Skull Base Carcinoma Ex-Pleomorphic Adenoma: A Hidden Cause for Facial Paralysis

Introduction: Thirty-three percent of patients with malignant parotid tumors develop facial nerve paresis or paralysis.¹ Facial nerve palsy in parotid cancer is correlated with higher tumor stage and more aggressive histologic type and portends a poorer prognosis.¹ We present a case of facial nerve palsy in a patient with a carcinoma ex-pleomorphic adenoma and concomitant lymphoma.

Materials and Methods: This is a case report of a carcinoma ex-pleomorphic adenoma of the parotid gland causing facial nerve paralysis at a tertiary care academic medical center.

Discussion: A 55-year-old woman with no significant past medical history presented to an otolaryngologist with persistent right ear pain and facial paralysis. She was diagnosed with Bell’s palsy and treated with steroids. Her paralysis did not improve, so workup with an MRI neck revealed a cystic tumor in the deep lobe of her right parotid gland. She was referred to our institution for surgical consultation. On exam, there was no palpable parotid mass, but she was a House Brackman II and IV on the right side. Additional imaging with PET and CT imaging revealed a 3-cm right pre-styloid cystic parotid tumor, a sub centimeter level II lymph node, and a right tonsil mass with increased FGD uptake ([Fig. 1]). FNA biopsy returned as high-grade carcinoma and pathology from the tonsil mass biopsy revealed lymphoma. She was taken to the operating room for right pre-auricular infratemporal approach, transmastoid facial nerve decompression with resection, radical total parotidectomy with partial mandibulectomy, neck dissection, ALT free flap, platinum eyelid weight, neurorrhaphy, and interposition nerve grafting for facial reanimation. After skeletonization of the facial nerve, it was transected proximal to the stylomastoid foramen. The facial nerve margins were negative for carcinoma. The parotid tumor was successfully removed, and final pathology revealed carcinoma ex-pleomorphic adenoma with positive extra nodal extension and perineural invasion, and 12 out of 25 positive lymph nodes (pT3N3b). Facial reanimation was performed with a 7-cm cable graft taken from a branch of the femoral nerve and connected to the buccal branch of the facial nerve. The interposition nerve graft did not stimulate at 1 mAmp. Following surgery, the patient is to receive adjuvant radiation therapy for her parotid malignancy and chemotherapy for her lymphoma.

Fig. 1 (Left) Axial T1 post MRI with red arrow pointing to cystic deep lobe parotid mass; (Right) PET-CT showing increased FDG uptake at right tonsil.

Conclusion: While facial paralysis in the setting of parotid malignancies is common, this case demonstrates the importance of thorough workup for patients presenting with facial weakness. This patient was incorrectly diagnosed with Bell’s palsy and was eventually found to have an aggressive parotid tumor undetectable on physical exam. Additionally, she was diagnosed with lymphoma incidentally found on PET CT.

Publication History

Article published online:
07 February 2025