Gray Matter Volume Is Altered in Idiopathic REM Sleep Behavior Disorder

Idiopathic rapid eye movement sleep behavior disorder (iRBD) is associated with widespread gray matter volume (GMV) alterations, which may underlie the cognitive and sensorimotor impairment observed in the disorder. These study findings were published in Sleep Medicine.

In iRBD, patients present with abnormal behavior and a loss of muscle atonia in rapid eye movement (REM) sleep. Further, the vast majority of patients with iRBD eventually develop Parkinson disease, dementia with Lewy bodies, and/or multiple system atrophy – making iRBD a prodromal marker of α-synucleinopathies. Previous studies that have explored the brain structural changes and neuroanatomical correlates of this disorder have produced mixed findings.

Therefore, to gain a comprehensive understanding of the potential gray matter alterations associated with iRBD, investigators from Sichuan University in China conducted a systematic review and meta-analysis. The investigators searched publication databases through July 2024 for whole-brain voxel-based morphometry studies reporting GMV in iRBD and healthy controls.

A total of 11 studies comprising 12 unique datasets were included in this analysis. The studies were published between 2012 and 2024. The pooled study population comprised data from 341 patients with iRBD and 288 healthy controls. The reported mean age at iRBD onset ranged between 53.2 and 62 years and the duration of iRBD was between 5.93 and 12.1 years.

The patients with iRBD had significantly decreased GMV in the right temporal pole and inferior temporal gyrus, bilateral gyri rectus, medial orbital parts of the bilateral superior frontal gyri, right caudate nucleus, and right olfactory cortex relative to controls. Conversely, GMVs were increased in iRBD in bilateral cerebellar lobules 8 and 9, bilateral thalamus, right cerebellar crus 1 and 2, and left superior occipital gyrus relative to controls.

These results were consistent in the sensitivity analyses that used jackknifing. Further, the results of a subgroup analysis indicated that antidepressant use did not affect these general trends.

Reductions in GMV of the bilateral gyri rectus was associated with older age, decreases in GMV in the right temporal pole was negatively associated with disease duration and positively related with age at onset, and increases in GMV of the bilateral thalamus and bilateral cerebellar lobule 9 were associated with increased Unified Parkinson’s Disease Rating Scale Part III (UPDRS III) scores.

“Patients with iRBD showed decreased GMV in the bilateral prefrontal cortices and gyrus rectus, right temporal lobe, and right caudate, while increased GMV in the bilateral cerebellum and thalamus,” the investigators concluded. “These changes give us a description of neural alterations in iRBD, and may enhance our understanding of the early signs of neurodegeneration in the prodromal stage of α-synucleinopathies.”

The primary study limitation is the use of pooled peak coordinates instead of raw data when performing the meta-analysis.

This article originally appeared on Sleep Wake Advisor