Morphometric characteristics and variations of the suboccipital muscles: A cadaveric study

Background

The suboccipital muscle complex critically contributes to upper cervical biomechanics and proprioceptive regulation of head posture; however, the comprehensive morphometric characterization and prevalence of its anatomical variants remain poorly defined.

Objectives

This study aimed to evaluate the morphometric characteristics and variations of the suboccipital muscles, assess their symmetry, and determine prevalence of anatomical variations with potential clinical significance.

Design

A cross-sectional cadaveric study.

Method

This study was conducted on 27 cadaveric heads preserved in formalin-alcohol-phenol solution. The suboccipital muscles were dissected to expose the anatomical structures. Morphometric measurements were performed using a digital caliper. Symmetry between the left and right sides was analyzed for each muscle. The presence of anatomical variations such as bifid structures, accessory fibers, and atlantomastoid muscles was recorded.

Results

Bilateral variations in RCPmi were observed in 11.11 % of the cadavers, while a unilateral variation in OCi was identified in 3.7 % of cases. The atlantomastoid muscle was present in 11.11 % of the specimens. No significant differences were observed in the morphometric data of the muscles on the right and left sides; all were symmetrical. No variations were observed in OCs.

Conclusions

This study provides essential anatomical insights into the prevalence of suboccipital muscle variations, particularly in RCPmi and RCPma, which could influence clinical procedures such as dry needling and electromyography (EMG). The findings emphasize the importance of anatomical knowledge in preventing procedural complications. Future studies with larger sample sizes and functional analyses are needed to further explore the clinical impact of these variations.