Vestibulo masseteric reflex and acoustic masseteric Reflex. Normative data and effects of age and gender

To provide normative data for the Vestibulo-Masseteric Reflex (VMR) and Acoustic-Masseteric Reflex (AMR) in healthy subjects, stratified for age and gender.

A total of 82 healthy subjects (M:F 43:39, mean age 39.3 ± 18.4 years, range 13-79 years) underwent recording of click-evoked VMR and AMR (0.1 ms duration, 5 Hz frequency) from active masseter muscles. Masseter responses to uni- and bilateral stimulation were recorded in a zygomatic and a mandibular configuration, according to the position of the reference electrode. Stimulation intensity curves were recorded for each reflex in ten subjects (mean age 20.7 ± 8.1 years). Gender effect was investigated in 62 subjects and age effect was analyzed in six 10-subject groups aged from <25 to >65 years. Onset and peak latencies, interpeak intervals, raw and corrected amplitudes, latency and amplitude asymmetries were analyzed.

VMR had a higher elicitation rate than AMR. For both reflexes, rates of elicitation, and corrected amplitudes were higher in the zygomatic configuration, and bilateral stimulation elicited larger responses. Best acoustic ranges of elicitation were 98-113 dB for AMR and 128-138 dB for VMR. Reflex latencies were shorter in females than males. Frequency and amplitude of VMR and AMR decreased substantially over 55 year olds.

VMR and AMR can be easily performed in any clinical neurophysiology laboratory.

These reflexes can find application in the investigation of brainstem function in central neurological disorders.