Visual hallucinations in Parkinson's disease: The critical role of intermediate nucleus basalis of Meynert.

BACKGROUND AND OBJECTIVE

Patients with Parkinson's disease (PD) often experience visual hallucinations (VH) and delusions. PD patients with VH reportedly have a higher incidence of dementia than PD patients without VH. The nucleus basalis of Meynert (nbM) comprises acetylcholine-releasing neurons that are critical for memory, attention, and arousal. Notably, the nbM also exhibits pathological α-synuclein accumulation, which is a hallmark of Lewy body diseases, including PD. In the present study, we investigated the distribution of abnormal α-synuclein accumulation in the nbM.

METHODS

nbM sections of PD 28 autopsy patients were prepared and analyzed via immunohistochemistry using antibodies against phosphorylated α-synuclein and Choline acetyltransferase. The analysis included quantitative assessments of Choline acetyltransferase or α-synuclein positive neurons.

RESULTS

Immunohistochemical analyses of the nbM sections revealed significant cholinergic neuron loss in the intermediate nbM of patients with VH compared with those without VH (137 vs. 191, p = 0.04). Moreover, the ratio of α-synuclein-positive cells to choline acetyltransferase-positive cells was significantly higher in patients with VH than in those without VH (p = 0.03).

CONCLUSIONS

Pathological changes in nbM-particularly cholinergic deficits in the intermediate part-were therefore identified as potential contributors to VH in PD. These findings add to our understanding of the neuropathological basis of VH in PD and may inform future therapeutic strategies.