The role of cochlear and vestibular afferents in long-latency cervical vestibular evoked myogenic potentials.

ABSTRACT

OBJECTIVE: To examine the origin of cervical vestibular evoked myogenic potential (cVEMP) late waves (n34-p44) elicited with air-conducted click stimuli. DESIGN: Using a retrospective design, cVEMPs from normal volunteers were compared to those obtained from patients with vestibular and auditory pathologies. STUDY SAMPLE (1) Normal volunteers (n = 56); (2) severe-to-profound sensorineural hearing loss (SNHL) with normal vestibular function (n = 21); (3) peripheral vestibular impairment with preserved hearing (n = 16); (4) total vestibulocochlear deficit (n = 23). RESULTS: All normal volunteers had ipsilateral-dominant early p13-n23 peaks. Late peaks were present bilaterally in 78%. The p13-n23 response was present in all patients with SNHL but normal vestibular function, and 43% had late waves. Statistical comparison of these patients to a subset of age-matched controls showed no significant difference in the frequencies, amplitudes or latencies of their ipsilateral early and late peaks. cVEMPs were absent in all patients with vestibular impairment. CONCLUSION: The presence of long-latency cVEMP waves was not dependent on the integrity of sensorineural hearing pathways, but instead correlated with intact vestibular function. This finding conflicts with the view that these late waves are cochlear in origin, and suggests that vestibular afferents may assume a more prominent role in their generation.