The effect of rise/fall time on vestibular-evoked myogenic potential triggered by short tone bursts.

Vestibular-evoked myogenic potentials (VEMPs) are used more and more frequently as a clinical tool to test if the sacculocollic reflexes are intact in patients. They can be evoked by short tone bursts (STBs) as well as by clicks. Although most previous studies used traditional clicks to generate VEMP responses, our clinical experience showed that STBs were prone to evoke them more clearly, at least in some patients. Four kinds of STB stimulation patterns in a random order were used to test 22 ears using changing rise/fall times (0.3, 1, 3 and 10 ms). VEMP responses (p13/n23) triggered by these patterns were clearly observed in all 22 ears. When the rise/fall time was prolonged from 0.3 to 10 ms, the p13 latency was prolonged in parallel. There was a similar trend for the n23 latency, although a significant difference was not attained between 0.3 ms and 1 ms rise/fall times. Considering the p13 and n23 latencies for the 4 rise/fall times, the variances were smallest for the 1 ms stimulation, meaning that it caused the smallest interaural latency differences. The amplitude or relative amplitude in the individual ears tested was lowest for the 10 ms stimulation, being comparable among the other 3 rise/fall times. In conclusion, the 1 ms rise/fall time was a remarkable stimulation pattern because its VEMP responses were simultaneously more constant and conspicuous.