A comparison and conversion table of 'the House-Brackmann facial nerve grading system' and 'the Yanagihara grading system'.

A comparison between the House-Brackmann facial nerve grading system (the HB-system) and the Yanagihara grading system (the Y-system) was studied with 199 evaluations of 62 cases of postoperative unilateral acoustic neuroma. In the beginning, an original draft of the conversion table was formulated according to the 199 evaluations, in which, 0-6, 8-14, 16-20, 22-28, 30-38, and 40 points in the Y-system were matched with grade VI, V, IV, III, II, and I in the HB-system respectively. The result of the present study for prediction of sequelae showed that it was not necessary to consider the sequelae in a conversion table. And more, the study of an inter-observer variation showed that the lower and upper limits of the scores in the Y-system may shift within about a 2-point range in the draft table. From these aspects, a newly revised conversion table was proposed as a revised conversion table, in which, 0-6, 8-14, 16-22, 24-30, 32-38, and 40 points in the Y-system were matched with grade VI, V, IV, III, II, and I in the HB-system. This revised conversion table is much easier to remember for clinical use, because the score of the lower limit of each grade is simply in multiples of 8, that is, 0, 8, 16, 24, 32 and 40.