Evaluation of Fallopian Canal Dehiscence in Mastoid Surgeries

The risk of iatrogenic facial nerve injury increases in presence of Fallopian canal dehiscence during mastoid surgeries. This study aimed to find out the incidence, site, and size of Fallopian canal dehiscences and their pre-operative & intra-operative predictors. Prospective cross-sectional observational study. 46 patients of chronic otitis media (COM) undergoing canal wall down (CWD) mastoidectomy at a tertiary care centre in Uttarakhand, India. Fallopian canal dehiscence was encountered in 50% cases (23/46) and its most frequent site was the tympanic segment in 73.9% cases while the least frequent site was mastoid segment in 2.2% cases. Most of the dehiscences were more than 4 mm in size at 69.6%. Fallopian canal dehiscence was found in 100% of cases with preoperative facial palsy, 66.7% cases with aural polyps, 75% of cases with hearing loss > 90 dBHL, and in 100% of the cases with eroded dural plate and sinus plate on X Ray mastoid. Intraoperatively, Fallopian canal dehiscence was found in 70% of cases with LSCC fistula, and 66.7% cases of sigmoid plate erosion. Fallopian canal dehiscence is seen in 50% of cases undergoing CWD mastoidectomies, with most common site being the tympanic segment. Surgeons should be vigilant in cases of revision mastoidectomy, preoperative facial palsy, aural polyps, hearing loss > 90 dBHL, and cases with sinus plate and/or dural plate erosions on X Ray mastoid. The surgeon should be cautious to prevent facial nerve injury if they encounter a LSCC fistula, and sigmoid plate erosion intraoperatively.