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Wei-Chung Hsu, MD, PhD; Jung-Der Wang, MD, PhD; June-Horng Lue, PhD; An-Shiou Day, MD; Yi-Ho Young, MD

Arch Otolaryngol Head Neck Surg. 2008;134(10):1099-1106.

Objective  To investigate whether the saccule exhibits temporary or permanent functional loss resembling threshold shifts in auditory brainstem response (ABR) of guinea pigs following noise exposure.

Design  Randomly bred guinea pigs were divided into 3 groups: A (short-term noise exposure, 30 minutes, n = 15), B (long-term noise exposure, 40 hours, n = 9), and C (no noise exposure, n = 5).

Setting  University hospital.

Main Outcome Measures  All animals underwent vestibular-evoked myogenic potential (VEMP) and ABR tests. Chronological changes of VEMP and ABR responses following noise exposure were analyzed and compared. After audiovestibular function testing, animals were killed for morphological study with light and electron microscopy.

Results  In group A, temporary VEMP loss and ABR threshold shifts recovered 2 and 4 days, respectively, after short-term noise exposure, with an interval of 2 days earlier in the recovery of VEMPs than that of ABR thresholds. In contrast, in group B, 78% and 83% of the ears exhibited permanent VEMP loss and ABR threshold shifts, respectively, 10 days following long-term noise exposure. In group C, all animals showed normal VEMPs and ABRs throughout the study period. Light and electron microscopic studies confirmed that loss of VEMPs correlated with saccular lesion.

Conclusions  The saccule can exhibit temporary or permanent functional loss resembling hearing threshold shifts in guinea pigs following noise exposure. Recovery of VEMP precedes restoration of hearing threshold after damage from short-term noise exposure. Conversely, permanent VEMP loss after long-term noise exposure may reflect permanent hearing threshold shifts.

Author Affiliations: Department of Otolaryngology, National Taiwan University Hospital, Taipei (Drs Hsu, Day, and Young); and Institute of Occupational Medicine and Industrial Hygiene, College of Public Health (Drs Hsu and Wang) and Department of Anatomy and Cell Biology, College of Medicine (Dr Lue), National Taiwan University, Taipei.

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