A Case of Extratemporal Facial Nerve Schwannoma in Parotid Gland Diagnosed Intraoperatively

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  • Oka Aiko
    Department of Otolaryngology, Head and Neck Surgery, Kurashiki Central Hospital
  • Oono Tsunehisa
    Department of Otolaryngology, Head and Neck Surgery, Kurashiki Central Hospital
  • Iwanaga Ken
    Department of Otolaryngology, Seirei Hamamatsu Hospital
  • Sato Shin-ichi
    Department of Otolaryngology, Head and Neck Surgery, Kurashiki Central Hospital

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Facial nerve schwannomas may occur in any segment of the facial nerve, from the cerebellopontine angle to the parotid gland. Extracranial facial nerve schwannomas are uncommon, and tumors around parotid grand may be misdiagnosed as parotid tumors, such as pleomorphic adenoma or Warthin’s tumor. Facial paralysis should be borne in mind as a complication of surgical treatment for facial nerve schwannoma. We encountered a case of extratemporal facial nerve schwannoma that was preoperatively diagnosed as a parotid tumor, but intraoperatively confirmed as a facial nerve schwannoma.<br>A 35-year-old female was referred to us because of a slight swelling in the anterior part to the right ear. The swelling was slightly tender, but there was no facial paralysis. Physical examination revealed a mass measuring about 3 cm in diameter, that was elastic in consistency and freely mobile. Magnetic resonance imaging (MRI) showed a solid tumor anterior to the parotid grand, visualized as a hypointensity on T1-weighted images and as a well-circumscribed hyperintensity on T2-weighted images. Fine-needle aspiration biopsy revealed class I cytology. Based on these findings, a parotid tumor was suspected, and surgical resection was undertaken. The intraoperative histopathology revealed a schwannoma with an influx of peripheral facial nerve fibers. The postoperative clinical course was good, and there has been no facial paralysis or recurrence during the 10 months since the surgery.<br>The preoperative diagnosis of facial nerve schwannoma is difficult because of the lack of dindistinctive MRI findings and the low diagnostic sensitivity of fine-needle aspiration biopsy. If the tumor is diagnosed as schwannoma preoperatively or intraoperatively, its location and the pre-operative facial nerve function can affect the decision on the surgical treatment. While functional preservation should be an important goal of surgical treatment, complete removal is also important, as subtotal resection has been shown to be associated with unacceptably high recurrence rates in the long term.

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