Internal structure and topography
Spinal cord anatomy is based on a clear distinction between gray and white matter. Gray matter is located centrally and resembles a butterfly on transverse sections. The optimal method for evaluating this structure is magnetic resonance imaging (MRI) in T2-weighted sequences.
Caudally, the spinal cord tapers to form the conus medullaris (conus medullaris). Normally, it is located at the level of the first and second lumbar vertebrae (L1–L2). Below this level, the vertebral canal contains only descending nerve roots, which form the cauda equina (cauda equina).
Spinal nerves exit the spinal canal through the intervertebral foramina (neuroforamina). Their exit trajectory varies:
- In the cervical and thoracic segments, the roots run laterally in a horizontal direction.
- In the lumbar region, the roots first descend inferiorly within the lateral recess, and only then exit through the foramen.
Arterial blood supply and venous drainage
The blood supply to the spinal cord is provided by three longitudinal major arteries: one anterior and two posterior. Physiologically, three arterial supply zones are distinguished:
- Cervicothoracic zone: supplied segmentally by the vertebral arteries, as well as neck vessels (branches of the aorta, carotid and subclavian arteries).
- Mid-thoracic zone: this is the watershed area. It receives blood from the collateral network of superior and inferior basins, as well as from small perforating branches of the aorta.
- Thoracolumbar zone: supplied by large segmental arteries branching from the aorta and iliac vessels.
The largest vessel supplying the lower segments is the artery of Adamkiewicz (artery of Adamkiewicz). Blood outflow occurs into the Batson plexus (Batson plexus), a unique venous system completely devoid of valves.
Craniocervical junction (CCJ)
The craniocervical junction is a complex biomechanical complex connecting the spherical skull to the tubular spine. The muscles of this area initiate movements rather than limit them—bones and ligaments are responsible for stability.
Bony framework includes the occipital bone, the atlas (C1) with its lateral masses and arches, and the axis (C2), which features a specific odontoid process (dens). The dens of the axis forms a joint with the anterior arch of the atlas.
Ligamentous apparatus is divided into two groups:
- External ligaments: anterior longitudinal ligament (ALL), ligamenta flava (ligamenta flava), and ligamentum nuchae (ligamentum nuchae).
- Internal ligaments: thick alar ligaments (alar ligaments) attaching the dens to the foramen magnum, and the cruciform ligament. The most critical element of the latter is the transverse ligament (transverse ligament). It fixes the dens of the axis to the anterior arch of the atlas and is the thickest ligament of the craniocervical junction. Posteriorly, the complex is covered by the tectorial membrane (tectorial membrane), which continues as the posterior longitudinal ligament.
Diagnostic radiology
Choice of modality depends on the clinical situation and age:
- MRI: The gold standard for non-traumatic lesions. The main advantage is the absence of ionizing radiation, excellent visualization of the spinal cord, bone marrow, and ligaments.
- CT: The modality of choice in acute blunt trauma. CT is indicated for unexplained neurological deficit, local pain, or unclear findings on radiographs. It demonstrates bone anatomy and degenerative changes in the elderly exceptionally well.
- Radiography: Used primarily in minor trauma as a baseline screening tool.
Briefly: answers to topical questions
What anatomical structures pass through the intervertebral foramina (neuroforamina)?
Spinal nerves exit the vertebral canal through the intervertebral foramina (neuroforamina). In the cervical and thoracic regions, the roots exit horizontally. In the lumbar region, the roots first descend downward within the lateral recess (lateral recess) and then exit through the foramen.
Which spinal cord and vertebral structures are optimally visualized on T1-weighted MRI?
T1-weighted MRI evaluates normal bone marrow signal distribution patterns within vertebral bodies, including the detection of a uniform low-intensity signal with a linear high-intensity signal surrounding the basivertebral vein, band-like hyperintense signals, and large hyperintense foci. Contrast-enhanced T1-weighted imaging is also used to visualize focal contrast enhancement in the spinal cord lesion area.
At the level of which vertebrae are the cervical and lumbosacral enlargements of the spinal cord located?
The provided study guides do not contain information on the exact anatomical level of the cervical and lumbosacral spinal cord enlargements (only the terminal end of the spinal cord—the conus medullaris, normally located at the L1–L2 level—is mentioned).
To easily remember the blood supply characteristics: the cervical zone has a rich blood supply (from major vessels), the mid-thoracic zone is a sparse "watershed" (risk of ischemia), and the thoracolumbar zone has a powerful reserve in the form of the artery of Adamkiewicz.
Class and exam questions
At what level does the spinal cord terminate?
Normally, the terminal end of the spinal cord, or conus medullaris, is located at the level of the L1–L2 vertebrae.
What is the characteristic feature of the spinal venous system?
Batson's plexus has no venous valves. This means that an increase in pressure can cause retrograde blood flow.
What imaging modality should be chosen first in severe spinal trauma?
In blunt spinal trauma, computed tomography (CT) is the preferred initial method as it details bone structures in any plane.
Which ligament is the primary stabilizer of the C2 dens?
The transverse ligament of the atlas. It runs posterior to the odontoid process and firmly holds it against the anterior arch of C1.
What else to study on this topic
- Detailed MRI anatomy of facet and uncinate joints
- Spinal ligamentous apparatus: ALL, PLL, and ligamenta flava
- Imaging selection criteria for low back pain (LBP)
- Age-related changes in vertebral body bone marrow MR signal
- Harborview criteria for high-risk cervical spine injury
Master the entire topic in the "Diagnostic Radiology" course
This is a summary. The course covers everything tested in classes and exams.
- Comprehensive study guide on the "Spinal cord" and 2,199 more pages of the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 10 video lessons on the subject
Other topics in the "Spine" section
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.