Objective: The aim of this study was to evaluate the accuracy of the Yanagihara facial nerve grading system in assessing the course of recovery and in determining the probability of a complete recovery of Bell's palsy within 1 week after onset.
Study design: Retrospective study of patients at a single trial center.
Setting: Tertiary referral center.
Patients: Six hundred sixty-four patients with Bell's palsy were assigned to three groups by degree of facial palsy using the Yanagihara 40-point system.
Main outcome measure: The rate of recovered patients was assessed until 6 months after onset.
Results: Ultimately, 151 (23.1%) patients were assessed with mild palsy, 286 (43.7%) with moderate palsy, and 217 (33.2%) with severe palsy. The average Yanagihara score in the recovered patients was 15.7, whereas the score in the nonrecovered patients was 8.4. The rate of recovered patients in the mild group was 99.3%, that in the moderate group was 95.1%, and that in the severe group was 80.2%. These differences among the groups were significant (p < 0.05).
Conclusion: The Yanagihara system was able to distinguish the probability of a complete recovery of the facial palsy within 1 week after the onset of palsy. We believe that the key point in improving the prognosis of Bell's palsy is to diagnose the severity, using the Yanagihara system, and to treat it promptly to prevent progressive nerve degeneration.