House-Brackmann and Yanagihara grading scores in relation to electroneurographic results in the time course of Bell's palsy

The results of House-Brackmann and Yanagihara grading were compared with electroneurographic (ENoG) data in 30 consecutive patients with Bell's palsy. The examinations were made on mean days 11. 36 and 99. Twenty-four patients had a favourable outcome (Yanagihara greater than or equal to 36 at three months). Based on our observations, 23 (96%) of these could have been predicted by ENoG, 18 (75%) by Yanagihara grading and 6 (25%) by House-Brackmann grading. Initially, the relative House-Brackmann scores showed a slightly milder palsy than the Yanagihara scores, but in the follow-up period the gradings were almost identical. The mild palsies. defined on the initial ENoG results, initially demonstrated relatively less nerve dysfunction on ENoG than the clinical grading; by the first follow-up, the ENoG and clinical grading had both returned to normal. The intermediate palsies had almost the same initial relative clinical and ENoG values, but at the first follow-up (mean day 36); the facial function had returned to normal despite abnormally reduced, but improved, ENoG values. In the severely affected patients, the follow-up studies showed an improved clinical function but ENoG values still demonstrated a high degree of degeneration (slightly improved at second follow-up). In this study. patients with a favourable outcome were best predicted with ENoG. Clinical identification of these patients was more accurate with Yanagihara than with House-Brackmann. Furthermore, in all three groups a clinical improvement, due to the release of neurapraxia, was noted at the first follow-up. The slow ENoG improvement noted at follow-up was probably due to nerve regeneration by collateral sprouting. Based on the time course of our ENoG findings, it appears that patients with a high degree of degeneration at both the initial examination and first follow-up have a poorer prognosis.