Vascular Anomaly in the Fallopian Canal Encountered Unexpectedly During Cochlear Implantation

A 68-year-old male with progressive sensorineural hearing loss underwent left cochlear implant surgery. While developing the posterior tympanotomy and identifying the facial nerve mastoid segment, gentle stimulation by the nerve stimulator resulted in unexpected profuse venous bleeding. After achieving hemostasis with Surgicel and Spongostan, the posterior tympanotomy was extended exposing a large aberrant vein running parallel to the tympanic and mastoid segments of the facial nerve in the fallopian canal. Good exposure and careful palpation of the vein assisted in ruling out facial nerve hemangioma. An intraoperative decision to proceed with implantation, taking into account limited benefit from future magnetic resonance imaging, was taken. The patient had a temporary 3-month post-operative facial nerve weakness, probably from pressure applied during hemostasis. Auditory cochlear implant function was excellent. A larger than normal diameter of the tympanic and mastoid segments of the facial nerve was seen in re-reviews of the preoperative computed tomography. We believe drawing the readers' attention to this anomaly, which to the best of our knowledge has not been previously described, can assist in the choice of preoperative imaging and increase awareness of deviation from the norm of facial nerve diameter. In addition, knowledge of possible venous anomalies may aid surgeons in such intraoperative decisions.