[Effects of high dose steroid on the experimentally induced facial palsy]

As a conservative treatment for Bell's palsy, the high dose steroid therapy introduced by Stennert in 1982 are highly evaluated clinically from many investigators. In the present study, model animals with experimentally-induced facial paralysis were prepared using guinea pigs in which the effect of administration of high dose steroid on the recovery process of the palsy was investigated electrophysiologically and morphologically. The main trunk of the facial nerve was exposed under Nembutal anesthesia, and compressed for 10 sec. using a needle holder. The model animals were divided into three groups, a high dose steroid group (Group A) and a low dose steroid group (Group B) and control group (Group C). The evoked EMGs of orbicularis oris muscle were recorded before operation and on the third, seventh and 14th days after operation, and each time course of the amplitude changes in Groups A, B and C was compared. Recovery patterns of amplitude in Group A was much more rapid than in Groups B and C. Light microscopy revealed extensive destruction and existence of only a small number of normal myelinated fibers on the 14th day after operation in Group C. In Group A, however, these changes were slight. And the numbers of normal myelinated fibers decreased to a minimum in Group C, while the number of fibers in Group A already increased on the 14th day. Electron microscopy, in Group C, disclosed distortion of the sheath of myelinated fibers and abnormal changes in the axon. But in Group A, dense lamellar structure of myelin sheath and no axonal degeneration were disclosed. These experimental results support the efficacy of high dose steroid therapy upon Bell's palsy.