An initial evaluation of the spine-whether cervical, thoracic, and/or lumbar-typically starts with review of sagittal images. For the cervical spine, key sagittal images include a midline image and off-midline images at the level of the atlanto-occipital (C0-C1) and atlanto-axial (C1-C2) joints.

The simple act of establishing vertebral enumeration is one of the more important tasks performed in spine radiology (and clinical practice). The cervical spine nearly always has 7 vertebrae. The rare exceptions include uncommon conditions associated with segmentation anomalies such as Klippel-Feil syndrome. More commonly, cervical ribs may occur at C7, but this should not affect enumeration. In contrast, the thoracic and lumbar spine have frequent variations in numbers of vertebrae or transitional vertebrae.

For these reasons, consistent designation of vertebral body enumeration is best accomplished by counting 'top down,' beginning at C1. However, if imaging of the cervical spine is not available, it is reasonable to assume there are probably 7 cervical vertebrae.

In sum the key concepts are: start with the midline sagittal images, establish enumeration by counting top down, and the cervical spine nearly always has 7 vertebrae.

CVJ. atlantodental interval.....Joints for trauma or setting of pain/degenerative change of C1-2 joint-an important cause of cervicogenic headache... Note that with head turning, the C1-2 joints may be offset..

C1 is the only vertebrae without a vertebral body or an intervertebral disc. It consists of an anterior and posterior arch, lateral masses, and transverse processes. The C2 pedicles are directed in an antero-posterior direction whereas the pedicles of C3-C7 are obliquely oriented (not visualized here). The lateral C1-C2 joints have an inferolateral slant. The C2-C3 joints have a slight superolateral slant. The transverse processes of T1 (greyed out) are larger than those of the cervical spine and have a superolateral orientation.

This image allows assessment of general alignment (red lines), normal cervical lordosis, and vertebral body height. Several key measurements of the craniocervical junction and upper cervical spine can be make, including the anterior atlanto-dental interval (ADI) (yellow) which may be abnormal with loss of integrity of the transverse ligament, and basion-dens interval (BDI) (blue arrow) which may be widened (> 10 mm) with atlanto-occipital dissociation or narrowed with basilar invagination or impression. The basion and opisthion at the anterior and posterior margins of the midline foramen magnum respectively are important landmarks of the craniocervical junction. Disc height and evaluation for normal alignment (orange) versus splaying of the spinous processes is also possible.

This view is valuable for assessment of several additional key structures of the craniocervical junction as well as the subaxial facet joints of the cervical spine. It is often one of the first images assessed during interpretation of cervical spine imaging examinations. The occipital condyle should be well-seated within the C0-C1 joint (or 'yes' joint), allowing head nodding). The C1-C2 joint differs from the subaxial cervical facet joints; it is nearly horizontal (with a slight centrally convex curve) and anteriorly located (or 'no' joint, allowing head rotation). The cervical facet joints should all be well-aligned like shingles on a roof.

Sagittal CT of the soft tissues of the cervical spine. Several key ligaments of the CCJ can be seen, in particular the tectorial membrane, apical ligament, and anterior atlanto-occipital membrane. The spinal cord can be differentiated from lower density CSF (although beam-hardening artifact often limits the evaluation of the caudal cervical spinal canal).

Dorsal epidural fat is very scant above the C6-C7 level. Interlaminar epidural injections of the cervical spine are preferably performed at C7-T1 (if epidural fat is identified on pre-procedure imaging) and recommended to be performed no higher than C6-C7 .

The nuchal ligament from C7 to occiput is an extension of the supraspinous ligament.

The tectorial membrane is an extension of the posterior longitudinal ligament.

Key coronal image of the cervical spine. Note that the occipital condyle, a relatively common location for fractures, is well visualized. The C0-C1 joints have a superolateral slant whereas the C1-C2 joints have an inferolateral slant, giving the C1 lateral mass a wedge-shape. Because of this slant, the C1-C2 joint is not well seen on a true lateral radiograph or fluoroscopic image (although lateral images are recommended during C1-C2 joint injections to confirm optimal depth of needle placement). The odontoid process, another common location for fracture, is also well-assessed.

There are many critical structures near the C1-2 joint which are important for clinical scenarios such as planning a joint injection. These include the C2 ganglion (posterior), vertebral artery (lateral), spinal canal (medial), and internal carotid artery (anterior).

While the CVJ (sometimes referred to as the Cranial Cervical Junction-CCJ) was introduced in a previous section, the main ligaments as well as the C0-C1 and C1-C2 joints are included here.

Alar, apical, tectorial membrane, cruciate provide support.

Apical cave.

poserior atlanto-occipital

Reference

Riascos R, et al. Imaging of atlanto-occipital and atlantoaxial traumatic injuries: what radiologists need to know. Radiographics 2015;35(7):

The osseous anatomy of the cervical spine can be simplified by recognizing that C1, C2, and C7 vertebrae are unique while C3-C6 have similar anatomy. C1 is a ring with anterior and posterior arches, lateral masses, and transverse processes. However, C1 is the only vertebrae to lack a vertebral body and an associated intervertebral body disc. The tubercles for transverse ligament attachment are important to assess in the setting of a Jefferson fracture as are the relative positions/overhang of the lateral masses relative to those of C2. Additionally, the C0-C1 and C1-C2 articulations are unique.

The C2 vertebral body has unique development and shape. The pedicles are directed in the AP plane, whereas the pedicles of C3-C7 are more obliquely oriented (and hence often true pedicle screws are placed in C2 and 'lateral mass' screws in C3-C7 with posterior instrumented fixation. The C2-C3 facet joints have a slightly different orientation relative to the remaining facet joints.

The shape of the C2 vertebrae is unique and can be identified on a single axial image. The pedicles are more prominent than at other cervical levels and are directed in the AP plane (rather than obliquely). This is important surgically as 'pedicle screws' may be placed at C2 whereas 'lateral mass' screws are more commonly placed in the sub-axial cervical spine. Additionally, the C2 pedicles may be identified on AP radiographic or fluoroscopic images whereas those of the sub-axial cervical spine are not well-seen. A hint of the the subchondral synchondrosis may be seen even after it is fused.

In certain clinical scenarios, particularly when access to the subarachnoid space cannot be achieved in the lumbar spine, access may be achieved at the C1-C2 level. In addition to meticulous training/technique, review of pre-procedure imaging to assess the size of this space (which varies) and to exclude an aberrant inferior dipping PICA artery in this location is essential.

The C0-C1 (atlantooccipital), C1-C2 (atlantoaxial), and subaxial cervical facet joints are true synovial joints. The C0-C1 and C1-C2 joints have characteristic orientations as shown above. The remaining facet joints have a shingles on a roof appearance on sagittal images, ladder-rung appearance on coronal image, and hamburger bun appearance on axial images.

The innervation of the cervical facet joints is important for diagnosis of facet joint pain and treatment with RF ablation. These receive dual innervation from the medial branches of the dorsal rami similar to most other spinal facet joints, but there are exceptions. Remembering which is as easy as 1-2-3.

Specifically, the C0-C1 joints are innervated by the C1 nerve, C1-C2 joints by articular branches from the C2 ventral ramus, the sinuvertebral nerve, and additional nerve fibers to the the ventral joint capsule, and the C2-C3 joints by the third occipital nerve.

The cervical intervertebral disc is less thoroughly studies than that of the lumbar spine. Although there are similarities, the cervical intervertebral disc cannot simply be regarded as an analog of the lumbar counterpart in terms of anatomy or clinical significance. Key differences include smaller size, lack of a substantial posterior anulus fibrosis between the uncinate processes (hence the annulus is crescent-shaped and nucleus pulposis is mostly contained by the PLL), smaller proportion of nucleus pulposis that becomes fibrotic with age to become a fibrocartilagenous core, and normal fissures that can extend centrally from the uncovertebral joint regions.

Reference

Mercer S, Phty (Hons) B, Bogduk N. The ligaments and anulus fibrosis of the human adult cervical intervertebral discs. Spine 1999;24(7):619-628

Note the lateral upticks underneath the uncovertebral joints.

The radiologist is frequently asked to assess the ligaments of the cervical spine in the setting of trauma.

The anterior longitudinal ligament (ALL) has multiple layers. The superficial layer spans many vertebral bodies and extends superiorly to the anterior arch of C1. The deeper layers span just one interspace and are closely associated with the anulus fibrosis.

The posterior longitudinal ligament (PLL) also has several layers and effectively replaces the function of the deficient posterior anulus.

The ligamentum flavum spans the lamina. The interspinous ligament opposes cervical flexion, may have indeterminate signal change with trauma, or may be torn with spinous process splaying. Superior to the C7 spinous process, the supraspinous ligament deviates dorsally to become the nuchal ligament which is unassociated with the spinous processes and extends to the occiput.

In addition, there are several key ligaments of the craniocervical junction depicted above.

Reference

Mercer S, Phty (Hons) B, Bogduk N. The ligaments and anulus fibrosis of the human adult cervical intervertebral discs. Spine 1999;24(7):619-628

The cervical spinal cord has a normal mild expansion around the C5-C6 level. At no point should a normal cervical spinal cord focally decrease in size relative to segments cranial and caudal to it. Central gray matter and peripheral white matter can be distinguished with some MRI pulse sequences. It is essential to understand the expected locations of major white matter tracts such as the corticospinal tracts, dorsal columns, or spinothalamic/anterolateral system as well as the anterior horn cells.

Characterization of pathology largely depends on the craniocaudal extent of abnormality and distribution within the spinal cord on axial images. (Other features are also important such as type, degree, and configuration of signal abnormality, presence and pattern of contrast enhancement, spinal cord expansion versus atrophy, and other supportive imaging and clinical findings).

An abnormality that extends over two vertebral bodies in craniocaudal distance may be considered longitudinally extensive.

Peripheral, short segment CE with spondylotic CE.

Short segment, peripheral-MS. NMO

Owl eyes and dorsal infarct

B12 deficiency.

Central for syrnix/pre-syrinx.

Hiraymama for epidural fat and spinal cord atrophy.