Learning Objectives: To make otologic surgeons must be familiar with facial recess anatomy on temporal bone CT images. To interpret interpret radiological abnormalities preoperatively to minimize complications during CI surgery. To estimate the width of the facial recess by measuring the distance between the exterbal auditory canal and vertical segment of the facial nerve. To discuss alternative approaches to CI in case of narrow facial recess.

Introduction: Cochlear implantation (CI) is typically performed though a mastoidectomy and posterior tympanotomy approach. Successful implantation via this approach depends upon accurate identification of the round window niche (RWN), which can be difficult in patients with limited RWN visibility.

The facial recess (FR) is defined as the mastoid air cells between the chorda tympani nerve and the vertical segment of the facial nerve (FN). If the space between the external auditory canal (EAC) and the FN is more than 2–3 mm, the width of the facial recess can be considered as normal. We present a case with a narrow FR diagnosed on preoperative CT and provide a description of the surgical technique used for CI.

Case Presentation: A 50-year-old female with bilateral profound sensorineural hearing loss (SNHL) presented for CI evaluation. CT demonstrated the space between the vertical segment of the FN and EAC in her right ear to be normal whereas in the left ear the space was narrow; the vertical segment of the FN was positioned nearly beneath the EAC.Therefore, the bony part of the EAC (approximately 0.5 cm in diameter) adjacent to the FN was removed while preserving the integrity of the overlying skin. This permitted greater access to the middle ear. The electrode array was placed via RW approach uneventfully through this technique. The defect in the EAC was reconstructed with a cartilage graft obtained from the concha and the EAC skin was returned to its original position.

Conclusion: When HRCT images indicate limited RWN visibility, surgeons must be prepared to use alternative procedures rather than the posterior tympanotomy approach alone. Removal of a part the posterior EAC wall can increase RWN exposure instead of further enlargement of the FR. The borders and width of the FR can be estimated by measuring the distance between the EAC and vertical segment of the FN. The optimal surgical method can be chosen intraoperatively by an experienced CI surgeon.