Download 1 Configuration of the Connective Tissue in the Posterior Atlanto

1
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 atlantooccipital membrane, nuchal ligament, and the spinal dura in the posterior atlantooccipital 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.
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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.”
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“Microstrain and trauma in the rectus capitis posterior minor muscle and its
tendon may cause a clonous condition of the muscle and stimulate the painsensitive 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.
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3)
This study clearly demonstrates that the rectus capitis posterior minor
tendon fibers are directly continuous with the spinal dura via the posterior atlantooccipital 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 craniocervical 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.