[Comparison of long-latency reflex and mixed nerve silent period responses in various hypokinetic movement disorders].

Background and purpose: Long-latency reflex and mixed nerve silent period responses are electrophysiological methods to study the sensorimotor functions of the central nervous system. Here we aimed to study long-latency reflexes and mixed nerve silent period responses in different types of hypokinetic movement disorders in order to find an electrophysiological landmark to distinguish them.

Methods: We included 39 patients with idiopathic Parkinson's disease (IPD), 12 patients with multiple system atrophy (MSA), 10 patients with corticobasal syndrome (CBS), 5 patients with progressive supranuclear palsy (PSP) and 26 healthy participants. We recorded the segmental reflex, the long-latency reflexes and the mixed nerve silent period responses for each participant.

Results: C reflex, long-latency reflex-I and long-latency reflex-III responses were not obtained in any patients with PSP. Long-latency reflex amplitude/ F amplitude ratio was significantly lower in patients with IPD and PSP compared to healthy individuals (p=0.036, p=0.006 respectively). The mixed nerve silent period end latencies were significantly longer in IPD, MSA, CBS groups compared to the healthy individuals (p=0.026, p=0.050, p=0.008 respectively).

Conclusion: We suggest that recording long-latency reflex, particularly C reflex responses may provide promising results in distinction of CBS and MSA from PSP. Prospective studies with clinical findings and brainstem reflexes may offer more information.