Headaches and Dura Tissue Matter

Configuration of the Connective Tissue in the Posterior Atlanto-Occipital Interspace Spine Volume 30(12) June 15, 2005 pp 1359-1366 Nash, Lance MSc; Nicholson, Helen MB, PhD; Lee, Antonio S. J. MSc; Johnson, Gillian M. PhD; Zhang, Ming MB, MMed, PhD

FROM ABSTRACT:
Study Design.
The connective tissue structures in the posterior atlanto-occipital region were investigated.
Objectives.
To define the relationship between rectus capitis posterior minor, posterior atlanto-occipital membrane, nuchal ligament, and the spinal dura in the posterior atlanto-occipital interspace.
Summary of Background Data.
It has been speculated that connections between the dura and muscles and/or ligaments in the posterior atlanto-occipital interspace may transmit forces from the cervical spine joint complexes to the pain-sensitive dura, generating cervicogenic headaches.
Anatomic structures involved in these connections include the rectus capitis posterior minor, posterior atlanto-occipital membrane, and nuchal ligament.

Results.
The study demonstrates that:
1) The tendinous fibers from the medial and deep part of the rectus capitis posterior minor muscle are continuous antero-inferiorly with the spinal dura.
2) The posterior atlanto-occipital membrane is part of the rectus capitis posterior minor fascia and tendon and the perivascular sheathes.
3) Antero-inferiorly the posterior atlanto-occipital membrane fuses with the spinal dura rather than the atlas.
4) The nuchal ligament does not exist in the posterior atlanto-occipital interspace.

Conclusions.
The connective tissue structures that connect the spinal dura to the rectus capitis posterior minor muscle in the posterior atlanto-occipital interspace are the rectus capitis posterior minor fascia and tendinous fibers and perivascular sheathes.

THESE AUTHORS ALSO NOTE:
"Recently, the spinal dural connection of the rectus capitis posterior minor muscle and the nuchal ligament in the posterior atlanto-occipital interspace has been reported extensively." [8 references]
"Speculation exists that dura-muscular and dura-ligamentous connections transmit forces from the cervical spine joint complexes to the pain-sensitive spinal dura and may contribute to the pathologic development of cervicogenic headaches."
"The posterior atlanto-occipital membrane, extending between the posterior arch of the atlas (C1) and the occiput, has been observed to tether the spinal dura by numerous connective tissue fibers creating a posterior atlanto-occipital membrane-spinal dura complex."
Twenty-two human adult cadavers were used in this study.

RESULTS:
The tendinous fibers of the rectus capitis posterior minor muscle fuse with the spinal dura via the posterior atlanto-occipital interspace.
This study clearly demonstrates that the rectus capitis posterior minor tendon fibers are directly continuous with the spinal dura via the posterior atlanto-occipital interspace and become a part of the spinal dura.
The posterior atlanto-occipital membrane is formed by the rectus capitis posterior minor fascia and vertebral vascular sheath and fuses with the spinal dura.
"No direct continuity between the nuchal ligament and the posterior cervical dura mater at the posterior atlanto-occipital interspace was found in this study."

DISCUSSION:
"The tendon of the rectus capitis posterior minor directly attaches to the spinal dura via the posterior atlanto-occipital interspace."
"The present study demonstrates, for the first time, that tendinous fibers of the rectus capitis posterior minor muscle are continuous with the spinal dura."
"A direct continuity of the rectus capitis posterior minor muscle to the spinal dura should have a great impact on strengthening the dura and preventing dural enfolding. Such an impact becomes particularly important during extension of the head and neck because, when the rectus capitis posterior minor muscle extends the cranio-cervical junction, a small portion of its muscular fibers simultaneously contract to pull the spinal dura posteriorly, preventing dural enfolding."
"Microstrain and trauma in the rectus capitis posterior minor muscle and its tendon may cause a clonous condition of the muscle and stimulate the pain-sensitive dura, generating a cervicogenic headache."
These authors conclude that the posterior atlanto-occipital membrane is mainly formed by the rectus capitis posterior minor tendinous fibers, the deep layer of the rectus capitis posterior minor fascia, and perivascular connective tissue sheathes.
These authors believe that the rectus capitis posterior minor tendon and fascia have historically been misrepresented as being the posterior atlanto-occipital membrane.
These authors also note that since the posterior atlanto-occipital membrane really does not exist, that there is no real ligamentous structure existing at the posterior cranio-cervical junction.
Rather, these authors suggest that as the rectus capitis posterior minor fascia is the main connective tissue structure in the posterior atlanto-occipital interspace, and that the rectus capitis posterior minor fascia and muscle are the main contributors to posterior cranio-cervical stability.
"The morphologic features of the rectus capitis posterior minor tendon and fascia indicate that they may have an important role in the maintenance of the posterior cranio-cervical stability and the prevention of the dural enfolding and are of anatomic relevance in the debate regarding the etiology of cervicogenic headaches."

KEY POINTS FROM AUTHORS:
1) The rectus capitis posterior minor tendon fuses with the spinal dura.
2) The rectus capitis posterior minor tendinous fibers, fascia and the perivascular sheathes form the posterior atlanto-occipital membrane.
3) The posterior atlanto-occipital membrane fuses with the spinal dura.
4) The nuchal ligament does not attach to the spinal dura.

KEY POINTS FROM DAN MURPHY:
1) Connections between the spinal dura and muscles / ligaments in the posterior atlanto-occipital interspace may transmit forces from cervical spine joints to the pain-sensitive dura, generating cervicogenic headaches.
2) The tendinous fibers of the rectus capitis posterior minor muscle fuse with the spinal dura via the posterior atlanto-occipital interspace.
3) This study clearly demonstrates that the rectus capitis posterior minor tendon fibers are directly continuous with the spinal dura via the posterior atlanto-occipital interspace and become a part of the spinal dura.
4) The direct continuity of the rectus capitis posterior minor muscle to the spinal dura prevents dural enfolding and injury during extension of the head and neck.
5) When the rectus capitis posterior minor muscle extends the cranio-cervical junction, a small portion of its muscular fibers simultaneously contract to pull the spinal dura posteriorly, preventing dural enfolding and dural injury.
6) Static strain and/or trauma to the rectus capitis posterior minor muscle may stimulate the pain-sensitive dura, generating a cervicogenic headache.
7) The rectus capitis posterior minor fascia is the main connective tissue structure in the posterior atlanto-occipital interspace, and that the rectus capitis posterior minor fascia and muscle are the main contributors to posterior cranio-cervical stability.

CLINICAL APPLICATION FROM DAN MURPHY:
[Hack GD, Koritzer RT, Robinson WL, et al. Anatomic relation between the rectus capitis posterior minor muscle and the dura mater. Spine 1995;20:2484-6.]
The original study by Hack (above) documenting a connection between the rectus capitis posterior minor muscle and the spinal dura mater through a connective tissue bridge was published in 1995, and at that time I proposed the following:

1) The spinal dura is innervated with pain afferents.
2) Contraction of the rectus capitis posterior minor pulls the spinal dura into a safe position so that is does not enfold into the spinal cord causing cord injury or injury to the dura itself.
3) Whiplash extension injuries occur so quickly (taking less than .1 seconds) that the rectus capitis posterior minor muscle does not have enough time (requiring about .2 seconds) to contract and pull the spinal dura to safety.
4) The resulting injury to the pain sensitive dura could be a cause of post whiplash headache.

This study supports this model.

This study also supports the contention that chronic upper neck postural stress and distortions can cause chronic stress on the spinal dura mater.