Neuronal Loss in the Substantia Nigra and Ventral Tegmental Area in Parkinson’s Disease and Alzheimer’s Disease
Regional neuronal loss in the substantia nigra (SN) and ventral tegmental area (VTA) was studied in relation to extrapyramidal symptoms and dementia in patients with Alzheimer’s disease (AD) and Parkinson’s disease (PD) and controls. The number of neurons in the substantia nigra was reduced both in AD and PD, although to a greater degree in the latter. In the VTA, reduction in neuronal counts was seen only in PD but not in AD. Nigral degeneration was related to extrapyramidal symptoms in both AD and PD. Interestingly, dementia was associated with neuronal loss in the medial SN in PD but not in AD. The results suggest that nigral degeneration may contribute as a subcortical component to the intellectual impairment in patients with PD but not in AD implicating the possibility of different pathophysiological bases of cognitive impairment in these diseases.
KeywordsSubstantia Nigra Ventral Tegmental Area Extrapyramidal Symptom Neuronal Count Orofacial Dyskinesia
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