreated.

We plan to find out how common NPH is in services for people with memory problems. This study will use data that has already been collected at South London and Maudsley NHS Trust, a large mental health provider. The study will use clinical information from over 20,000 people aged 60 and older who have been referred to memory services. At least 5,000 people will also have a brain scan.

We will count the number of people with NPH by looking through medical records. We will look for markers of NPH on brain scans. We will find out if people with markers of NPH are diagnosed with NPH, and have symptoms of NPH.

A strength of this study is that it will look at real-life clinical care in a diverse group of people. Despite this, our findings might not apply to other communities. A downside is that this study will rely on information collected as part of routine patient care, so some details might be missing.

It’s important to better understand NPH, as it is a treatable condition causing dementia. This study will give a first overview of NPH in UK memory services. This study could guide future work to support doctors to identify NPH, which could help patients and wider society.