Cognitive profiling in relation to short latency afferent inhibition of frontal cortex in multiple system atrophy

Cognitive dysfunction occurs in multiple system atrophy (MSA) more frequently than previously known. As a type of synucleinopathy, pathology spreads widely in cortical and subcortical areas as the disease advances. The exact anatomical and imaging substrates, and electrophysiological or biochemical indicators of cognitive impairment in MSA are not yet clear. Diminished short-latency afferent inhibition (SAI) of motor cortex was shown to be an electrophysiological correlate of dementia and mild cognitive impairment associated to Parkinson's disease (PD). We hypothesize that it can also be electrophysiological correlate of cognitive impairment in MSA.

We studied SAI and a neuropsychological test battery in 19 non-demented MSA patients (11 MSA-P and 8 MSA-C), 10 non-demented PD patients and 10 healthy controls. Neuropsychological test scores were grouped in four main cognitive domains (attention, memory, executive and visuo-spatial functions) and were analyzed by factor analysis.

All subject groups were matched for age. Moreover, the MSA-P, MSA-C, and PD groups were matched for disease duration. Scores of cognitive domains were similar in MSA and PD cases, while scores in attention, executive and visuo-spatial domains were worse in MSA than controls (p < 0.05). SAI was normal in PD but decreased in MSA patients by reaching statistical significance in MSA-C subtype. SAI response was correlated with cognitive performances measured by factor scores of neuropsychological test battery in all study subjects.

These results show that cognitive functions are impaired in MSA patients compared to controls as well as a parallel reduction in SAI response.