Neuroanatomy of the extraocular muscle tendon enthesis in macaque, normal human, and patients with congenital nystagmus.

PURPOSE: To search for the presence of, and qualitatively characterize the microscopic anatomy of, nerve terminals in the tendino-scleral (enthesial) area of the extraocular muscle tendon.

METHODS

Extraocular rectus muscle tendino-scleralspecimens from a macaque monkey, a normal human, cadavers, and patients with congenital nystagmus were obtained and studied with transmission electron microscopy.

RESULTS

Enthesial neurovascular structures were identified in all specimens. The enthesial area showed structures consisting of myelinated and unmyelinated nerve fibers with associated supporting vascular capillaries. Qualitative analysis showed anomalous neurovascular structures were in the enthesis of patients with congenital nystagmus.

CONCLUSIONS

This study confirms the presence of normal and abnormal neural anatomy in the enthesial area of the extraocular muscle tendon. Neurovascular abnormalities in the enthesial part of the extraocular muscle tendon may be a result of, or contribute to, disease pathogenesis. If these structures are related to afferent central nervous system input, then disruption of them during surgery might influence postoperative outcome.