Determination of motor entry points of musculus splenius capitis

Determination of Motor Entry Points of Musculus Splenius Capitis Aim: For the treatment of various disorders characterized by spasm and pain in the neck and its surroundings, the motor entry points of the muscles in the region are necessary for treatment to be performed more effectively, accurately and easily. Musculus splenius capitis (MSC) is one of the most affected muscles for the neck disorders such as cervical dystonia and whiplash injuries, is often treated with injection of Botulinum Toxin (BT). In these procedures, it is necessary to know MSC's motor entry points in order to reduce the side effects of the drug, to make the application easier and not to damage the surrounding structures. The aim of this cadaver study was to determine the target sites for m. splenius capitis for the injection of agents involved in the treatment of various disorders associated with spasm of the neck muscles. Methods: The posterior neck regions of 10 adult human cadavers (20 sides in total), which fixed in 10% formalin solution and were recorded in the inventory of Ege University Faculty of Medicine Department of Anatomy and obtained in accordance with the relevant laws for educational and research purposes, were examined. After dissection, anatomical guide points were determined and the distances between them were measured. The depth and thickness of the MSC were measured in the cadavers with skin. Motor entry points (MEP) of the nerves entering the musculus splenius capitis were detected and marked. The distance of the motor entry points to the anatomical guide points was measured and recorded. Results: After dissections, in six cadavers two MEPs for both right and left side, in two cadavers three MEPs for both right and left side, in one cadaver one MEP for both right and left side, and in one cadaver three MEP for the right side and one MEP for the left side were found. The mean distances between the processus mastoideus and protuberentia occipitalis externa (X-axis) were 88.05 mm (±8.33mm) on the right side and 88.91 mm (±7.35mm) on the left side. The mean distance between protuberentia occipitalis externa and processus spinosus of vertebra prominens (Y-axis) was 127,77 mm (±15,41mm). The thickness of the skin, subcutaneous tissue and m. trapezius was found to be 12.16 mm (± 2.04 mm) in the nape of five intact cadavers. The mean thickness of musculus splenius capitis was 2.58 mm (± 0.76 mm). The first MGN's, which are the closest to the X-axis, mean distance to the X-axis was found to be 46, 41 mm (± 10.48 mm), and the mean distance to the Y axis was 40.87 mm (± 10.26 mm). The mean distance to the X-axis of the 3rd MGNs, which is the most distant MGN to the X axis, was 56.28 mm (± 12.44 mm) and the mean distance to the Y axis was 33.72 mm (± 9.21 mm). Conclusion: In this study, anatomical guide points and motor entry points were determined for injection applications to MSC. We believe that the data we have obtained will help clinicians who will practice in this region to act more accurately and safely and will guide other studies in this area. Key Words: m. splenius capitis; botulinum toxin; motor entry point; injection applications; cervical dystonia; anatomical guide points.