S M Rosengren1, N P McAngus Todd, J G Colebatch. 1. Institute of Neurological Sciences and UNSW Clinical School, Prince of Wales Hospital Randwick, Sydney, NSW 2031, Australia.
Abstract
OBJECTIVE: To investigate the origin, whether ocular or extraocular, of the short latency frontal potential (N15) reported by following vestibular stimulation. METHODS: Fourteen subjects with low VEMP thresholds (V(T)) and 9 patients with vestibular or ocular disorders were stimulated at the mastoid with bone-conducted tone bursts (500 Hz, 8 ms) above vestibular threshold, using a B71 bone vibrator. Surface potentials were recorded from Fpz and around the eyes and referred to linked earlobes. RESULTS: The N15 was present at Fpz, but was largest around the eyes (mean amplitude 2.6 microV, peak latency 13.4 ms, with stimulation at +18 dB above threshold) and was generally in phase above and below the eyes. The response was vestibular-dependent and modulated by alteration of gaze direction. The potentials were delayed in a patient with Miller Fisher syndrome and were larger in patients with superior canal dehiscence than in controls. CONCLUSIONS: We report a new vestibular-evoked extraocular potential. Its properties are not consistent with an eye movement. It is likely to be produced, mainly or exclusively, by synchronous activity in extraocular muscles (i.e. a myogenic potential). SIGNIFICANCE: Vestibular-evoked extraocular potentials extend the range of vestibular pathways that can be assessed electrophysiologically, and may be a useful additional test of vestibular function.
OBJECTIVE: To investigate the origin, whether ocular or extraocular, of the short latency frontal potential (N15) reported by following vestibular stimulation. METHODS: Fourteen subjects with low VEMP thresholds (V(T)) and 9 patients with vestibular or ocular disorders were stimulated at the mastoid with bone-conducted tone bursts (500 Hz, 8 ms) above vestibular threshold, using a B71 bone vibrator. Surface potentials were recorded from Fpz and around the eyes and referred to linked earlobes. RESULTS: The N15 was present at Fpz, but was largest around the eyes (mean amplitude 2.6 microV, peak latency 13.4 ms, with stimulation at +18 dB above threshold) and was generally in phase above and below the eyes. The response was vestibular-dependent and modulated by alteration of gaze direction. The potentials were delayed in a patient with Miller Fisher syndrome and were larger in patients with superior canal dehiscence than in controls. CONCLUSIONS: We report a new vestibular-evoked extraocular potential. Its properties are not consistent with an eye movement. It is likely to be produced, mainly or exclusively, by synchronous activity in extraocular muscles (i.e. a myogenic potential). SIGNIFICANCE: Vestibular-evoked extraocular potentials extend the range of vestibular pathways that can be assessed electrophysiologically, and may be a useful additional test of vestibular function.
Authors: Sendhil Govender; Sally M Rosengren; Danielle L Dennis; Louis J Z Lim; James G Colebatch Journal: Exp Brain Res Date: 2015-09-24 Impact factor: 1.972
Authors: Miriam S Welgampola; Americo A Migliaccio; Oluwaseun A Myrie; Lloyd B Minor; John P Carey Journal: Clin Neurophysiol Date: 2008-12-12 Impact factor: 3.708