# Hypometabolism and atrophy patterns associated with Niemann-Pick type C

## TL;DR

This study shows that [18F]FDG PET imaging can detect early brain changes in Niemann-Pick type C disease more effectively than MRI, aiding diagnosis and tracking progression.

## Contribution

The study identifies a distinct hypometabolism pattern in NP-C using [18F]FDG PET, suggesting its potential as a more sensitive diagnostic and monitoring tool.

## Key findings

- [18F]FDG PET showed higher sensitivity than MRI in detecting brain changes in NP-C patients.
- Cerebellar hypometabolism was strongly linked to ataxia and showed the most significant longitudinal decline.
- Miglustat treatment was associated with a trend of slower cerebellar hypometabolism progression.

## Abstract

Niemann–Pick disease type C (NP-C) is a rare genetic lysosomal lipid storage disorder characterized by progressive neurological impairment. Early diagnosis is critical for initiating treatment with miglustat, which can decelerate disease progression. In this study, we evaluated a cohort of 22 NP-C patients who underwent MRI, [18F]FDG PET, and clinical assessment at baseline. We performed a cross-sectional and longitudinal imaging study evaluating the role of [18F]FDG PET as an adjunct diagnostic tool for NP-C alongside MRI, the current neuroimaging standard.

Group-level MRI analysis identified significant cerebellar and thalamic atrophy (d = 1.56, p < 0.0001 and d = 1.09, p < 0.001, respectively), with less pronounced involvement of the frontal lobe and hippocampus, which aligned with existing neuropathological understanding and guidelines. Conversely, [18F]FDG PET imaging revealed extensive hypometabolism in the cerebellum, thalamus, and cingulate cortex (d = 1.42, p < 0.0001), and moderate hypometabolism in broad frontotemporal areas. [18F]FDG PET provided higher effect sizes across all brain regions, including regions without apparent atrophy, which suggests that it may be more sensitive than MRI for detecting NP-C neurodegenerative changes. Single-subject visual assessment of individual PET images further validated the clinical utility of [18F]FDG PET, with significant hypometabolism observed in the cerebellum, thalamus and anterior and posterior cingulate reported by physicians in 17/22 patients. Both hypometabolism and atrophy in the cerebellum were associated with ataxia, (more strongly indicated by [18F]FDG PET, p < 0.0001 vs. MRI, p = 0.07). Medial temporal lobe atrophy was associated with cognitive impairment (p < 0.05), and frontal hypometabolism was slightly related to behavioural impairment (p < 0.07). Longitudinal [18F]FDG PET analysis revealed progressive subcortical, cortical and cerebellar hypometabolism, which was most pronounced in the cerebellum (-12% per year, p < 0.001). Patients treated with miglustat showed a trend towards attenuated cerebellar hypometabolism progression compared to untreated patients (p = 0.10).

Our findings delineate a discernible hypometabolism pattern specific to NP-C that distinguishes it from other neurodegenerative conditions, thus suggesting that [18F]FDG PET might be a promising tool for NP-C diagnosis and to study disease progression.

XUNTA 2015/140. Registered 21 April 2015.

The online version contains supplementary material available at 10.1186/s13550-025-01208-8.