Anatomy and clinical relevance of sub occipital soft tissue connections with the dura mater in the upper cervical spine

Abstract

Background: The upper cervical region is a complex anatomical structure. Myodural bridges between posterior suboccipital muscles and the dura might be important explaining conditions associated with the upper cervical spine dysfunction such as cervicogenic headache. This cadaver study explored the upper cervical spine and evaluated the myodural bridges along with position of spinal cord in response to passive motion of upper cervical spine.

Methods: A total of seven adult cadavers were used in this exploratory study. The suboccipital muscles and nuchal ligament were exposed. Connections between the Rectus Capitis Posterior major/minor and the Obliquus Capitis minor, the nuchal ligament, posterior aspect of the cervical spine, flavum ligament and the dura were explored and confirmed with histology. The position of the spinal cord was evaluated with passive motions of the upper cervical spine.

Outcomes: In all cadavers connective tissues attaching the Rectus Capitis Posterior Major to the posterior atlanto-occipital membrane were identified. In the sagittal dissection we observed connection between the nuchal ligament and the dura. Histology revealed that the connection is collagenous in nature. The spinal cord moves within the spinal canal during passive movement.

Discussion: The presence of tissue connections between ligament, bone and muscles in the suboccipital region was confirmed. The nuchal ligament was continuous with the menigiovertebral ligament and the dura. Passive upper cervical motion results in spinal cord motion within the canal and possible tensioning of nerve and ligamentous connections.

Keywords: Cervical spine; Dissection; Myodural bridge; Nuchal ligament.

Figure 1. Posterior dura connection to posterior arch of C1.

Posterior dura (D) connection to posterior arch of C1 (C1). Red arrows point to the connection between dura and the posterior longitudinal ligament (Pl).

Figure 2. The nuchal ligament in the midsagittal plane and its orientation relative to the upper cervical spine.

Red arrows indicate the ligament relative to the occipital bone (o), posterior arch of atlas (PA), spinous process C2 (C2) and C3 (C3).

Figure 3. Exploration the suboccipital region.

The trapezius (T) and Splenius Capitis (SC) have been removed. The Nuchal ligament (NL) is exposed and the Rectus Capitis Major (RcMa), Rectus Capitis Minor (RcMi) and Obliquus Capitis Inferior (OCi) can be seen.

Figure 4. Meningovertebral fuzz.

The red arrow identifies the tissue “Fuzz” (F) between posterior side transverse ligament (TL) and anterior aspect dura (D).

Figure 5. The myodural bridge.

The myodural bridge (myB) is identified by the red arrows and spans over the posterior arch of C1 (PA) (right side identified) toward the dura (D).

Figure 6. Nuchal ligament dural connection.

Nuchal ligament (NL) with connection to atlas (A), spinous process C2 (C2), C3 (C3) and C4 (C4). Tensioning the nuchal line creates tension on dura (red arrows).

Figure 7. Nuchal-dural connection.

Stained tissue slide demonstrating the presence of collagen fibers (blue) connecting the nuchal ligament with the meningovertebral ligament and blending with the dura.

Figure 8. Deflection of spinal cord upon flexion and extension C1 on C2.

In both images (A) signifies the anterior and P posterior aspect of the spine. Image (A) demonstrates the forward movement of the spinal cord (SC) during extension. The white arrows demonstrate the distance between anterior cord and posterior vertebral arch. Image (B) demonstrates a posterior deflection of the cord during flexion. The white arrows demonstrate the distance between anterior cord and posterior vertebral arch.

Figure 9. Deflection of spinal cord upon rotation C1 on C2.

Image (A) demonstrates the movement of the spinal cord (SC) to the right during right rotation (red arrows demonstrate movement) relative to C1 (C1). The white arrow shows that the left spinal nerves appear tight during this motion. Image (B) demonstrates a left deflection of the cord during left rotation of C1 and there appears tightening of the right spinal nerves.