Measurement of the Facial Nerve Caliber in Facial Palsy

Abstract

The clinical effectiveness of facial nerve decompression remains controversial. To investigate this problem, we observed changes in the facial nerves of patients with and without facial palsy after this procedure. Retrospective case review. Tertiary referral center. Fifteen cases who underwent opening of the facial canal under total mastoidectomy were enrolled for this study. Among these, 7 patients with Bell's palsy (House-Brackmann grade VI) underwent facial nerve decompression. The remaining 8 patients with temporal bone tumors did not show facial palsy and underwent rerouting or grafting of the facial nerve. After removal of the bone around the facial nerve, various parameters regarding the facial nerve (including the nerve width) were carefully observed, measured, and recorded. These values were subsequently compared using the Student's t test. After removal of the bony covering, swelling of the facial nerve was observed in all 7 patients with facial palsy, and nerves dilated in diameter by 12% to 32% (mean, 21.0 ± 6.1%). Injection and exudate also were observed among these patients. Swelling of the facial nerve was not observed in 8 patients without facial palsy before surgery (mean, 0.6 ± 1.2%). A statistically significant difference was observed between the 2 groups (p < 0.01). In the present study, edema of the facial nerve was not observed in patients without facial palsy. Although the present study has limitations and do not necessarily justify decompression, these different findings suggest that nerve decompression relieves the entrapment of the facial nerve.