title: Incidence of horizontal canal benign paroxysmal positional vertigo as a function of the duration of symptoms.
abstract: OBJECTIVE
  The incidence of horizontal canal involvement in benign paroxysmal positional vertigo (HC-BPPV) varies between reports. One of the reasons for these differences is that the duration of symptoms was not considered. Because of the high spontaneous resolution rate in HC-BPPV and the medical referral system, the frequency of HC-BPPV might change according to the duration of symptoms. We evaluated the frequency of involved canals in BPPV according to the duration of symptoms.
  
  
  METHODS
  A retrospective review.
  
  
  METHODS
  A retrospective review was conducted involving 589 patients diagnosed with BPPV from January 2001 to December 2006. The patients were divided into 3 groups according to the duration of symptoms: Group A included patients who sought evaluation in the clinics within 24 hours from the onset of symptoms (n = 328); Group B was composed of patients who experienced symptoms from 24 hours to 7 days (n = 87) before evaluation; and Group C patients had symptoms for more than 7 days (n = 174) before evaluation. The frequencies of involved canals were assessed and compared between the groups. The correlation between the frequency of involved canals and symptom duration was also analyzed.
  
  
  RESULTS
  The posterior, horizontal, and anterior canals were involved in 61.8, 35.3, and 2.9% of the patients, respectively. However, the frequency of HC-BPPV was 40.5% in Group A, 33.3% in Group B, and 26.4% in Group C (p < 0.01). There was a significant negative correlation between the frequency of HC-BPPV and the duration of symptoms (r =-0.670; p < 0.01).
  
  
  CONCLUSIONS
  The incidence of HC-BPPV was higher than reported; however, it significantly decreased according to the duration of symptoms.
authors.affiliation: Department of Otorhinolaryngology-Head and Neck Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Kyu Whan
authors.initials: KW
authors.lastname: Chung
authors.forename: Ki Nam
authors.initials: KN
authors.lastname: Park
authors.forename: Moon Hee
authors.initials: MH
authors.lastname: Ko
authors.forename: Hyung Ki
authors.initials: HK
authors.lastname: Jeon
authors.forename: Jae Yeon
authors.initials: JY
authors.lastname: Choi
authors.forename: Yang-Sun
authors.initials: YS
authors.lastname: Cho
authors.forename: Sung Hwa
authors.initials: SH
authors.lastname: Hong
authors.forename: Won-Ho
authors.initials: WH
authors.lastname: Chung
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009760:Nystagmus, Physiologic / Q000502:physiology*; D012189:Retrospective Studies; D012665:Semicircular Canals / Q000473:pathology*; D013997:Time Factors; D014717:Vertigo / Q000453:epidemiology / Q000473:pathology*; D055815:Young Adult