Researchers of this autopsy study tested whether degeneration of the nucleus basalis of Meynert (nbM)—the brain’s major cortical cholinergic source—differs between patients with Parkinson’s disease (PD) with versus without visual hallucinations (VH). Using nbM tissue from 28 PD donors, investigators performed immunohistochemistry for choline acetyltransferase (ChAT) to quantify cholinergic neurons and phosphorylated α-synuclein to index Lewy pathology, with counts taken across nbM subregions and compared by hallucination status. The rationale was that nbM projections modulate attention, arousal, and visual processing, functions implicated in PD hallucinations.
Patients with VH showed a selective cholinergic deficit in the intermediate nbM, with fewer ChAT-positive neurons than non-hallucinators (137 vs 191; p=0.04) and a higher ratio of α-synuclein–positive to ChAT-positive cells (p=0.03). These findings point to targeted nbM involvement—and associated cholinergic dysfunction—as a neuropathological substrate for VH in PD, complementing network-level accounts of impaired attentional gating. Clinically, they reinforce the rationale for cholinergic-based strategies to alleviate visual symptoms and motivate in-vivo studies (eg, basal forebrain imaging) that relate nbM integrity to hallucination severity over time. Limitations include the modest sample size and limited phenotyping of VH, underscoring the need for prospective, multimodal confirmation.
Reference: Hatsuta H, Mizutani M, Yagita K, Sano T, Takao M. Visual hallucinations in Parkinson’s disease: The critical role of intermediate nucleus basalis of Meynert. Parkinsonism Relat Disord. 2025;137:107935. doi: 10.1016/j.parkreldis.2025.107935.
Link: https://www.prd-journal.com/article/S1353-8020(25)00676-5/fulltext
