Vestibular evoked myogenic potentials in acute acoustic trauma

Abstract

Objectives: Anatomical proximity of the saccule to the stapedial footplate points to the possibility of acoustic trauma associated with saccular dysfunction. Therefore, it was the authors' premise that abnormal vestibular evoked myogenic potential (VEMP) after acute acoustic trauma may be caused by saccular damage from very high intensity noise; consequently, irreversible hearing loss ensued. The aim of this study was to investigate the VEMP responses in those with acute acoustic trauma.

Study design: A prospective study.

Setting: University hospital.

Patients: Twenty patients (29 ears) without previous ear disorders diagnosed as acute acoustic trauma were enrolled in this study.

Main outcome measures: Before treatment, each patient underwent pure tone audiometry and caloric and VEMP tests. Correlations between the hearing outcome and mean hearing level, sources of noise, caloric responses, or VEMP results were investigated.

Results: After 3 months of medication, complete recovery was achieved in 4 ears and hearing improvement in 4 ears, whereas hearing in 21 ears (72%) remained unchanged. Eighteen ears presenting normal VEMPs revealed hearing improvement in eight ears (44%) and unchanged hearing in ten ears (56%). However, hearing loss remained unchanged in all 11 ears (100%) with absent or delayed VEMPs, exhibiting a significant relationship between VEMP results and hearing outcome. Thus, VEMP test can predict the hearing outcome after acute acoustic trauma with a sensitivity of 44% and a specificity of 100%.

Conclusion: The greater the noise intensity, the severer damage on the cochlea and saccule is shown. Absent or delayed VEMPs in ears after acute acoustic trauma may indicate poor prognosis with respect to hearing improvement, whereas normal VEMP is not a powerful indicator for expectation of hearing improvement.