Rectus capitis posterior minor and its relationship to the spinal dura mater: a histological investigation (913.3)

Abstract

The rectus capitis posterior minor (RCPm) is a deep suboccipital muscle connecting the tubercule of the posterior arch of the atlas to the inferior nuchal line of the occipital bone. Although controversial, a number of dissection‐based or imaging‐based reports suggested a direct connection between the RCPm and the dura mater. Detailed histologic investigation is required to establish any link between RCPm and the dura mater.Left and right RCPms, their bony attachments and adjacent spinal dura mater, were resected from 6 embalmed and 2 unfixed cadavers. Tissue samples were fixed with 4% paraformaldehyde in phosphate buffered saline and decalcified. Both left and right RCPms were subdivided into medial and lateral parts and processed for histological examination. Serial histological sections were prepared in order to include maximum surface area; Masson’s trichrome stain was used to visualize muscle and connective tissue connections.Histological analysis suggested an indirect link between RCPm and the dura mater. This investigation also found tissue distributions previously unreported, i.e.: periosteum of the occipital bone blends into the spinal dura mater on the medial aspect; tissue between the RCPm and dura mater has a structural organisation similar to a bursa or fat pad and this structure is reinforced by traversing collagen bundles taking origin at the peri‐ and/or endomysium of the RCPm.This histological investigation clarifies some anatomical features of the suboccipital region and indicates a secondary function of the RCPm, which may include posterior traction of the dura mater during neck hyperextension.Grant Funding Source: Natural Sciences and Engineering Research Council of Canada (NSERC)