Facial Nerve Paralysis due to a Pleomorphic Adenoma with the Imaging Characteristics of a Facial Nerve Schwannoma

Abstract

Background Facial nerve paralysis in a patient with a salivary gland mass usually denotes malignancy. However, facial paralysis can also be caused by benign salivary gland tumors. Methods We present a case of facial nerve paralysis due to a benign salivary gland tumor that had the imaging characteristics of an intraparotid facial nerve schwannoma. Results The patient presented to our clinic 4 years after the onset of facial nerve paralysis initially diagnosed as Bell palsy. Computed tomography demonstrated filling and erosion of the stylomastoid foramen with a mass on the facial nerve. Postoperative histopathology showed the presence of a pleomorphic adenoma. Facial paralysis was thought to be caused by extrinsic nerve compression. Conclusions This case illustrates the difficulty of accurate preoperative diagnosis of a parotid gland mass and reinforces the concept that facial nerve paralysis in the context of salivary gland tumors may not always indicate malignancy.

Salivary gland tumours: a retrospective study at a tertiary care centre in South India

“…These neoplasms are more likely to occur in relatively old age (6th decade), benign salivary gland tumors usually occur relatively earlier (4-5th decade). [8][9][10] Benign salivary gland neoplasms are more common in females whereas malignant tumours show equal distribution amongst males as well as females. The most common salivary glands to be involved in neoplastic pathology include parotid gland followed by submandibular gland and sublingual gland.…”

“…9,10 Almost 80% salivary gland neoplasms arise in parotid gland followed by submandibular gland (10-15%) and sublingual and minor salivary glands which is in concurrence with the results obtained in this study. 10 Salivary gland tumours have been uniformly reported to be more common in females as compared to males. 11 Torabinia et al conducted an epidemiological study of 229 medical records of patients with salivary gland neoplasms for 10 years duration.…”

Facial nerve palsy due to a parotid abscess: Two case reports and a review of literature

“…Therefore, a malignancy should be ruled out in patients with a parotid mass and facial nerve dysfunction. There are, however, several case reports in the literature that have described benign lesions such as pleomorphic adenoma [17] , (cystic) Warthin tumors [18] , [19] , (lympho)epithelial cysts [20] , [21] , epidermoid cysts [22] , keratocystomas [23] , oncocytomas [24] and intraparotid facial nerve schwannomas [25] to cause peripheral facial nerve palsy.…”

Oncocytoma of the Parotid Gland with Facial Nerve Paralysis

“…Similar cases have been reported in the literature. Histopathologically, Warthin's tumor is the most commonly reported [ 1 – 5 ], with pleomorphic adenoma [ 6 , 7 ] and lipoma [ 15 ] also reported. Only 2 cases of oncocytoma with facial nerve paralysis have been reported to date [ 16 , 17 ], with one patient showing painful swelling in the parotid area similarly to that observed in our case [ 16 ].…”

“…Parotid tumor with facial nerve paralysis is generally considered as a criterion for malignancy. However, several case reports have documented benign tumors of the parotid gland with facial nerve paralysis, with almost all of these cases diagnosed as Warthin's tumor [ 1 – 5 ] or pleomorphic adenoma [ 6 , 7 ]. Oncocytomas are rare benign tumors that comprise about 0.1 to 1.5% of all salivary gland tumors [ 8 ].…”