Normalization reduces intersubject variability in cervical vestibular evoked myogenic potentials.
OBJECTIVE
Cervical vestibular evoked myogenic potentials are used to assess saccular and inferior vestibular nerve function. Normalization of the VEMP waveform has been proposed to reduce the variability in vestibular evoked myogenic potentials by correcting for muscle activation. In this study, we test the hypothesis that normalization of the raw cervical VEMP waveform causes a significant decrease in the intersubject variability.


METHODS
Prospective cohort study.


METHODS
Large specialty hospital, department of otolaryngology.


METHODS
Twenty healthy subjects were used in this study.


METHODS
All subjects underwent cervical vestibular evoked myogenic potential testing using short tone bursts at 250, 500, 750, and 1,000 Hz. Both intersubject and intrasubject variability was assessed.


METHODS
Variability between raw and normalized peak-to-peak amplitudes was compared using the coefficient of variation. Intrasubject variability was assessed using the intraclass correlation coefficient and interaural asymmetry ratio.


RESULTS
cVEMPs were present in most ears. Highest peak-to-peak amplitudes were recorded at 750 Hz. Normalization did not alter cVEMP tuning characteristics. Normalization of the cVEMP response caused a significant reduction in intersubject variability of the peak-to-peak amplitude. No significant change was seen in the intrasubject variability.


CONCLUSIONS
Normalization significantly reduces cVEMP intersubject variability in healthy subjects without altering cVEMP characteristics. By reducing cVEMP amplitude variation due to nonsaccular, muscle-related factors, cVEMP normalization is expected to improve the ability to distinguish between healthy and pathologic responses in the clinical application of cVEMP testing.
*Department of Otolaryngology, Massachusetts Eye and Ear Infirmary; †Department of Otology and Laryngology, Harvard Medical School; ‡Department of Audiology, Massachusetts Eye and Ear Infirmary; and §Eaton Peabody Lab, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, U.S.A.
Mark J
MJ
van Tilburg
Barbara S
BS
Herrmann
John J
JJ
Guinan
Steven D
SD
Rauch
D015331:Cohort Studies; D006801:Humans; D010036:Otolaryngology / Q000379:methods*; D011446:Prospective Studies; D058585:Vestibular Evoked Myogenic Potentials / Q000502:physiology*; D014725:Vestibular Nerve / Q000502:physiology*