This chapter is entitled cross-sectional imaging anatomy of the spine. The imaging modalities most frequently used to evaluate the spine, are computed tomography or CT, magnetic resonance imaging or MRI, and CT myelography. CT uses x-rays to produce 360 degree views. It is the gold standard in evaluating osseous anatomy. It affords high resolution and an infinite number of planes. In addition, CT angiography is useful for evaluating vasculature of the spine. Although CT is rapid, it does result in radiation exposure. MRI uses magnetic field and radiofrequency pulses. It is the gold standard for soft tissue evaluation in the spine. Namely, neural ligamentous and disc. It does not result in radiation exposure, although it does result in longer exam times in CT. CT myelography is CT imaging after intrathecal injection of contrast material. It is useful for assessing the spine post surgery, for evaluating disc abnormalities, as well as tumors causing cord compression and those who cannot undergo MRI. Let's quickly review the anatomy of the cervical spine on CT. Here we have sagittal images from a cervical spine CT. We note the Bayesian and opecian, demarcating the frame among them. Here we have the dens or odontoid process of C2. The body of C2 and the spinous process of C2. In addition, we note the anterior arch of C1 and the posterior arch of C1. We note the intervertebral discs at the cervical spine levels, the cervical vertebra bodies, and the spinous processes from C3 to C7. As we scroll left and right, we note additional anatomy namely atlanto-occipital joint, the occipital condyle, and the lateral mass of C1, as well as the lateral mass of C2. As we continue to scroll we note the articular pillars, the superior articular facet, the inferior articular facet, and the intervening facet joints. Coronal images are very useful for evaluating the craniocervical junction. Here we note the occipital condyle, lateral masses of C1, dens or odontoid process of C2, lateral mass of C2, as well as body of C2. In addition, we note the articular pillars and facets in the sub axial cervical spine. In the axial plane we find the occipital condyles, as we scroll in fairly, we find the anterior arch of C1, the dens or odontoid process, the lateral masses of C1, the posterior arch of C1, the body of C2, the transverse foramen on either side, and the spinous process of C2. In the sub-axial cervical spine, we note the uncinate processes, a neural foramen, and as we scroll inferiorly, we find the transverse processes with the anterior and posterior tubercles, the vertebral foramen, or transverse foramen on either side, the pedicles, lamina, as well spinous processes. In addition, we note the facet joints with the inferior articular facet as well superior articular facet of the vertebral body below. Let's now turn our attention briefly to MRI of the cervical spine. The key to interpreting MRI is recognizing sequences or images with a particular appearance. When describing this appearance, we refer to the shade of grave tissues or fluid known as intensity. High signal intensity appears white, intermediate signal intensity appears gray, and low signal intensity appears black. In addition, we can refer to the appearance in relative terms by using the word hyperintense to denote something brighter than the thing we're comparing to, isointense to refer to the same brightness, or hyperintense to refer to something darker. All MRI studies of the cervical spine at the very least include a T1 weighted sequence seen in the top left which is thought of as the most anatomical images with fluid appearing low signal intensity, muscle appearing intermediate or gray, and fat appearing high signal intensity or a white, as well as a T2 weighted sequence seen in the top right in which fluid is high signal intensity, muscle is gray, and fat is white. In addition, we can suppress signal from fat to better detect fluid or edema, resulting in a so called STIR sequence seen on the bottom left. Additional sequences include susceptibility weighted imaging to detect blood products or calcium, diffusion-weighted imaging to assess how water molecules move around within a tissue, giving us insight into ischemia cellularity or edema, as well as contrast enhance images post gadolinium injection seen on the bottom right in order to examine pathological tissues and blood vessel integrity. To simplify, the two basic types of MRI sequences, T1 and T2 seen on the top, can be differentiated by the appearance of fat and water with T1 weighted sequences demonstrating break fat signal and T2 weighted sequences demonstrating bright fat and water signal. On spine images, the easiest way to differentiate these two is to look at the signal of the cerebral spinal fluid. Let's now correlate the anatomy on MRI to that which we saw on CT. On the left we have a T1 weighted sequence, and on the right a T2 weighted sequence of the cervical spine. Note once again that CSF is dark on the T1 weighted sequence and bright on the T2 weighted sequence. We have the cervical vertebra bodies once again and the intervening intervertebral disc spaces. We have the dens and body of C2, the anterior and posterior arch of C1, as well as the spinous processes seen posterior to the vertebrae. Please note that the signal from fat is both bright on T1 and T2 weighted sequences. In addition, in relatively young healthy patients, the bone marrow signal is slightly hyperintense to both disc and muscle on T1 weighted sequences. Additional anatomy seen on MRI includes the posterior fossa structures, the cerebellum hemispheres, the brain stem structures including the pons and medulla, as well as the pituitary gland, and optic chiasm. Moreover, we note the clivus and a portion of this sphenoid sinus. We see the nasopharyngeal structures, the adenoids, the lingual tonsils, the base of tongue, the epiglottis, and the trachea. An evaluation of MRI of the cervical spine is not complete without assessing spinal ligaments. Spinal ligaments appear hyperintense on both T1 and T2 weighted sequences. The major spinal ligaments include the anterior longitudinal ligament in the sagittal plane seen hugging the anterior aspect of the vertebral bodies. The posterior longitudinal ligament running along the posterior aspect of the vertebral bodies, as well as the ligamentum flavum forming a hyperintense line seen here. Additional ligaments include the tectorial membrane, the apical ligament, as well as the transverse atlanto-ligament posterior to the dense which would be better seen on the axial slices. Additional ligaments forming part of the posterior ligamentous complex includes the nuchal ligament seen here, appearing hyperintense, the supraspinous ligament connecting the tips of the spinous processes from C7 to the sacrum, as well as the interspinous ligaments appearing between the spinous processes. On the left we have axial T1 and on the right axial T2 weighted images of the cervical spine. Starting at the top we visualize the cerebellum hemispheres bilaterally, the pontomedullary junction, the clivus, and the vertebral arteries. As we scroll inferiorly, we see the medulla and the cervicomedullary junction. We note the lateral masses of C1, the anterior arch of C1, the dens or odontoid process, as well as this hyperintense line posterior to the dens representing the transfers atlanto-ligament. As we continue to scroll inferiorly, we note the body of C2. We note the nice uniform hyper intensity of the cervical spinal cord, and in addition, we note normal appearing bright CSF both anterior and posterior to the cord. Moreover, we note these nice hyperintense linear fossae traversing the CSF and exiting the ventral and dorsal aspect of the spinal cord consistent with the nerve rootlets entering the neural foramina. Additional anatomy includes the vertebral bodies, the facet joints, the lamina as well as the spinous processes. Extraosseous anatomy starting from the top includes the palatine tonsils, the adenoids, the parotid glands including the superficial and deep lobes, the masticator space muscles, as well as the dorsal paraspinal musculature.
