[Ultrastructural study of proprioceptors in extraocular muscles of congenital nystagmus subjects].

OBJECTIVE: To observe the ultrastructure and the light microscopic structure alterations of the proprioceptors in the extraocular muscles (EOM) of congenital nystagmus (CN) subjects and discuss the probable effect and its mechanism of these alterations on CN to approach a new reasonable treatment for CN. METHODS: Twenty-one proprioceptors (muscle spindles) from 8 extraocular muscles of two typical CN were studied under both light microscope and transmission electron microscope. They were compared with 15 proprioceptors obtained from normal fresh cadavers. RESULTS: The proprioceptors in the EOM of CN subjects were smaller and their inner capsules became collapsed, discontinuous and vacuolated. At the same time, the muscle fibers and some endings of sensory nerves of EOMs from CN also had degenerative ultrastructural changes. CONCLUSIONS: The ultrastructure of the proprioceptors, muscle fibers and nerve endings in the EOMs of CN subjects are all changed compared with that of the controls. These alterations probably affect EOM's function and its proprioceptive input, which are probably related to the etiology and pathogenesis of CN.