1

Introduction

Cochlear implants are used worldwide for the treatment of severe to profound bilateral sensorineural hearing loss in both adults and children. A number of implantees are likely to be treated with radiosurgery later in life, but very little is known about the effects of radiosurgery on cochlear implants. Only 4 studies have focused on the influence of radiation therapy on cochlear implant function in vitro . This is the first report addressing the effects of radiosurgery in a patient with a cochlear implant.

2

Case report

A 48-year-old woman complained of right total deafness, present since childhood. In 1992, the patient developed left total deafness due to suppurative labyrinthitis, which developed secondary to left chronic otitis media. In 1993, she underwent a left tympanoplasty, and we planned left cochlear implantation. The next year, she underwent left cochlear implantation (CI 22M, Cochlear Ltd, Sydney, Australia) in our clinic. After implantation, the impedances of the electrodes were stable. Auditory performance (SRT 40dB, HINT scores 50/50) was excellent, and the categories of auditory performance scores were 7 . There were no specific problems for ten years. In 2004, the patient complained of sudden dizziness. Computed tomographic brain scans demonstrated a high density, 2.8-cm diameter mass in the right supratent and infratent area ( Fig. 1 ). We suspected a meningioma and transferred the patient to the neurosurgical clinic. Two months later, tumor removal was performed by a neurosurgeon via a right subtemporal craniotomy approach. Histopathological examination disclosed a meningioma. The patient’s postoperative course was uneventful. We checked follow-up computed tomographic scans twice a year, and the 2007 follow-up computed tomographic scans revealed a 1.5-cm diameter mass at the same site. We did not check magnetic resonance imaging because the patient refused the demagnetization of implant. We decided to pursue radiosurgery for treatment of this recurrent meningioma because the patient refused surgery. Before pursuing this course of treatment, we explained the risk of implant failure to the patient. She had received a 26-Gy dose of radiosurgery in a single fraction.

Axial computed tomographic scans showing a high-density mass in the right supratent and infratent area.

After radiosurgery, the impedances of the implant were still stable and auditory performance tests (SRT 40dB, HINT scores 50/50, and categories of auditory performance scores 7) were unchanged as compared to before the procedure. The patient was followed up for 2 years after radiosurgery, and auditory performance remained excellent.