Let's briefly review the anatomy of the thoracic spine on CT. The thoracic spine consists of 12 vertebrae labeled T1 through T12. The thoracic spine is normally kyphotic with its apex centered at T7 and with this kyphosis increasing with age. The thoracolumbar junction located at T11 and T12, represents a transition zone from the more rigid thoracic spine to the more mobile lumbar spine. In addition, the thoracic vertebral bodies increase in size from T1 through T12. Here we find a magnified view of the mid to lower thoracic spine in the sagittal plane noting the vertebral bodies with their anterior cortex, posterior cortex, as well superior endplate and inferior endplate. As we scroll slightly left and right we note this small triangular shaped lucencies within the posterior half of the vertebral bodies, representing the basivertebral veins. In addition, note the intervening intervertebral discs at all the levels. Posteriorly, each vertebra is associated with a spinous process. As we scroll slightly out laterally, we find the lamina and further laterally we find the superior articular facet as well as the inferior articular facet with the facet joints. Here we note the bony pedicle as well as the neural foramina at each level. In the coronal plane, we note the spinous processes and as we scroll anteriorly, we find the lamina as well as the transverse processes and the ribs articulating with the transverse processes at the costotransverse joints. As we continue to scroll more anteriorly, we find the inferior articular facets, the superior articular facets, and the intervening facet joints. Scrolling further anteriorly, we find the pedicles as well as the vertebral bodies with their superior and inferior demi facets for the ribs at the costovertebral joints. Once again, please note this small lucencies within the posterior aspect of the vertebral bodies representing the basivertebral veins. In the axial plane, we see the vertebral body. Posteriorly, the spinal canal. We also not the pedicle, transverse process, as well as lamina and spinous process. Here we note the ribs as well as the costovertebral articulation and the costotransverse articulation. As we scroll further inferiorly, we come to the inferior articular facet as well as the superior articular facet of the vertebral body below and the intervening facet joint. Since a lot of this anatomy is redundant we will just quickly point out some features of thoracic spine MRI. Here on the left we have a T1-weighted sequence and on the right is sagittal T2-weighted sequence of the thoracic spine. We, once again, note the normal appearing thoracic vertebral bodies slightly hyperintense to muslin disc on T1, as well as the normal appearing disc spaces. Note that CSF is dark on the T1-weighted sequence and bright on the T2-weighted sequence. You'll also note this ill-defined appearing hypo intensity here posterior to the thoracic spinal cord on the T2-weighted sequence, which represent flow artifact. On both the T1 and T2-weighted sequences, we note normal uniform signal of the spinal cord. In addition, we note normal hypointensity of the spinal ligaments on T1 and T2-weighted sequences. Here the anterior longitudinal, the posterior longitudinal ligament, as well as the ligamentum flavum and supraspinous ligament. We also see the interspinous ligaments situated between the adjacent spinous processes. On T1-weighted sequences seen on the left, we also note this T1 hypointensity which is located outside the fecal sac in the extradural or epidural compartment consisted with normal epidural fat. Let's finally turn our attention briefly to describing the basic anatomy of the lumbar spine. Here we have representative CT images on the left and the sagittal plane and on the right in the coronal plane. We note the L1 through L5 vertebral bodies which are larger and they're transverse with than they are in their AP diameter. We have the anterior and posterior vertebral body cortices as well as the small lucencies when they need posterior half of the vertebral bodies representing the basivertebral veins. We have the superior and inferior vertebral endplates as well as the intervening intervertebral discs. Posteriorly, we note the spinous processes and centrally we note the spinal canal. In the coronal plane, we note once again the vertebral bodies and as we scroll posteriorly we find the transverse processes, the superior as well as inferior articular facets, the pars interarticularis, and the lamina. In the axial plane starting at the top of L2 we have the vertebral body, we have the superior articular facet of L2, the inferior articular facet of L1, and the facet joint. As we continue to scroll more inferiorly, we see the pedicle as well as transverse processes of L2, the central spinal canal, the lamina of L2, and as we continue to scroll more inferiorly we see the spinous process of L2 as well as inferior articular process of L2. We also note the intervertebral disc at L2-L3. Let's now briefly review the anatomy of the lumbar spine on MRI. Here we have T1 on the left and T2 weighted images on the right of the lumbar spine. We have normal lumbar lordosis, normal appearing lumbar vertebra bodies, and normal intervening intervertebral discs. It's important to note that the discs are comprised actually of an outer annulus fibrosus appearing hypointense normally on T2-weighted sequences and they essentially T2 hyperintense nucleus pulposus. As patients age, discs lose height and become desiccated and therefore discs become more hypointense on T2-weighted sequences. Additional anatomy includes the posterior spinous process as well as the spinal ligaments comprise of the anterior longitudinal ligament, posterior longitudinal ligament, ligamentum flavum, and supraspinous ligament. All appearing hypointense on both T1 and T2-weighted sequences. In addition, once again, note normal appearing extradural or epidural fat posterior to the fecal sac. As we scroll left and right more anatomy becomes evident. Here on the T1-weighted sequences we note the pedicles as well as the superior and inferior articular facets and the intervening facet joints. In addition, we see the neural foramen with the exiting nerve roots. It's important to note that unlike in the cervical spine where the spinal nerves exit above their corresponding vertebral body level, and the thoracic and lumbar spine the nerves actually exit below their corresponding vertebra body level. Given that C8 exits in between T1 and C7 and then there is no CA vertebral body. In terms of neuroanatomy, here we see the conus medullaris, the most distal bulbous portion of the spinal cord. Typically terminating anywhere from T12 through L2 and it's tapering and continuing as the filum terminale. On the sagittal slices we note normal fanning out of the cauda equina nerve roots as they enter the neural foramen which will be better demonstrated on the axial slices. On axial T2-weighted images of your lumbar spine, we visualize normal termination of the conus medullaris as well as the cauda equina or collective nerve roots distal to the conus medullaris occupying the lumbar cistern. As we scroll inferiorly, we note how these nerve roots fan out occupying the lumbar cistern and exiting through their respective neural foramina. Additional anatomy seen on lumbar spine MRI includes a portion of the liver, kidneys, pancreas, sometimes the gallbladder, as well as the abdominal aorta, IVC, spleen, and perhaps portions of the stomach. As we continue to scroll inferiorly, we note the psoas muscles on both sides of the vertebral column. The quadratus lumborum muscles and furthermore the erector spinae muscles dorsally and the iliacus muscles along the iliac wings. Here we have axial on the left and sagittal images on the right from a CT milligrams. As we scroll on the axial slices, we note the spinal cord and normal appearing conus medullaris as well as multiple nerve roots of the cauda equina which appear to fan normally and enter the neural foramina. Here we see more magnified sagittal images from the milligram demonstrating high attenuation contrast both ventral and dorsal to the spinal cord and therefore, outlining the normal anatomy. As you can imagine if there are a large discrimination or tumor compressing the spinal canal, this would appear as a contour deformity and would potentially even block contrast from flowing into the remaining portions of the spinal canal.
