Intramuscular Distribution of the Abducens Nerve in the Lateral Rectus Muscle for the Management of Strabismus

Abstract

Sihler's staining is a useful technique for visualizing the entire nerve network of the LR. Improving the knowledge of the nerve distribution patterns is important not only for researchers but also clinicians to understand the functions of the LR and the diverse pathophysiology of strabismus.

Intramuscular innervation of the lateral rectus muscle evaluated using sihler's staining technique: Potential application to strabismus surgery

“…Skeletal muscles are not monolithic structures (Peng et al, ), and may contain neuromuscular compartments or functional zones that are responsible for different biomechanical functions (Demer et al, ; Oh et al, ; Mu and Sanders, ; Holtermann et al, ; Peng et al, ; Demer et al, 2011; Clark and Demer, ; Demer and Clark, ; Shin et al, , ). English et al () proposed a hypothesis with respect to muscles' compartmentalization that he referred to as “the partitioning hypothesis.” This hypothesis is based on the fact that neurovascular compartments “[…] are distinct subvolumes of a muscle, each innervated by an individual muscle nerve branch and each containing motor unit territories with a unique array of physiological attributes” (p. 857).…”

“…For example, differential compartmental activity in the lateral rectus is suggested during convergence (Demer and Clark, ). The detailed knowledge of structure and function of the lateral rectus muscle may also be crucial during the surgical correction of strabismus (Shin et al, ).…”

“…Shin et al () applied Sihler's stain to elucidate the abducens nerve's intramuscular distribution in the lateral rectus muscle. Their findings were consistent with our results.…”

“…To visualize the abducens nerve's intramuscular distribution of subbranches, the isolated lateral rectus muscles were stained using Sihler's whole mount nerve staining technique using the procedure Mu and Sanders () described, which allowed the detailed lateral rectus intramuscular innervation pattern to be evaluated. Based on our earlier experience and on the current literature, the procedure was modified for a small muscle mass (Wysiadecki et al, , Shin et al, , ). The initial phase of Sihler's Stain (i.e., maceration and depigmentation) requires 3 to 5 weeks.…”

“…Moreover, different neuromuscular compartments within a single muscle may serve different biomechanical functions (Demer et al, ; Oh et al, ; Peng et al, ; Demer et al, ; Shin et al, , ). Theoretically, the characteristic intramuscular distribution of the nerve subbranches within the horizontal rectus extraocular muscles allows selective activation of specific areas (zones) that control specific movements or phases of movement (Goldberg et al, , ; Demer et al, ; Oh et al, ; Guthrie, ; Peng et al, ; Demer et al, 2011; Clark and Demer, ; Demer and Clark, ; Shin et al, , ). To take a specific example, although the main function of the lateral rectus muscle's is abduction of the eyeball, some data point to differential lateral rectus compartmental contraction during the vestibulo–ocular reflex (Clark and Demer, ), as well as during conjugate and converged ocular adduction (Demer and Clark, ).…”