小脳橋角部腫瘍3症例におけるクリック音刺激による前庭性頸筋電位 Vestibular Evoked Myogenic Potentials in Three Patients with Cerebellopontine Angle Tumors
Vestibular evoked myogenic potentials (VEMPs) have been reported as a clinical test on the vestibular system. We examined VEMPs in three patients with cerebel-lopontine angle tumors (CPAT) and in six normal subjects. To record VEMPs, a positive electrode was placed on the sternocleidomastoid muscle (SCM), and a reference electrode was placed on the lateral end of the upper sternum. During the recording, subjects were instructed to rotate their heads in the direction opposite to the stimulated side to activate the SCM. Electromyographic signals from each side were amplified and bandpass filtered (20-2000 Hz). Clicks (0.1 ms, 95 dBnHL) were presented through a headphone. The stimulation rate was 5 Hz, the analysis time was 50 ms. The responses to 200 stimuli were averaged. The patients with CPAT also underwent pure tone audiometry (PTA), ABR, and caloric tests. In all normal subjects, VEMPs, a positive peak at about 13 ms and a negative peak at about 23 ms after presentation of click were recorded on the SCM ipsilateral to the stimulated side. All patients with CPAT showed abnormal VEMPs on the affected side. Two patients showed absence of VEMPs although caloric responses were present. One patient showed decreased VEMPs, but his caloric responses were normal. VEMPs in this patient disappeared after neurosurgery, although pure tone hearing and ABRs were not changed. Results of our study and a review of the literature suggested that VEMPs could reflect a function different from those of ABRs and caloric responses.
- Equilibrium research
Equilibrium research 56(5), 454-459, 1997-10-01