Investigation On Parameters Of Vestibular-evoked Myogenic Potentials In Normal Volunteers Of Different Ages

Objective: We examined vestibular-evoked myogenic potential (VEMP) in different ages of healthy adult volunteers, to investigate the effects of age on the vestibular-evoked myogenic potential, and the relationship between the potentials and the amplitude in different ages and set up the range of normal values, then use it in clinic in the future. We chose some typical case to examine their VEMPs, and estimate the extent of disease and the prognosis.Methods: Sixty-seven healthy adult volunteers (37 male and 30 female) were investigated in this study. The subject age was distributed between 10 and 60 years old, the average was 30.184±13.886 years old. They all had never disease in both ears and vestibular system. They were divided in three groups according to their age, group 1:10~20 years old,23 volunteers; group 2:21~40 years old,24 volunteers; group 3:41~60 years old,20 volunteers; then examined their VEMPs, analyzed the parameters.EMG activity was recorded from the upper half of the SCM muscle using surface electrodes, with a reference electrode on the upper edge of the sternum and a ground electrode on the forehead. Care was taken to place the bilateral electrodes symmetrically. During each recording session, the subject raised the head 15~20cm away from the bed to keep the SCM muscle under tension. Rarefaction clicks of 0.1-millisecond duration were presented at a rate of 3.1 per second through a headphone. The EMG signal was amplified and band pass filtered (30 to 3000Hz) and it was averaged on computer using the SmartEP software package .The analysis window was 100 ms wide and the sampling rate was 500 Hz per second. The responses to 128 stimuli were averaged and repeated twice.Results:1. The range of normal values (ms): the right side: P13:12.045±1.360, N23 :19.466±2.209; the left side:P13:12.316±1.375,N23:19.354±2.158, IAD ( interaural amplitude difference): 0.162±0.146, the amplitude ratio: 0.986±0.324.2. No significant latencies differences among the three groups, No gender-related differences were detected in the VEMP. There was a significant correlation between age the p13n23 amplitude of the VEMP, it was negative correlation between age and the p13n23 amplitude, whereas no significant correlation was observed between age and left-right differences of the VEMP.Conclusions:1. We examined vestibular evoked myogenic potential (VEMP) in different ages of healthy adult volunteers, drew the conclusion that to keep the SCM muscle under tension during each recording session and the integrality of the vestibular neural pathways are necessary.2. No significant latencies difference among the three groups, No gender-related differences were detected in the VEMPs. The amplitude fluctuated greatly, but the IAD and the amplitude ratio are stabilization, which can use in clinical widely. There was a significant correlation between age the p13n23 amplitude of the VEMP, which was negative correlation between age and the p13n23 amplitude, whereas no significant correlation was observed between age and left-right differences of the VEMP. It is safe to evaluate the VEMP using the value of the non-affected side when assessing unilateral lesions. However, it may be necessary to take age into account in evaluating the VEMP when bilateral lesions are suspected.3. VEMP is an important method in clinical, which can detective the function of the sacculus and thalamencephalon, and the development of the vestibular system.