Somatosensory and auditory startle reaction in patients with movement disorders

Publication date: March 2016
Source:Clinical Neurophysiology, Volume 127, Issue 3
Author(s): A. Gunduz, M.E. Kiziltan, G. Kiziltan, D. Yavuz, D. Karadeniz
BackgroundStartle reflex (SR) is a generalized defense reaction which is elicited by unexpected stimuli. To elicit SR, auditory and electrical stimulations are used in electrophysiological investigations. Somatosensory startle reflex (SS-SR) is recently described in healthy volunteers after median and tibial stimulation. Studies in patients with brainstem lesions showed importance of upper brainstem in development of SS-SR. Here, we aim to investigate SS-SR systematically in various movement disorders to address its characteristics in comparison to ASR.MethodsWe have examined ASR and SS-SR in patients with dystonia (n=12), multiple system atrophy (n=8), corticobasal degeneration (n=5), restless legs syndrome (n=14), progressive supranuclear palsy (n=11), essential tremor (n=18) and idiopathic PD (n=16) and healthy volunteers (n=35) under the same conditions. ASR and SS-SR were recorded over orbicularis oculi (o.oc), sternocleidomastoid (SCM), and biceps brachii (BB) after bilateral auditory and median nerve electrical stimulations, respectively.ResultsThe pattern and probability rates over each three muscle of ASR were similar in MSA, RLS, ET, PD and healthy individuals. Probability rates of responses over each muscle and total ASR probability were the highest in dystonia group whereas they were the lowest in CBD and PSP (po.oc=0.016, pscm=0.036, pbb=0.000, ptotal=0.009). Onset latencies of O.oc responses were also longer in CBD and PSP groups (p=0.001). Presence of SSR was also the highest in dystonia and lowest in PSP group similar to ASR. Latency of O.oc response was longest in CBD group. Pattern of SS-SR was similar to healthy individuals in all disease groups except dystonia and MSA in which BB responses were more common than SCM responses.ConclusionsThe findings of ASR parallel the previous findings. Dystonia patients are known to have exaggerated ASRs. The decreased response in PSP was previously suggested as a support to show extent of pathology. Findings regarding SS-SR also parallel ASR. SS-SR is also exaggerated in dystonia. Different pattern of response appears to be a reflection of overflow phenomenon. However, development of withdrawal reaction is a possibility. Shorter onset latencies in dystonia group probably also reflect increased excitability. Absence of SS-SR or longer latencies in PSP reflects impairment of its pathway which supports the opinion that it may share pathway with ASR and its generator is possibly in the upper brainstem.



from Physiology via xlomafota13 on Inoreader http://ift.tt/1PPwiso
via IFTTT