Canal conversion and reentry: a risk of Dix-Hallpike during canalith repositioning procedures.

OBJECTIVE To determine the incidence, cause, and prevention of horizontal canal benign paroxysmal positional vertigo (H-BPPV) and reentry into the common crus during canalith repositioning procedures (CRPs). STUDY DESIGN Prospective case series. SETTING Academic tertiary referral center. PATIENTS Forty-four patients with symptomatic posterior canalithiasis (P-BPPV) confirmed on Dix-Hallpike. INTERVENTION Up to 5 CRP for initial P-BPPV and additional maneuvers for canal conversion or reentry in 1 session. MAIN OUTCOME MEASURES Incidence and timing of onset of H-BPPV or common crus reentry and the outcome of treatment maneuvers. RESULTS H-BPPV or reentry occurred during the Dix-Hallpike after a canal-clearing CRP and affected 16% (7/44) of subjects. Approximately 87% (7/8) of reentry or conversion events occurred after the very first CRP. Geotropic H-BPPV occurred in 9% (4/44) overall but in 13% (4/30) whose P-BPPV was resolved by a single CRP. All were cleared with H-BPPV maneuvers, 3 of 4 resolving with a single Gufoni maneuver. Approximately 9% (4/44) of patients developed reentry of particles into the common crus. It was treated by raising the patient to the upright position. By waiting 15 minutes after treatment of reentry, a final normal Dix-Hallpike was obtained without causing reentry into any canal in all patients. CONCLUSION If the first CRP clears the posterior canal, there is an elevated risk of reentry or canal conversion if another Dix-Hallpike is performed immediately. These complications can be treated by additional maneuvers; if unfamiliar with these techniques, the risk can be reduced by waiting at least 15 minutes between repetitions of CRP.