Ultrastructural Study of Extraocular Muscle in Congenital Nystagmus

Abstract

To determine the mechanism of congenital nystagmus (CN), the ultrastructure of the extraocular muscle in CN patients was examined with the transmission electron microscope. The specimen of muscle tissue was taken during surgery from horizontal recti in the slow and quick phase sides separately in the jerky type, and medial and lateral recti in the pendular type. The extraocular muscle was immediately fixed in 2.5% glutaraldehyde solution. (1) In the jerky type, the myocytes in the quick phase side showed myofibrillae that were perpendicular to axes of myocytes and had the structure of sarcomeres. In the slow phase side there were perpendicular myofibrillae in the periphery of myocytes. (2) In the pendular type, there were no perpendicular myofibrillae within myocytes. The myofibrillae that were parallel to the axes of myocytes were arranged disorderly. The length of the H and I bands in different myofibrillae was not identical. These results demonstrated, for the first time, the ultrastructural changes in the extraocular muscle of CN patients, which might provide the pathological basis for this disease.

A Gene for X-Linked Idiopathic Congenital Nystagmus (NYS1) Maps to Chromosome Xp11.4-p11.3

“…Indeed, recent studies by Dell'Osso et al (1992a, 1992b, 1992c showed that CN patients had intense fixation reflexes and stable pursuing eye movements with normal vestibulo-ocular reflexes (ocular-stabilization systems) and proposed that CN was caused by unstable efferent impulses from the extraocular muscles. Ultrastructural studies support the disorganization of the architecture of the extraocular muscles, with degenerative changes of the mitochondria in CN patients (Adachi et al 1973;Pepin et al 1980;Mencucci et al 1995;Peng et al 1998). Yet, it also has been suggested that the extraocular muscle changes are secondary to nystagmus (Hamed 1995).…”

Extraocular Muscles in Patients With Infantile Nystagmus

“…Several studies 22,23 have examined EOMs from patients with ocular motility disorders, including EOMs from patients diagnosed as having infantile nystagmus, but these studies focused on EOM ultrastructure and pathologic characteristics at the single-fiber level. Several abnormalities were described in these studies, including myofibrillar disruption and abnormal mitochondria.…”

Identification of a novel GPR143 mutation in a large Chinese family with congenital nystagmus as the most prominent and consistent manifestation

“…It may result from instability of the ocular motor system (Dell'Osso and Flynn 1974). Changes in the ultrastructure of the extraocular muscle of congenital nystagmus patients have been detected by transmission electron microscopy (Peng et al 1998). It is likely that the GPR143 mutations may disrupt a key signal-transduction pathway and cause instability in the motor system controlling the eye movement.…”