Short latency afferent inhibition in Parkinson's disease patients with dementia

Background: Cortical cholinergic deficiency occurs in Parkinson's disease (PD) and is more severe in PD dementia (PDD). Short-latency afferent inhibition (SAI) can be used as an in vivo test for the evaluation of the cholinergic circuit in the cerebral motor cortex. Methods: SAI and neuropsychological profile were studied in nondemented PD, PDD, Alzheimer's disease (AD) patients, and age-matched controls. Results: SAI was significantly impaired in AD cases (94.7 +/- 6.2 versus 55.5 +/- 4.0; P < 0.0001). In PD patients, it was not different from controls (61.4 +/- 5.8 versus 55.5 +/- 4.0; P = 0.412). PDD cases demonstrated a significant impairment in SAI (91.4 +/- 5.2 versus 55.5 +/- 4.0; P < 0.0001). A high correlation was found between SAI and MiniMental State Examination (r = -0.68; P < 0.0001). Conclusions: These findings add further evidence that differential cholinergic deficiency occurs in PD and PDD. SAI can be a neurophysiological correlate of PDD. (c) 2012 Movement Disorder Society