The effect of paired stimuli on blink reflex latencies in normal subjects

Introduction: In this study we assessed the effect of paired stimuli on the latencies and amplitudes of the blink reflex. Methods: Blink reflexes were performed with single and paired (5-ms interstimulus interval) stimuli in 47 patients. The changes in latencies between paired and single stimuli were calculated. Results: Paired stimulation produced two types of R1 waveform morphologies: single- and double-peaked waveforms. Increases in R1 and contralateral R2 latencies with paired stimulation were significantly higher in those with singlepeaked R1 responses compared to those with double-peaked R1 responses. Conclusions: Interpreting the blink reflex latencies using paired stimulation requires visualization of the R1 waveform morphology. A double-peaked R1 response requires no change in normal latency values, but the latency of a singlepeaked R1 should be interpreted from the second shock artifact. The effect on the R2 latency is variable