Canal conversion between anterior and posterior semicircular canal in benign paroxysmal positional vertigo.

OBJECTIVE: To investigate the characteristics of canal conversion between the anterior and posterior semicircular canals in benign paroxysmal positional vertigo (BPPV).

STUDY DESIGN: Retrospective chart review.

SETTING: Secondary referral center.

PATIENTS: A total of 709 patients who were treated with the Epley maneuver for BPPV of the anterior or posterior semicircular canal.

INTERVENTIONS: Vestibular examinations with videonystagmography and the canalith repositioning procedure (CRP) to treat BPPV.

RESULTS: Canal conversion between the anterior and posterior semicircular canals was observed in 18 (2.9%) patients who underwent CRP. In 13 (2.3%) of 564 patients initially diagnosed with posterior canal BPPV (PC-BPPV), switch to anterior canal BPPV (AC-BPPV) was observed at a follow-up visit. In 5 (12.1%) of 41 patients who presented with AC-BPPV, canal switch to PC-BPPV occurred more frequently (p = 0.005). The average number of CRPs before nystagmus resolution was 3.6 in conversion cases versus 1.6 in the nonconversion group (p < 0.001).

CONCLUSION: Canal conversion between the anterior and posterior semicircular canals can occur during treatment. The possibility of canal conversions should be considered for appropriate management of BPPV of the vertical semicircular canals.