Hyrtl's fissures in cochlear implant surgery.

This case study presents a rare anatomical anomaly complicating cochlear implantation in the form of patent periotic ducts and Hyrtl's (tympanomeningeal) fissures. Hyrtl's fissures are transient anatomical conduits which normally ossify by the 24th week of gestation. Their persistence may cause inadvertent insertion of the cochlear implant electrode into this channel and prevent a successful outcome. This case study and a review of the relevant literature highlights the importance of recognizing this rare anomaly which is easily missed on preoperative imaging.