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.