Comparison of the Blink Reflex and R۲ Recovery Cycle Parameters Between Blepharospasm and Healthy Subjects

 Background & Objective:  The blink reflex recovery cycle indicates the excitability of interneurons in the brainstem. In this study, we aimed to investigate the blink reflex and R۲ recovery cycle in patients with benign essential blepharospasm (BEB).  Materials & Methods:  This prospective case-control study compared the blink reflex and R۲ recovery in ۱۸ BEB patients with ۱۸ age- and gender-matched healthy individuals. The blink reflex was measured in a stimulation duration of ۰.۲ ms, and R۱, R۲, and R۲’ were recorded for all subjects. The R۲ recovery cycle was measured by stimulation of the supraorbital nerve at four interstimulus intervals (ISI) of ۲۰۰, ۳۰۰, ۵۰۰, and ۱۰۰۰ ms, with the same intensity as the previous test. The R۲ recovery index was calculated and compared with the control group via independent sample t-test. Two-tailed P-value less than ۰.۰۵ was considered statistically significant.  Results:  The blink reflex (R۱, R۲, and R۲’ responses) distal latencies and amplitudes in the BEB group were not significantly different from the control group (P>۰.۰۵). The R۲ recovery index in all intervals was significantly higher in the BEB group than the control group (P=۰.۰۰). The most significant difference between the BEB and control groups regarding the R۲ recovery indices was observed at ISIs of ۳۰۰ and ۲۰۰ ms (۸۰.۳۶ vs. ۱۶.۹۹ and ۷۵.۷۰ vs. ۱۲.۵۷, respectively). There was a negative correlation between the patient’s age at the onset of disease and the R۲ recovery index; however, it was not statistically significant (P>۰.۰۵).  Conclusion:  Our findings showed that the R۲ recovery reflex was higher in BEB patients than the normal population. Therefore, it can be a helpful index for differentiating BEB cases from psychogenic or malingering ones.

Keywords:

Blepharospasm , Blink reflex , R۲ recovery cycle