Active Middle Ear Implant in a Patient with Neurofibromatosis Type 1 and Multiple Calvarial Defects: A Case Report

Bony abnormalities, including sphenoid dysplasia and calvarial defects, are well recognized in patients with neurofibromatosis type 1. However, having multiple calvarial defects is rare. We present a case of a 35-year-old Japanese male patient who was referred to our hospital because of hearing loss. He was diagnosed with neurofibromatosis type 1 during early childhood. Otoscopic examination revealed a protrusion from the anterior wall of the external auditory canal that obstructed the external auditory canal. Computed tomography findings revealed multiple defects and an uneven skull surface. Large bony defects of the anterior wall of the external auditory canal were also identified bilaterally. Conductive hearing loss was caused by temporomandibular joint herniation that was obstructing the external auditory canal in both ears. An active middle ear implant was implanted in the right ear. A floating mass transducer was placed into the round window niche using a round window coupler. The active middle ear implant improved postoperative audiometric thresholds to approximately 35 dB across all frequencies. No complications occurred for up to 30 months after the operation. An active middle ear implant is a feasible and valuable option for patients with neurofibromatosis type 1 and conductive hearing loss due to multiple skull defects that result in temporomandibular joint herniation.