Sensorimotor gating deficits in multiple system atrophy: comparison with Parkinson's disease and idiopathic REM sleep behavior disorder.

Background: Prepulse inhibition (PPI) of the auditory blink reflex is a measure of sensorimotor gating, which reflects an organism's ability to filter out irrelevant sensory information. PPI has never been studied in patients with multiple system atrophy (MSA), although sensorimotor deficits are frequently associated with synucleinopathies. We investigated whether alterations in PPI were more pronounced in MSA compared with Parkinson's disease (PD), idiopathic rapid eye movement sleep behavior disorder (iRBD) and healthy controls.

Methods: 10 patients with MSA, 12 patients with iRBD, 40 patients with PD, and 20 healthy controls completed the study. A passive acoustic prepulse inhibition paradigm was applied with prepulses 5 dB and 15 dB above background noise at 30-, 60-, 120- and 300-ms intervals.

Results: Non-parametric analyses showed that MSA patients had significantly lower prepulse inhibition, as measured with max-amplitude, than PD patients and iRBD patients on the 60 ms-85 dB and 120 ms-85 dB inter-stimulus intervals. The same relation was found when using area under the curve. No differences were found between groups for the 30 ms-85 dB and 300 ms-85 dB. Furthermore, blink reflex characteristics such as habituation did not differ between patients and controls.

Conclusions: The present study showed that sensorimotor gating, as measured with PPI, is markedly reduced in MSA. This may be due to the pronounced severity of striatal and brainstem dysfunction, as well as the degeneration of other structures related to the PPI modulating pathways in MSA. PPI may be a non-invasive neurophysiological measure that can aid in the differential diagnosis between PD and MSA.