title: Carhart notch 2-kHz bone conduction threshold dip: a nondefinitive predictor of stapes fixation in conductive hearing loss with normal tympanic membrane.
abstract: OBJECTIVE
  To evaluate the significance of the Carhart notch (a 2-kHz bone conduction threshold dip [2KBD]) in the diagnosis of stapes fixation by comparing its incidence among ears with various ossicular chain abnormalities.
  
  
  METHODS
  Retrospective study.
  
  
  METHODS
  University hospital.
  
  
  METHODS
  A total of 153 ears among 127 consecutive patients with a congenital ossicular anomaly or otosclerosis.
  
  
  METHODS
  The 2KBD depth was defined as the threshold at 2 kHz minus the mean of thresholds at 1 and 4 kHz. The presence of 2KBD (depth, ≥10 dB), 2KBD depth, relationship between 2KBD depth and air-bone gap, and 2-kHz bone conduction recovery after operation were evaluated in a stapes fixation group (which included cases of otosclerosis and congenital stapes fixation), an incudostapedial joint detachment group, and a malleus or incus fixation group.
  
  
  RESULTS
  A 2KBD was present in 32 of 102 stapes fixation ears (31.4%), 5 of 19 incudostapedial joint detachment ears (26.3%), and 6 of 20 malleus or incus fixation ears (30.0%) (12 ears had other diagnoses). The mean (SD) 2KBD depths were 17.3 (5.2) dB in the stapes fixation group, 18.5 (2.2) dB in the incudostapedial joint detachment group, and 16.3 (2.1) dB in the malleus or incus fixation group. No statistically significant differences were noted among these 3 groups. No correlation was noted between 2KBD depth and air-bone gap extent. Recovery of 2-kHz bone conduction threshold in the stapes fixation group was less than that in the other 2 groups.
  
  
  CONCLUSIONS
  Incidence of 2KBD was similar among the stapes fixation, incudostapedial joint detachment, and malleus or incus fixation groups, implying that 2KBD is not a useful predictor of stapes fixation.
authors.affiliation: Department of Otolaryngology, Teikyo University School of Medicine, 2-11-1 Kaga Itabashi-ku, Tokyo, Japan.
authors.forename: Akinori
authors.initials: A
authors.lastname: Kashio
authors.forename: Ken
authors.initials: K
authors.lastname: Ito
authors.forename: Akinobu
authors.initials: A
authors.lastname: Kakigi
authors.forename: Shotaro
authors.initials: S
authors.lastname: Karino
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Iwasaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Sakamoto
authors.forename: Takuya
authors.initials: T
authors.lastname: Yasui
authors.forename: Mitsuya
authors.initials: M
authors.lastname: Suzuki
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Yamasoba
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001309:Auditory Threshold / Q000502:physiology*; D001844:Bone Conduction / Q000502:physiology*; D002648:Child; D004429:Ear Ossicles / Q000002:abnormalities* / Q000503:physiopathology*; D006314:Hearing Loss, Conductive / Q000175:diagnosis* / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D008875:Middle Aged; D010040:Otosclerosis / Q000175:diagnosis* / Q000503:physiopathology* / Q000601:surgery; D011183:Postoperative Complications / Q000503:physiopathology; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D013199:Stapes / Q000002:abnormalities* / Q000503:physiopathology*; D013200:Stapes Mobilization; D055815:Young Adult