Transient low-tone air-bone gaps during convalescence immediately after canal plugging surgery for BPPV

Abstract

Objectives: The aim of the present study was to elucidate the time course and frequency patterns of transient low-tone air-bone gaps (ABGs) after canal plugging for intractable BPPV.

Methods: We investigated eight patients with intractable BPPV who underwent canal plugging. Four were cases with posterior type (pBPPV) and the other four were those with horizontal type (hBPPV). Pure-tone audiometries (PTAs) were performed before and 7 days, 1 month and 6 months after surgery. ABGs (+) were defined as the three-tone-average ≥20dB formulated by (a+b+c)/3, where a, b, and c are ABGs at 0.25, 0.5, and 1kHz, respectively.

Results: The ratio of the number of patients with ABGs (+) at the post-operative 7th day and 1st month was 100.0% (8/8). The ratio at the post-operative 6th month was 0.0% (0/8). There were no significant differences in the time course or frequency patterns of the ABGs between pBPPV and hBPPV.

Conclusions: We clearly demonstrated eight cases with intractable BPPV showing transient low-tone ABGs during convalescence immediately after canal plugging. During that period, patients also complained of motion-evoked dizziness. All these findings suggest that, during such a convalescence period, the plugged area might not be fixed yet and could still induce the dizziness and low-tone ABGs, as enlarged vestibular aqueduct syndrome and superior semicircular canal deficiency syndrome exhibit low-tone ABGs due to the third mobile inner ear window. More than one month after surgery, both the ABGs and dizziness could disappear according to fixation of the plugged area.