Unusual Metastasis to the Petrous Bone Causing Unilateral Facial Paralysis

Introduction: Unilateral facial paralysis is common and has many possible causes. This case describes a rare etiology that should be considered in the differential diagnosis.

Case Study: A 70-year-old laryngectomee was referred after 3 months of right conductive hearing loss and painless purulent otorrhea unresponsive to tympanostomy tube and topical antibiotic drops. Complete right facial paralysis subsequently developed over one week. In addition to prior laryngeal cancer, he had metachronous cancer of the right lateral tongue base treated with resection, pectoralis major myocutaneous flap reconstruction, and postoperative radiation therapy about one year prior to presentation.

CT scan of the temporal bones revealed a destructive soft tissue mass in the external ear extending into the petrous apex. With concern for malignant otitis externa with destructive skull base osteomyelitis, mastoid and ear canal tissue culture was taken and debridement/biopsy around the paralyzed facial nerve was accomplished by mastoidectomy. Examination of the tissue revealed squamous cell carcinoma. Subsequent PET/CT scan of the head and neck revealed a hypermetabolic mass under the pharyngeal myocutaneous flap, suggesting recurrent malignancy as the source of metastasis to the temporal bone.

Conclusion: This case is one of a few reports of facial paralysis due to petrous apex metastasis from previously treated squamous cell carcinoma of oropharynx. The case also illustrates that patients with suspected malignant otitis externa who do not respond to antibiotics require biopsy.

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