The structure of dural attachments in the craniocervical region is a topic of considerable importance to chiropractic. The dense connective tissue bridge between the rectus capitus posterior minor muscle and the dura has been noted to resist dural infolding toward the spinal cord. Dural traction has been posited as a possible mechanism in cervicogenic headache. In the present study, the location and extent of myodural attachments from the rectus capitis posterior minor muscle to the posterior spinal dura is examined in 16 cadaver specimens, as the first stage in a study which will later include histological and ultrastructural analysis.

METHODS: The sample consisted of 16 embalmed cadaver specimens, obtained from the gross anatomy laboratory of Palmer College of Chiropractic. Each specimen was dissected to expose the suboccipital triangle. The three superficial suboccipital muscles were then carefully removed, preserving the rectus capitis posterior minor muscle intact. Each specimen was future sectioned using a band saw, to produce a 2 inch wide block, which preserved the rectus capitus posterior minor in its entirety on each side. A dental saw was then used to make a midsagittal cut, extending form between the insertion of the left and right recuts capitus posterior minor at occiput, through the center of the specimen for each individual. Each specimen block was then further dissected, to fully reveal the origin and insertion of the rectus capitus posterior minor. All specimens were photographed under an Olympus dissecting microscope.

RESULTS: A unilateral attachment fro the rectus capitus posterior minor to the dura with no other dural attachments was identified in 11 individuals. A bilateral attachment form the rectus capitus posterior minor to the dura was found in two individuals. In one individual, the only attachment was found between the inferior border of the posterior arch of the atlas and the dura unilaterally. In two individuals, an attachment fro the rectus capitus posterior minor to the dura was present unilaterally, while an attachment form the posterior arch of the atlas to the dura was present contralaterally. The man length of the attachment from the rectus capitus posterior minor to the dura was 13.6 mm, with a standard deviation (SD) of 2.67mm. The mean width was 1.2 (SD=0.55)mm. The mean length attachments from the posterior arch of the atlas to the dura was 8.8 (SD+1.52) mm, while the mean width was 2.7 (SD=0.38) mm. IN males, the mean length and width of the rectus capitus posterior minor dural attachment were 13.3 (SD=3.41) mm and 0.9 (SD=0.48) mm, respectively, while in females the mean length was 13.2 (SD=2.29) mm and the mean width was 1.0 (SD=0.31)mm.

DISCUSSION: The results of the descriptive study indicate considerable variation in the length , width, and location of attachments to the dura at the craniocervical junction. Vertebral misalignment in the upper cervical region may place traction on the nerve-rich dura via these attachments. It is particularly during flexion that maximal traction would be placed on the dura, as flexion opens the space between the occiput and atlas. It may be hypothesized that short and /or bilaterally asymmetrical connective tissue attachment to the dura may produce increased traction, increasing the risk of cervicogenic headache. Histological factors are also likely to play a role. Future studies will focus on the histological composition and ultrastructural characteristics of these dural attachments.

CONCLUSION: Connective tissue attachments from the rectus capitus posterior minor to the dura show considerable variation both within individuals (bilateral asymmetry) and between individuals. Such variations may have clinical relevance with regard to cervicogenic headache.