title: Canal conversion and reentry: a risk of Dix-Hallpike during canalith repositioning procedures.
abstract: 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).
  
  
  METHODS
  Prospective case series.
  
  
  METHODS
  Academic tertiary referral center.
  
  
  METHODS
  Forty-four patients with symptomatic posterior canalithiasis (P-BPPV) confirmed on Dix-Hallpike.
  
  
  METHODS
  Up to 5 CRP for initial P-BPPV and additional maneuvers for canal conversion or reentry in 1 session.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Otolaryngology, University of Colorado Denver School of Medicine, Aurora, Colorado, USA. carol.foster@ucdenver.edu
authors.forename: Carol A
authors.initials: CA
authors.lastname: Foster
authors.forename: Kathleen
authors.initials: K
authors.lastname: Zaccaro
authors.forename: Darcy
authors.initials: D
authors.lastname: Strong
mesh_terms: D065635:Benign Paroxysmal Positional Vertigo; D005221:Fatigue / Q000209:etiology; D006801:Humans; D020347:Lithiasis / Q000150:complications / Q000473:pathology / Q000601:surgery*; D009759:Nystagmus, Pathologic / Q000209:etiology; D013506:Otologic Surgical Procedures / Q000009:adverse effects* / Q000379:methods*; D011183:Postoperative Complications / Q000453:epidemiology; D011446:Prospective Studies; D012008:Recurrence; D012665:Semicircular Canals / Q000473:pathology / Q000601:surgery*; D016896:Treatment Outcome; D014717:Vertigo / Q000209:etiology*; D015837:Vestibular Diseases / Q000150:complications / Q000473:pathology / Q000601:surgery*