Surgical results of cochlear implantation in malformed cochlea

Objective: To report the surgical aspects of cochlear implantation in malformed cochlea. Setting: Tertiary care center. Study Design: Retrospective case review. Methods: Between November 1997 and October 2004, 20 patients with inner ear malformations were implanted in our department. The age range was between 2 and 37 years (average, 8.8 yr). The anomalies were classified according to Sennaroglu and Saatci classification. There were two patients with common cavity deformity, four cases of incomplete partition (IP) type I (cystic cochleovestibular malformation), four cases of IP type II (classical Mondini's deformity), nine patients with large vestibular aqueduct (LVA) syndrome, and one patient with X-linked deafness. Results: Standard transmastoid facial recess approach was used in 17 patients (three patients with IP I, four patients with IP II, and nine patients with LVA syndrome). In the remaining patient with IP I, because of the dehiscent and anteriorly located facial nerve, the surgical approach had to be modified, and an anteroposterior approach was used. After elevating the tympanomeatal flap, the electrode was inserted through the ear canal and then transferred to the mastoid through a full-length cut produced in the ear canal. The flap then returned to its place. In the patients with common cavity deformity, the electrode was inserted by the transmastoid labyrinthotomy approach. Facial nerve had an abnormal course in four patients, but no patient had facial weakness postoperatively. Cerebrospinal fluid gusher was encountered in four patients, whereas oozing was present in five patients. It seems that a slightly larger cochleostomy may reduce postoperative rhinorrhea. The patient with common cavity deformity showed abnormal vestibular stimulation which decreased and was totally abolished during a 3-month period. Conclusion: Based on these findings, cochlear implantation is surgically feasible in patients with common cavity, IP types I and II, and LVA. The surgeon should be ready to make modifications in the surgical approach because of the abnormal course of the facial nerve and be ready to produce special precautions to cerebrospinal fluid gusher.