Diffuse Hyperostosis of the Skull Base

Background: Bony aberrations of the skull base can commonly occur in the setting of fibrous dysplasia, Paget’s disease, a neoplasm, or an inflammatory process. We present a case of diffuse, idiopathic skull base hyperostosis presumably causing hearing loss, dizziness, and facial dysfunction.

Case Presentation: A 36 year-old Caucasian male presented to our clinic for evaluation of facial stimulation while using a right-sided cochlear implant. Eight years prior, he began experiencing progressive right-sided hearing loss. There was no sudden change in his hearing, and the loss was accompanied by tinnitus and disequilibrium. Over time, his hearing loss progressed slowly in both ears, but more rapidly on the right side. One month prior to his presentation to our institution, he underwent right cochlear implantation at an outside clinic and has since experienced difficulties with facial stimulation during use of the implant. He has no known medical history aside from juvenile cataracts and strabismus. He has no family history of hearing loss or disorders of bony metabolism. His physical exam is unremarkable. Aside from his left-sided strabismus and hearing loss, there is no evidence of cranial neuropathy. CT scan and MRI demonstrate extensive hyperostosis of the skull base bilaterally, which is pronounced at the porus acusticus and visible at most other skull base foramina. His implant electrode array is in place within the cochlea.

Conclusion: There are many intrinsic conditions that can lead to bony malformations of the skull base. In the present case, a clear etiology is not apparent after both CT and MRI. Currently, he is being managed with primary observation to see if his symptoms and radiographic findings evolve. Our presumption is that his facial stimulation with cochlear implant use is being caused by bony changes in the otic capsule that have lowered impedance. Future management questions will be directed toward the treatment of his contralateral hearing loss if it continues to progress and treatment of other cranial neuropathies, if they occur in association with more pronounced hyperostosis.