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 Mini-Mental 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.