What is the most important factor to preserve hearing in lateral semicircular canal fistula surgeries, fistula size or bony structure?

PURPOSE: Cholesteatoma on lateral semicircular canal (LSCC) fistula > 2 mm in size is likely to be unmanipulated due to the risk of sensorineural hearing loss. However, the matrix can be successfully removed without hearing loss when it is > 2 mm. The purpose of the study was to evaluate surgical experience over the past 10 years and to suggest the important factor for the hearing preservation in LSCC fistula surgeries.

METHODS

According to the fistula size and symptoms, 63 patients with LSCC fistula were grouped as follows: Type I (fistula < 2 mm), Type II (≥ 2 mm and < 4 mm without vertigo), Type III (≥ 2 mm and < 4 mm with vertigo), Type IV (≥ 4 mm), and Type V (any size fistula but with deafness at the initial visit). The cholesteatoma matrix was meticulously manipulated and removed by experienced surgeons.

RESULTS

Only two patients completely lost their hearing after surgery (4.5%). However, the loss was inevitable because their cholesteatomas were highly invasive and there was also facial nerve canal involvement; thus, the bony structure of the LSCC was already destroyed by the cholesteatoma. Unlike these two Type IV patients, Type I-III patients, and those with a fistula size < 4 mm, did not lose their sensorineural hearing. If the structure of the LSCC was maintained, hearing loss did not occur even if the fistula size ≥ 4 mm.

CONCLUSIONS

The preservation of the labyrinthine structure is more important than the defect size of the LSCC fistula. If the structure is intact, cholesteatoma matrices lying on the defect can be safely removed, even though the size of bony defect is large.