Cholinergic Basal Forebrain Degeneration in Isolated REM Sleep Behavior Disorder

Overview

This study demonstrates significant degeneration of the cholinergic nucleus basalis of Meynert (Ch4) in patients with isolated REM sleep behavior disorder (iRBD), a prodromal phase of Lewy body disorders. Ch4 atrophy correlates with limbic and neocortical structural changes and is linked to motor and cognitive symptom progression, highlighting distinct cholinergic and monoaminergic degeneration patterns in prodromal Lewy body disorders.

Background

Lewy body disorders (LBDs), including Parkinson’s disease (PD) and dementia with Lewy bodies (DLB), are characterized by α-synuclein pathology affecting multiple neurotransmitter systems. The basal forebrain cholinergic complex, particularly the nucleus basalis of Meynert (Ch4), provides cortical cholinergic innervation and is implicated in cognitive and motor symptoms in LBD. Isolated REM sleep behavior disorder (iRBD) is a robust prodromal marker of LBD, offering a unique window to study early cholinergic degeneration and its clinical impact. Prior studies suggested Ch4 volume reduction in iRBD but lacked large sample validation and comprehensive multimodal imaging analyses.

Data Highlights

Key Findings

• Ch4 volumes were significantly reduced in iRBD patients compared to healthy controls, whereas Ch1–3 volumes were not.
• Ch4 atrophy correlated positively with limbic regions (amygdala, cingulate cortex) and neocortical areas (frontal and temporal cortices).
• Both Ch1–3 and Ch4 volume reductions were modestly associated with more severe axial motor symptoms.
• Ch1–3 volume reduction predicted higher incidence of dementia and faster memory decline, while Ch4 reduction was linked to faster progression of limb bradykinesia.
• iRBD patients converting to PD showed predominant monoaminergic deficits with variable cholinergic involvement; those converting to DLB exhibited predominant cholinergic deficits with variable monoaminergic involvement.

Clinical Implications

Early detection of Ch4 degeneration in iRBD patients may help identify individuals at higher risk for cognitive decline and motor symptom progression. Differentiating cholinergic versus monoaminergic involvement could guide personalized therapeutic strategies targeting neurotransmitter systems in prodromal Lewy body disorders. Monitoring basal forebrain atrophy alongside clinical assessments may improve prognostication and management.

Conclusion

Cholinergic basal forebrain degeneration, particularly of Ch4, is a key pathological feature in the prodromal phase of Lewy body disorders, associated with distinct brain structural changes and clinical outcomes. These findings enhance understanding of neurodegenerative progression and may inform early intervention strategies.

References

1. Study Authors/Year -- Degeneration of Cholinergic Neurons in the Basal Forebrain Associated with Isolated REM Sleep Behavior Disorder