ABSTRACT
Background The afferent signals of proprioceptor in extraocular muscles play an important role in controlling eye position and conjugate movement. Palisade ending in the extraocular muscles is the main source of proprioceptive information, and its abnormalities in structure and function may be associated with the occurrence of nystagmus. Objective This study was to observe the changes of palisade ending in the extraocular muscles of patients with congenital nystagmus ( CN) and discuss the probable mechanism. Methods Modified Kestenbaum procedure was performed on 10 patients with CN, and the extraocular muscle samples were collected during the operation. Normal extraocular muscle samples were obtained from the enucleated eyeballs after ocular wound. The ultrathin sections of extraocular muscles were prepared and double-staining by uranyl acetate and lead citrate. The morphological changes of the palisade ending of extraocular muscles were examined under the transmission electron microscopy. Written informed consent was obtained from each subject before surgery. Results The ultrastructure of palisade ending in the extraocular muscle of CN subjects showed the different degrees of alterations. The mild changes included the collapse and disconnection of external capsules and the nonhomogeneous electron-dense substracts. The degeneration and dissociation of myelin in nerve endings, swelling and vacuolation of mitochondria were also exhibited. Myeloid body was found in axon. In the severe patients,the necrosis of Schwann' s cells,dissolve of axon and disappear of capsules were seen. Conclusion The palisade ending of extraocular muscle in the patients with CN are obviously abnormal in comparison with normal one. These alterations are probably associated with the etiology and pathogenesis of CN.