9) conducted a study with 137 patients in whom incus interposition was used and they reported that the air-bone gap
Postoperative air-bone gap
, ABG was in the range of 21--30 db in 15 cases (50%) in Group A followed by 14 cases (46.
Averages of air-conduction thresholds and average air-bone gaps
In addition, they stated that the decrease in air-bone gap
measurements affected hearing positively.
Graphs demonstrate the frequency-specific air-conduction, bone-conduction, and air-bone gap
hearing changes after type I tympanoplasty with use of a powered drill.
Number of Number of Patients Patients (Before Surgery) (After Surgery) <=5dB HL 4 6 6-10 dB HL 17 11 11-15 dB HL 30 42 >16dB HL 11 3 Air-Bone Gap
Number of Number of Patients Patients (Before Surgery) (After Surgery) <=5dB HL 18 4 6-10 dB HL 19 10 11-15 dB HL 14 38 >16dB HL 11 10
On the other hand, in patients with stapedectomy, only 16 patients (64%) developed complete closure of the air-bone gap
(<10 dB) on pure tune audiometry; while in four patients (16%), the airbone gap improved to less 20 dB, recurrent conductive hearing loss in three patient (12%), one patient developed complete sensorineural hearing loss (4%), and one case of fluctuating hearing loss due to reparative granuloma (4%) was reported.
The air-bone gap
(ABG) and hearing gains were evaluated according to the groups.
Moreover, an air-bone gap
of 10 dB or greater was found in 80% (8/10) of patients by PTA.
A previous study conducted by our group found that 53% of the patients with myringostapediopexy (defined by Costa et al (5) as a retraction limited to the postero-superior region, in which there is erosion of the long process of the incus and fixation of the affected TM to the head of the stapes) presented with an air-bone gap
[less than or equal to] 25 dB at all frequencies.
Out of 52 healed perforations, 49 had improvement with air-bone gap
less than 20 dB and rest had air-bone gap
between 20-30 dB.
In patients with raised hearing thresholds, bone conduction was performed, and the air-bone gap
The patient's audiogram showed normal bone thresholds with a 14-dB air-bone gap
9) Anita Krishnan et al observed postoperative air-bone gap
of less than 20 dB is in 75% of cases with quiescent ear and 80% of cases with dry ears who underwent tympanomastoidectomy.
5, 1, 2, and 3 kHz was used to determine mean air- and bone-conduction thresholds, and the postoperative air-bone gap