Effect of reading on surface electromyogram recordings in patients with blepharospasm.
PURPOSE: To compare the surface electromyogram recordings between patients with benign essential blepharospasm and controls while maintaining primary gaze and reading in downgaze. METHODS: A university-based, prospective case series of 7 benign essential blepharospasm patients and 7 normal patients. Bilateral lower eyelid preseptal orbicularis oculi muscle potentials were recorded via surface electromyogram and video while performing a standardized 60-second task that was divided in 3 equal 20-second subtasks. Specifically, patients were asked to maintain primary gaze for the first 20-second interval, to read quietly for the second interval, and again maintain primary gaze for the third 20-second interval. Fourteen trials capturing bilateral recordings were performed in each group; qualitative and quantitative analysis of the surface electromyogram recordings was performed and compared both between patient groups and between subtasks. Blepharospasm patients were also asked to describe the effect of reading on their spasms. Specifically, they were asked before the study if reading lessened or worsened their spasms and then were asked poststudy if their symptoms lessened or worsened during the reading task. RESULTS: The mean surface electromyogram potential of the orbicularis muscle was significantly less in normal eyes when compared with blepharospasm eyes for each task. Furthermore, the mean surface electromyogram potential during the reading task was significantly reduced when compared with the primary gaze task in all eyes. Only blepharospasm patients noticed this reduction subjectively. CONCLUSIONS: Although conventional wisdom regarding blepharospasm suggests that reading is an exacerbating factor, short durations of reading seem to relieve spasms. This may be due to the effect of downgaze on the blink reflex and may offer possible areas of investigation for novel blepharospasm treatments.
Richard, MJ; Woodward, DJ; McCoy, AN; Woodward, JA
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