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

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.

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.

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.

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.