Branching patterns of rabbit oculomotor and trochlear nerves demonstrated by Sihler's stain technique

Comparison of the Superior and Inferior Rectus Muscles in Humans: An Anatomical Study with Notes on Morphology, Anatomical Variations, and Intramuscular Innervation Patterns

A comparison of the superior and inferior rectus muscles was performed to determine whether they have similar structures and innervation attributable to their participation in the same type of, although antagonistic, eye movements. The study was conducted on 70 cadaveric hemiheads, and the anatomical variations in the superior and inferior rectus muscles were assessed. Sihler's whole mount nerve staining technique was used on 20 isolated superior and 20 isolated inferior rectus muscle specimens to visualize the intramuscular distribution of the oculomotor nerve subbranches. In two cases (~2.8%), variant muscular slips were found that connected the superior and inferior rectus muscles. In 80% of cases, muscular branches arising directly from the inferior branch of the oculomotor nerve innervated the inferior rectus muscle, while in 20% of cases, the nerve to the inferior oblique muscle pierced the inferior rectus muscle and provided its innervation. In 15 of 70 specimens (21.4%), a branch to the levator palpebrae superioris muscle pierced the superior rectus muscle. The distance between the specific rectus muscle's insertion and the anterior-most terminations of the nerves' subbranches with reference to the muscle's total length ranged from 26.9% to 47.2% for the inferior rectus and from 34.8% to 46.6% for the superior rectus, respectively. The superior rectus muscle is slightly longer and its insertion is farther from the limbus of the cornea than is the inferior rectus muscle. Both muscles share a common general pattern of intramuscular nerve subbranches' arborization, with characteristic Y-shaped ramifications that form the terminal nerve plexus located near half of the muscles' length. Unexpected anatomical variations of the extraocular muscles may be relevant during orbital imaging or surgical procedures.

Comparison of lateral and medial rectus muscle in human: an anatomical study with particular emphasis on morphology, intramuscular innervation pattern variations and discussion on clinical significance

This paper aims to present various aspects of the anatomy of horizontal (i.e., lateral and medial) rectus muscles. It mainly compares morphology and detailed patterns of intramuscular innervation of those muscles. It is also one of the first reports that uses the Sihler's stain to examine human extraocular muscles. The study was conducted on 80 isolated cadaveric hemi-heads. Sihler technique of nerves staining served to expose the course of intramuscular branches of the oculomotor and abducens nerves. The lateral rectus was longer (48 mm versus 46.5 mm) and more distant from the limbus (6.8 mm versus 5.7 mm) than the medial rectus muscle. Three variants of the abducens nerve primary division were observed in the lateral rectus muscle. In the medial rectus muscle, the motor branch from the oculomotor nerve was more evenly divided into sub-branches. In both examined horizontal rectus muscles, primary muscular branches split into secondary sub-branches, which undergo numerous further divisions. The most numerous terminal sub-branches formed the terminal plexus. The distance between the insertion and the anterior-most end of the terminal plexus referenced to the total length of the muscle ranged from 35.4 to 48.5% for the lateral rectus muscle and from 36.3 to 50.5% for medial rectus muscle. Both horizontal rectus muscles share similar general pattern of distribution of intramuscular nerves, with characteristic root-like arborizations of sub-branches. The terminal nerve plexus was observed near half of both muscles' length. Knowledge of variations and innervation pattern of the extraocular muscles may be relevant during ophthalmology surgeries.

Sihler's whole mount nerve staining technique: a review

Sihler's stain is a whole mount nerve staining technique that renders other soft tissue translucent or transparent while staining the nerves. It permits mapping of entire nerve supply patterns of organs, skeletal muscles, mucosa, skin, and other structures after the specimens are fixed in neutralized formalin, macerated in potassium hydroxide, decalcified in acetic acid, stained in Ehrlich's hematoxylin, destained in acetic acid, and cleared in glycerin. The unique advantage of Sihler's stain over other anatomical methods is that all the nerves within the stained specimen can be visualized in their three-dimensional positions. To date, Sihler's stain is the best tool for demonstrating the precise intramuscular branching and distribution patterns of skeletal muscles, which are important not only for anatomists, but also for physiologists and clinicians. Advanced knowledge of the neural structures within mammalian skeletal muscles is critical for understanding muscle functions, performing electrophysiological experiments and developing novel neurosurgical techniques. In this review, Sihler's stain is described in detail and its use in nerve mapping is surveyed. Special emphasis is placed on staining procedures and troubleshooting, strengths and limitations, applications, major contributions to neuroscience, physiological and clinical significance, and areas for further technical improvement that deserve future research.

Innervation of the rat anterior abdominal wall as shown by modified Sihler's stain

OBJECTIVE

The purpose of this study was to use the modified Sihler's staining technique to demonstrate detailed distribution of the rat anterior abdominal wall nerves and test the value of Sihler's technique in demonstrating such a complex muscle-nerve relationship.

MATERIALS AND METHODS

The anterior abdominal walls of 5 Wistar rats were isolated by making a deep incision from the costal arches on each side down to the inguinal region and processed using a modified Sihler's stain technique.

RESULTS

This technique was successfully applied to visualize the innervation of the anterior abdominal wall muscles of the rat. The segmental nerves of T6-L1 and their terminal branches were shown and possible motor and sensory fibers identified.

CONCLUSIONS

This technique is valuable in understanding the complex nature of final branching of the nerve endings, and it may be useful for studying experimental nerve models.