# Regional White Matter Lesion Load in Elderly Patients With Somatic vs. Non‐Somatic Delusional Disorder

## TL;DR

This study compares brain white matter damage in elderly patients with somatic versus non-somatic delusions, finding distinct patterns linked to different types of delusional content.

## Contribution

The study identifies specific regional white matter lesion load differences between somatic and non-somatic delusional disorder subtypes in elderly patients.

## Key findings

- Both somatic and non-somatic delusional patients showed increased white matter lesions in the anterior cingulate and lateral prefrontal regions.
- Somatic delusional patients had higher white matter lesions in sensorimotor areas of the frontal lobe compared to non-somatic patients and healthy controls.
- The findings support a neuromechanistic model linking somatic delusions to internal bodily focus and non-somatic delusions to external cognitive distortions.

## Abstract

Delusional disorders (DD) are among the most debilitating mental disorders in the elderly. Persistent monothematic delusions frequently include paranoid and persecutory beliefs, as well as various forms of somatic delusions, including delusions of being infested by pathogens. So far, little is known about the neural correlates of DD. Yet, particularly in elderly patients, white‐matter lesions (WML) are thought to play an important pathophysiological role.

To investigate regional WML in patients with DD, structural MRI was used, followed by automated lesion segmentation methods to facilitate WML load (WMLL) comparisons between healthy controls (HC, n = 28) and patients with distinct types of DD, that is, somatic (n = 16) versus non‐somatic DD (n = 17). Patients with somatic DD presented with specific delusional content, that is, beliefs of delusional infestation (DI), whereas individuals with non‐somatic DD (non‐DI) showed predominantly paranoid and persecutory content.

Regions with higher WMLL in both DI and non‐DI patients compared to HC included the anterior cingulate and lateral prefrontal regions located in the middle frontal gyrus. Regions with higher WMLL in DI patients versus both HC and non‐DI patients were predominantly located in the sensorimotor areas of the frontal lobe.

The data suggest distinct patterns of regional WMLL in elderly patients with DI versus non‐DI. The anatomical distribution of WMLL supports a neuromechanistic model that emphasises the importance of brain areas that drive the internal bodily focus of somatic delusions versus the externalised cognitive distortions that can be observed in non‐somatic delusions.