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A Silent Period of Levator Palpebrae Activity Induced By Median Nerve Stimulation

Author(s): Hilmi UYSAL | Ferah KIZILAY | Barın SELÇUK | Murat ERSÖZ | Müfit AKYÜZ

Journal: Journal of Neurological Sciences
ISSN 1300-1817

Volume: 27;
Issue: 1;
Start page: 28;
Date: 2010;
Original page

Keywords: Levator palpebrae | silent period | median nerve stimulation

Scientific Background: Levator palpebrae muscle is known to have a tonic activity which is inhibited in conditions where consciousness is lost. Therefore, there must be a direct relationship between ascending reticular activating system and nucleus of levator palpebrae in brainstem.Objectives: In this study, we have investigated electrophysiological clues related to this hypothesis. Material and Methods: We examined 6 patients with total peripheral-type facial palsy. A needle electromyogram electrode was used to record levator palpebrae muscle activity during median nerve stimulation. While the eyes were open, we stimulated the median nerve at the wrist with 0.5-1 msec. stimuli. We recorded the reflex activity of the levator palpebrae muscle.Results: We report that median stimulation produced a silent period with the duration of 25±4 msec. However, there was no similar silent period in the orbicularis oculi muscle with the stimulation of the median nerve in the normal side.Conclusions: This silent period may be an electrophysiological sign of the relationship between the ascending reticular activating system and the levator palpebrae muscle. Although this pattern was in fact an inhibitory type it could also be a polysynaptic reflex relationship of excitatory type since it leads to inhibition during sleep, as well.
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