Myoneural Junctions of Extraocular Muscles: Distances from the Orbital Rim and Widths

Abstract

Purpose: To examine both the distances from the orbital rim to the myoneural junctions (MNJs) and the widths of the MNJs of all extraocular muscles. Methods: Six orbits of 3 post-mortem cadavers were used. The cadavers (1 female and 2 males) were all Japanese with an average age of 76.3 years. The MNJs of the extraocular muscles and their motor nerves were exposed, and then the distance from the orbital rim to each MNJ and the width of each MNJ were examined. Results: The distance from the orbital rim to each MNJ in the 6 extraocular muscles ranged from 24.4 to 33.6 mm and the width of each MNJ ranged from 5.0 to 8.5 mm. Conclusions: It is essential for orbital surgeons to understand both the distance from the orbital rim to MNJs and the widths of MNJs. This information not only aids the understanding of MNJ damage, but also prevents iatrogenic nerve impairment during orbital surgery.

Intraorbital Abducens Nerve Schwannoma

“…Based on the work of Erdogmus et al (8), Irace et al (13) proposed that the entry point of nerve fibers in the muscle (e.g., area nervosa or myoneural junction) (15) is the zone where intraorbital schwannomas truly arise. Similar to the description by Irace et al (13), in our case, we were able to demonstrate, preoperatively by MRI (Figure 2) and intraoperatively by identifying the area of attachment of the tumor, the origin of the schwannoma from the abducens nerve.…”

Orbital Abducens Nerve Schwannoma: A Case Report and Review of the Literature

“…Based on the work of Erdogmus et al, 7) Irace et al 5) proposed that the entry point of nerve fibers in the muscle (e.g., area nervosa or myoneural junction) 8) is the zone where intraorbital schwannomas truly arise. When performing intraorbital surgery, anatomic knowledge of the innervation of the extraocular muscles allows the minimization of damage to the neural structures.…”

Dissection of the Eyelid and Orbit with Modernised Anatomical Findings

“…5-1). The oculomotor nerve to the inferior oblique muscle travels along the lateral side of the inferior rectus muscle and inserts into the muscle belly on the optic nerve side, in an area between the inferior oblique muscle and the inferior rectus muscle [45,46] (Fig. 5-1).…”

“…All the neuromuscular junctions, except that of the superior oblique muscle, are located on the optic nerve side. The trochlear nerve inserts into the muscle from superiorly on the orbital wall side [45,46] (Fig. 5-2).…”

“…The oculomotor nerve to the LPS muscle travels initially with the oculomotor nerve to the superior rectus muscle (superior branch of the oculomotor nerve), but branches off medially to travel further anteriorly to reach the LPS muscle [10,45,46] (Fig. 5-2).…”