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. 2025 Apr 22;7(1):e001103.
doi: 10.1136/bmjno-2025-001103. eCollection 2025.

Fundoscopy as a diagnostic biomarker in idiopathic normal pressure hydrocephalus: a pilot study

Mathias Just Nortvig  1   2 , Niclas Lynge Eriksen  1   2 , Mikkel C Schou Andersen  1   2 , Emma Tubæk Nielsen  1   2 , Sune Munthe  1   2 , Christian Bonde Pedersen  1   2 , Frantz Rom Poulsen  1   2
Affiliations

Fundoscopy as a diagnostic biomarker in idiopathic normal pressure hydrocephalus: a pilot study

Mathias Just Nortvig et al. BMJ Neurol Open. .

Abstract

Background: Idiopathic normal pressure hydrocephalus (iNPH) has a prevalence of approximately 5%. It is characterised by Hakim's triad of impaired gait, cognitive dysfunction and urinary incontinence. Despite radiological markers and liquor-dynamic tests, iNPH is difficult to diagnose due to many overlapping symptoms. The aim of this study was to evaluate funduscopy as a noninvasive method of screening patients with suspected iNPH.

Methods: Patients with suspected iNPH who underwent a lumbar infusion test (LIT) were included. Funduscopy was performed before the start of the LIT, and intracranial pressure (ICP) was continually measured via lumbar cannulation. Retinal images were analysed using an artificial intelligence algorithm to determine the arteriole-venule (A/V) ratio. The A/V ratio and ICP measurements were compared with the iNPH diagnosis. In addition, the mean difference in shunt response was evaluated.

Results: A significantly lower mean A/V ratio was found in the iNPH group compared with the non-iNPH group (p value: 0.02). Receiver operating characteristic curve analysis with an area under the curve of 0.75 showed a sensitivity of 88% and a specificity of 50% with an A/V cut-off of 0.86. Although not statistically significant, the mean A/V ratio was lower in the group with clinical shunt effect compared with those without (p value: 0.305).

Conclusions: This study found a statistically significant difference in baseline A/V ratios between iNPH and non-iNPH groups. This pilot study suggests the A/V ratio might be able to serve as a screening tool for iNPH. If so, this would be highly beneficial for patients and could have significant medical and socioeconomic implications.

Keywords: CSF; CSF DYNAMICS; DEMENTIA; GAIT.

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Conflict of interest statement

MJN has received funding from StatuManu ICP ApS for his PhD and undergraduate project and worked as a medical consultant for the company for 6 months. MCSA received partial funding from StatuManu ICP ApS for his PhD. NLE received funding from StatuManu ICP ApS for his undergraduate project.

Figures

Figure 1
Figure 1. Workflow for A/V ratio calculation from fundus videos. Key steps included frame selection, optic disc detection, quality assessment, vessel segmentation and alignment, measurement point localisation, vessel diameter measurement and final A/V ratio calculation. A/V, arteriole-venule.
Figure 2
Figure 2. Distribution of baseline A/V ratios from all 24 patients relative to ICP prior to infusion test and tap test for patients later diagnosed with iNPH or without iNPH (non-iNPH). A/V, arteriole-venule; ICP, intracranial pressure; iNPH, idiopathic normal pressure hydrocephalus.
Figure 3
Figure 3. Box plots showing the mean A/V ratio and mean ICP obtained prior to the initiation of the infusion test. A/V, arteriole-venule; ICP, intracranial pressure.
Figure 4
Figure 4. Receiver operating characteristic curve showing the ability of the A/V ratio to distinguish patients with iNPH from patients without iNPH. A/V, arteriole-venule; iNPH, idiopathic normal pressure hydrocephalus.
See this image and copyright information in PMC

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