10 Computed Tomography of Spinal Abnormalities(Table 10.3 – Table 10.4)

10.1055/b-0034-75795

10 Computed Tomography of Spinal Abnormalities(Table 10.3 – Table 10.4)

**Table 10.3 Multifocal lesions involving the spine**
Lesions	CT Findings	Comments
Neoplasms (malignant)
Metastatic tumor Fig. 10.29a–c	Single or multiple well-circumscribed or poorly defined infiltrative lesions involving the vertebral marrow, dura, and/or leptomeninges; low to intermediate attenuation; may show contrast enhancement, with or without medullary and cortical bone destruction (radiolucent), with or without bone sclerosis, with or without pathologic vertebral fracture, with or without epidural tumor extension causing compression of neural tissue or vessels. Leptomeningeal tumor often best seen on postcontrast images.	May have variable destructive or infiltrative changes involving single or multiple sites of involvement.
Myeloma/plasmacytoma Fig. 10.30a, b	Multiple (myeloma) or single (plasmacytoma), well- circumscribed or poorly defined, diffuse infiltrative radiolucent lesions involving the vertebra (e) and dura; involvement of vertebral body lesions typically radiolucent/bone lysis, rarely involves posterior elements until late stages; low to intermediate attenuation; may show contrast enhancement. Pathologic vertebral fracture, with or without epidural tumor extension causing compression of neural tissue or vessels.	Malignant monoclonal plasma cell tumors, may have variable destructive or infiltrative changes involving the axial and/or appendicular skeleton.
Lymphoma and leukemia Fig. 10.31a, b	Single or multiple, well-circumscribed or poorly defined infiltrative radiolucent lesions involving the marrow of the vertebrae, dura, and/or leptomeninges; low to intermediate attenuation, pathologic vertebral fracture, with or without epidural tumor extension causing compression of neural tissue or vessels. May show contrast enhancement, with or without bone destruction. Diffuse involvement of vertebra with Hodgkin lymphoma can produce bone sclerosis, as well as an “ivory” vertebra pattern, which has diffuse high attenuation. Leptomeningeal tumor often best seen on postcontrast images.	Tumors of malignant lymphocytes, may have variable destructive or infiltrative marrow/bony changes involving single or multiple vertebral sites. Lymphoma may extend from paraspinal lymphadenopathy into the verte-brae, adjacent soft tissues within or outside the spinal canal, initially involve only the epidural soft tissues or only the subarachnoid compartment. Can occur at any age (peak incidence third to fifth decades).
Neoplasms (benign)
Hemangioma	Circumscribed or diffuse vertebral lesion, usually radiolucent–deficiency of bone trabeculae, located in the vertebral body with or without extension into pedicle or isolated within pedicle; typically have low to intermediate attenuation with thickened vertical trabeculae; can show contrast enhancement; multiple in 30%. Location: thoracic (60%) > lumbar (30%) > cervical (10%).	Most common benign lesions involving vertebral column, women > men, composed of endothelial-lined capillary and cavernous spaces within marrow associated with thickened vertical trabeculae and decreased secondary trabeculae; seen in 11% of autopsies. Usually asymptomatic, rarely cause bone expansion and epidural extension resulting in neural compression (usually in thoracic region); increased potential for fracture with epidural hematoma.
Other tumorlike lesions
Tarlov cyst (perineural cyst)	Well-circumscribed cysts with CSF attenuation involving nerve root sleeves associated with chronic erosive changes involving adjacent bony structures. Sacral (with or without widening of sacral foramina) > lumbar nerve root sleeves. Usually range from 15 to 20 mm in diameter but can be larger.	Typically represent incidental asymptomatic anatomical variants associated with prior dural injury.
Bone island	Usually appear as a circumscribed, radiodense, ovoid or spheroid focus in medullary bone that may or may not contact the endosteal surface of cortical bone.	Nonneoplastic intramedullary zones of mature compact bone composed of lamellar bone which are considered to be developmental anomalies resulting from localized failure of bone resorption during skeletal maturation.
Melorheostosis Fig. 10.32	Attenuation of these lesions is based on the relative proportions of chondroid, mineralized osteoid, and soft tissue components. Mineralized zones typically have high attenuation along sites of thickened cortical bone; typically no contrast enhancement is seen in bone lesions. Nonmineralized portions can have low to intermediate attenuation and can show contrast enhancement. Osteopoikilosis typically appears as multiple circumscribed, radiodense, ovoid or spheroid foci in medullary bone that usually measure 3 to 5 mm. The long axis of the foci are often parallel to the adjacent bone trabeculae. Some foci may contact the endosteal surface of cortical bone.	Rare bone dysplasia with cortical thickening that has a “flowing candle wax” configuration. Associated soft tissue masses occur in ~25%. The soft tissue lesions often contain mixtures of chondroid material, mineralized osteoid, and fibrovascular tissue. Surgery is usually performed only for lesions causing symptoms. Osteopoikilosis (osteopathia condensans disseminate or spotted bone disease) is a sclerosing bone dysplasia in which numerous small round or oval radiodense foci are seen in medullary bone, giving the appearance of multiple bone islands. Can occur at any age, usually asymptomatic. In 25%, bone lesions may be associated with subcutaneous nodules, keloid formation, and scleroderma-like lesions (Buschke–Ollendorff syndrome). Osteopoikilosis may also occur as an overlap syndrome with other sclerosing bone dysplasias, such as melorheostosis and osteopathia striata.
Paget disease Fig. 10.33a, b	Expansile sclerotic/lytic process involving a single or multiple vertebrae with mixed intermediate to high attenuation. Irregular/indistinct borders between marrow cortical bone; can also result in diffuse sclerosis, “ivory” vertebral pattern.	Chronic disease with disordered bone resorption and woven bone formation. Usually seen in older adults, polyostotic in 66%; can result in narrowing of neuroforamina and spinal canal.
Trauma
Fracture Fig. 10.34a, b Fig. 10.35	Traumatic and osteopenic vertebral fracture: Acute/subacute fractures have sharply angulated cortical margins, no destructive changes at cortical margins of fractured end plates. With or without convex outward angulated configuration of compressed vertebral bodies, with or without spinal cord and/or spinal canal compression related to fracture deformity, with or without retropulsed bone fragments into spinal canal, with or without subluxation, with or without kyphosis, with or without epidural hematoma. Malignancy-related vertebral fracture: Fractures related to radiolucent and/or sclerotic lesions, with or without destructive changes at cortical margins of vertebrae, with or without convex outward-bowed configuration of compressed vertebral bodies, with or without paravertebral mass lesions, with or without spheroid or poorly defined lesions in other noncompressed vertebral bodies.	Vertebral fractures can result from trauma, primary bone tumors/lesions, metastatic disease, bone infarcts (steroids, chemotherapy, and radiation treatment), osteoporosis, osteomalacia, metabolic (calcium/phosphate) disorders, vitamin deficiencies, Paget disease, and genetic disorders (osteogenesis imperfecta, etc.).
Inflammation/infection
Pyogenic vertebral osteomyelitis/diskitis Fig. 10.36a, b	Poorly defined radiolucent zones involving the end plates and subchondral bone of two or more adjacent vertebral bodies, with or without fluid collections in the adjacent paraspinal soft tissues; may show contrast enhancement in marrow and paravertebral soft tissues; variable enhancement of disk (patchy zones within disk) and/or thin or thick peripheral enhancement; with or without epidural abscess/paravertebral abscess; with or without vertebral compression deformity; with or without spinal cord or spinal canal compression.	Vertebral osteomyelitis represents 3% of osseous infections, results from hematogenous source (most common) from distant infection or intravenous (IV) drug abuse; complication of surgery, trauma, diabetes; spread from contiguous soft tissue infection. Initially involves end arterioles in marrow adjacent to end plates with eventual destruction and spread to the adjacent vertebrae through the disk. Seen in children and adults older than 50 y. Gram-positive organisms (Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus, etc.) account for 70% of pyogenic osteomyelitis, and gram-negative organisms (Pseudomonas aeruginosa, Escherichia coli, Proteus, etc.) represent 30%. Fungal osteomyelitis can appear similar to pyogenic infection of spine.
Vertebral osteomyelitis tuberculosis Fig. 10.37a–c	Poorly defined radiolucent zones involving the end plates and subchondral bone of two or more adjacent vertebral bodies, with or without fluid collections in the adjacent paraspinal soft tissues; may show contrast enhancement in marrow and paravertebral soft tissues; variable enhancement of disk (patchy zones within disk) and/or thin or thick peripheral enhancement; with or without epidural abscess/paravertebral abscess; with or without vertebral compression deformity; with or without spinal cord or spinal canal compression. Can show limited disk involvement early in disease process.	Initially involves marrow in the anterior portion of the vertebral body with spread to the adjacent vertebrae along the anterior longitudinal ligament, often sparing the disk until later in disease process; usually associated with paravertebral abscesses that may be more prominent than the vertebral abnormalities.
Rheumatoid arthritis	Erosions of vertebral end plates, spinous processes, and uncovertebral and apophyseal joints. Irregular enlarged enhancing synovium (pannus: low to intermediate attenuation) at atlantodens articulation results in erosions of dens and transverse ligament, with or without destruction of transverse ligament with C1 on C2 subluxation and neural compromise; with or without basilar impression.	Most common type of inflammatory arthropathy that results in synovitis, causing destructive/erosive changes of cartilage, ligaments, and bone. Cervical spine involvement seen in two thirds of patients, juvenile and adult types.
Ankylosing spondylitis Fig. 10.38a, b	Inflammation occurs at entheses (sites of attachment of ligaments, tendons, and joint capsules to bone). Squaring of vertebral bodies with mineralized syndesmophytes across many disks, osteopenia, erosions at sacroiliac joints with eventual fusion across these joints and facets. The spine in these cases is referred to as “bamboo spine.”	Chronic progressive autoimmune inflammatory disease involving the spine and sacroiliac joints. Associated with human leukocyte antigens (HLA) B27 in 90%, onset in patients 20 to 30 y old, M:F 3:1. Fractures can occur in the horizontal plane through the osteopenic and fused “bamboo spine” at the level of the disks and/or vertebral bodies, as well as involving the posterior elements.
Eosinophilic granuloma	Single or multiple, circumscribed radiolucent lesions in the vertebral body marrow associated with focal bony destruction/erosion with extension into the adjacent soft tissues. Lesions usually have low to intermediate attenuation and involve the vertebral body and not the posterior elements; can show contrast enhancement, with or without enhancement of the adjacent dura. Progression of lesion can lead to vertebra plana (collapsed flattened vertebral body) with minimal or no kyphosis and relatively normal-sized adjacent disks.	Single lesion: Commonly seen in male patients younger than 20 y; proliferation of histiocytes in medullary cavity with localized destruction of bone with extension into adjacent soft tissues. Multiple lesions: Associated with syndromes such as Letterer–Siwe disease (lymphadenopathy, hepatospleno megaly), children younger than 2 y; Hand–Schüller–Christian disease (lymphadenopathy, exophthalmos, diabetes insipidus), children 5 to 10 y old.
Sarcoidosis	Sarcoid lesions can be multiple with variable sizes or solitary within marrow. Lesions can have circumscribed and/or indistinct margins within marrow and usually are radiolucent with low to intermediate attenuation; rarely are sclerotic; can show contrast enhancement.	Chronic systemic granulomatous disease of unknown etiology in which noncaseating granulomas occur in various tissues and organs, including bone.
Mastocytosis Fig. 10.39a–c	Radiographs and CT can show indistinctly marginated sclerotic lesions, radiolucent zones, or mixed sclerotic and radiolucent lesions in medullary bone.	Heterogeneous uncommon disorders with pathologic accumulation of mast cells in various tissues (age ranges from first to seventh decades, mean in fourth decade) and can be classified into four clinical categories. Category 1 is the most common and includes 1A, which involves the skin (cutaneous mastocytosis or urticaria pigmentosa), and 1B or systemic mastocytosis, with mast cells occurring in various tissues (bone marrow, spleen, gastrointestinal [GI] tract, and lymph nodes). Category 1 usually has a favorable prognosis. Category 2 includes mastocytosis associated with a myeloproliferative or myelodysplastic disorder. Prognosis depends on the associated degree of myelodysplasia. Category 3 (lymph-adenopathic mastocytosis with eosinophilia or aggressive mastocytosis) is associated with a poor prognosis related to large mast cell burdens. Category 4 results from mast cell leukemia and has a very poor prognosis.
Hematopoietic
Hematopoietic disorders	Red marrow hyperplasia can be seen as diffuse expansion of the diploic space of the skull with or without thinning of cortical bone.	Red marrow reconversion from erythroid hyperplasia can result from anemia secondary to sickle cell disease, thalassemia major, hereditary spherocytosis. Similar findings of red marrow expansion can be seen with polycythemia rubra. Medications (such as exogenous erythropoietin and granulocyte macrophage colony-stimulating factor in patients with anemia and neutropenia, respectively) can also cause red marrow reconversion in adults and children.
Extramedullary hematopoiesis	Lesions can have low or intermediate attenuation depending on the proportions and distribution of fat and red marrow.	Represents proliferation of erythroid precursors outside medullary bone secondary to physiologic compensation for abnormal medullary hematopoiesis from congenital disorders such as hemoglobinopathies (sickle cell, thalassemia, etc.), as well as acquired disorders, such as myelofibrosis, leukemia, lymphoma, myeloma, or metastatic carcinoma.
Bone infarcts	Focal ringlike lesion or poorly defined zone with increased attenuation in medullary bone; usually no contrast enhancement, with or without associated fracture.	Bone infarcts can occur after radiation treatment, surgery, corticosterioid medications, chemotherapy, or trauma.
Congenital
Dural ectasia	Scalloping of the dorsal aspects of vertebral bodies, dilation of optic nerve sheaths, dilation of intervertebral and sacral foraminal nerve sheaths, lateral meningoceles.	Dural dysplasia associated with NF1. Dural ectasia can also result from Marfan syndrome.

**Fig. 10.29a–c Metastatic disease.** Sagittal image (a) shows osteosclerotic and osteolytic metastatic lesions involving multiple vertebrae, as well as a compression fracture of the T1 vertebral body. Sagittal (b) and axial (c) images in another patient show osteolytic tumors.

**Fig. 10.30a, b Multiple myeloma.** Sagittal images (**a,b**) show multiple osteolytic lesions in multiple vertebrae.

**Fig. 10.31a, b Hodgkin lymphoma.** Sagittal (a) and axial (b) images show multiple osteosclerotic lesions.

**Fig. 10.32 Melorheostosis, 53-year-old man.** Sagittal image shows heavily ossified zones and thickened cortical bone involving multiple cervical vertebrae.

**Fig. 10.33a, b Paget disease.** Sagittal images show expansile osteosclerotic changes involving a thoracic vertebra with mixed intermediate and high attenuation. Irregular/indistinct borders between marrow and cortical bone are seen. Similar but less pronounced findings are seen in another vertebra two levels above (arrows).

**Fig. 10.34a, b Fracture, traumatic.** Sagittal images show severe unstable compression fractures of adjacent thoracic vertebrae with displaced fragments within the spinal canal.

**Fig. 10.35 Fracture, osteoporotic.** Sagittal image shows diffuse osteopenia and compression fracture deformities involving the L3 and L2 vertebral bodies.

**Fig. 10.36a, b Osteomyelitis.** Sagittal (a) and axial (b) postmyelographic CT images show destructive changes involving the end plates of two adjacent vertebral bodies from pyogenic osteomyelitis/diskitis.

**Fig. 10.37a–c Osteomyelitis, tuberculosis.** Sagittal (a) and coronal (b) images show destructive changes involving the end plates of two adjacent vertebral bodies, as well as paraspinal collections representing old abscesses (arrows). Abnormal contrast enhancement is seen at the site of infection on a sagittal fat-suppressed, T1-weighted image (c).

**Fig. 10.38a, b Ankylosing spondylitis.** Sagittal images show squaring of vertebral bodies with mineralized syndesmophytes across the disks, osteopenia, and fusion across the facet joints (“bamboo spine”). Also seen is a horizontally oriented fracture through the upper thoracic spine.

**Fig. 10.39a–c Mastocytosis.** Axial images show multiple sclerotic foci within multiple vertebrae.

**Table 10.4 Spine: Extradural lesions**
Lesions	CT Findings	Comments
Neoplasms
Metastatic tumor Fig. 10.40	Single or multiple, well-circumscribed or poorly defined lesions involving the vertebral marrow, dura, and/or leptomeninges; low to intermediate attenuation; usually with contrast enhancement, with or without bone destruction, with or without pathologic vertebral fracture, with or without compression of neural tissue or vessels. Leptomeningeal tumor often best seen on postcontrast images.	Metastatic tumor may have variable destructive or infiltrative changes involving single or multiple sites of involvement.
Lymphoma Fig. 10.41a–c	Single or multiple well-circumscribed or poorly defined infiltrative lesions involving the vertebrae, epidural soft tissues, dura, and/or leptomeninges; low to intermediate attenuation; usually with contrast enhancement, with or without bone destruction. Diffuse involvement of vertebra with Hodgkin lymphoma can produce an “ivory” vertebra. Leptomeningeal tumor often best seen on postcontrast images.	Lymphoma may have variable destructive or infiltrative marrow/bony changes involving single or multiple vertebral sites. Lymphoma may extend from bone into adjacent soft tissues within or outside the spinal canal or initially involve only the epidural soft tissues or only the subarachnoid compartment. Can occur at any age (peak incidence third to fifth decades).
Myeloma/plasmacytoma Fig. 10.42a, b	Multiple (myeloma) or single (plasmacytoma), well- circumscribed or poorly defined diffuse infiltrative lesions involving the vertebra (e), and dura; involvement of vertebral body typical; rarely involves posterior elements until late stages, low to intermediate attenuation, usually with contrast enhancement, with bone destruction.	Myeloma may have variable destructive or infiltrative changes involving the axial and/or appendicular skeleton.
Osteosarcoma Fig. 10.43a, b	Destructive malignant lesions, usually with matrix miner-alization/ossification within lesion or within extraosseous tumor extension; can show contrast enhancement (usually heterogeneous). Cortical bone destruction and epidural extension of tumor can compress the spinal canal and spinal cord.	Malignant bone lesions rarely occur as primary tumor involving the vertebral column, locally invasive, high metastatic potential. Occurs in children as primary tumors and adults (associated with Paget disease, irradiated bone, chronic osteomyelitis, osteoblastoma, giant cell tumor, and fibrous dysplasia).
Chordoma Fig. 10.44a–d	Well-circumscribed, lobulated radiolucent lesions, low to intermediate attenuation; usually shows contrast enhancement (usually heterogeneous); locally invasive associated with bone erosion/destruction; usually involves the dorsal portion of the vertebral body with extension toward the spinal canal. Also occurs in sacrum.	Rare, slow-growing, destructive notochordal tumors (~3% of bone tumors); usually occur in adults 30 to 70 y; M > F (2:1); sacrum (50%) > skull base (35%) > vertebrae (15%).
Chondrosarcoma Fig. 10.45a–c	Lobulated radiolucent lesions, low to intermediate attenuation, with or without matrix mineralization; may show contrast enhancement (usually heterogeneous); locally invasive associated with bone erosion/destruction, encasement of vessels and nerves; can involve any portion of the vertebra.	Rare, slow-growing, malignant cartilaginous tumors (~16% of bone tumors), usually occur in adults (peak in fifth to sixth decades), M > F; sporadic (75%), malignant degeneration/transformation of other cartilaginous lesion enchondroma, osteochondroma, etc. (25%).
Aneurysmal bone cyst Fig. 10.46a, b	Circumscribed vertebral lesion usually involving the posterior elements with or without involvement of the vertebral body; with variable low, intermediate, high, and/or mixed attenuation, with or without surrounding thin shell of bone, with or without lobulations, with or without one or multiple fluid–fluid levels, with or without pathologic fracture.	Expansile blood/debris filled lesions that may be primary or occur secondary to other bone lesions, such as giant cell tumor, fibrous dysplasia, and chondroblastoma. Most occur in patients younger than 30 y. Locations: lumbar > cervical > thoracic. Clinical findings can include neurologic deficits and pain.
Hemangioma Fig. 10.47a–d	Circumscribed or diffuse vertebral lesion, usually radiolucent–destruction of bone trabeculae, located in the vertebral body with or without extension into pedicle or isolated within pedicle; typically low to intermediate attenuation with thickened vertical trabeculae; can show contrast enhancement; multiple in 30%. Location: thoracic (60%) > lumbar (30%) > cervical (10%). Occasionally, lesions extend from bone into the epidural soft tissues.	Most common benign lesions involving vertebral column, F > M; composed of endothelial-lined capillary and cavernous spaces within marrow associated with thickened vertical trabeculae and decreased secondary trabeculae; seen in 11% of autopsies. Usually asymptomatic; rarely cause bone expansion and epidural extension resulting in neural compression (usually in thoracic region); increased potential for fracture with epidural hematoma.
Osteochondroma Fig. 10.48	Circumscribed sessile or protuberant osseous lesion typically arising from posterior elements of vertebrae, central zone contiguous with medullary space of bone, with or without cartilaginous cap. Increased malignant potential when cartilaginous cap is > 2 cm thick.	Benign cartilaginous tumors arising from defect at periphery of growth plate during bone formation with resultant bone outgrowth covered by a cartilaginous cap. Usually benign lesions unless associated with pain and increasing size of cartilaginous cap. Can occur as multiple lesions (hereditary exostoses) with increased malignant potential.
Paget disease Fig. 10.49a, b	Expansile sclerotic/lytic process involving a single or multiple vertebrae with mixed intermediate to high attenuation. Irregular/indistinct borders between marrow cortical bone; can also result in diffuse sclerosis, “ivory” vertebral pattern.	Chronic disease with disordered bone resorption and woven bone formation. Usually seen in older adults, polyostotic in 66%; can result in narrowing of neuroforamina and spinal canal.
Melorheostosis Fig. 10.50a, b	Attenuation of these lesions is based on the relative proportions of chondroid, mineralized osteoid, and soft tissue components. Mineralized zones typically have high attenuation along sites of thickened cortical bone; typically no contrast enhancement is seen in bone lesions. Nonmineralized portions can have low to intermediate attenuation and can show contrast enhancement.	Rare bone dysplasia with cortical thickening that has a “flowing candle wax” configuration. Associated soft tissue masses occur in ~25%. The soft tissue lesions often contain mixtures of chondroid material, mineralized osteoid, and fibrovascular tissue. Surgery is usually performed only for lesions causing symptoms.
Neoplasms and other masses
Schwannoma (neurinoma)	Circumscribed or lobulated extramedullary lesions, intermediate attenuation, with contrast enhancement. Contrast enhancement can be heterogeneous in large lesions due to cystic degeneration and/or hemorrhage.	Encapsulated neoplasms arising asymmetrically from nerve sheath; most common type of intradural extramedullary neoplasm; usual presentation in adults with pain and radiculopathy, paresthesias, and lower extremity weakness. Multiple schwannomas seen with NF2.
Neurofibroma	Lobulated extramedullary lesions with or without irregular margins, with or without extradural extension of lesion with dumbbell shape, intermediate attenuation, with contrast enhancement. Contrast enhancement can be heterogeneous in large lesions; with or without erosion of foramina, with or without scalloping of dorsal margin of vertebral body (chronic erosion or dural ectasia/NF1).	Unencapsulated neoplasms involving nerve and nerve sheath; common type of intradural extramedullary neoplasm often with extra-dural extension; usual presentation in adults with pain and radiculopathy, paresthesias, and lower extremity weakness. Multiple neurofibromas seen with NF1.
Hemangiopericytoma	Extra- or intradural extramedullary lesions; can involve vertebral marrow, often well circumscribed, intermediate attenuation, with contrast enhancement (may resemble meningiomas), with or without associated erosive bone changes.	Rare neoplasms in young adults (M > F) sometimes referred to as angioblastic meningioma or meningeal hemangiopericytoma; arise from vascular cells/pericytes; frequency of metastases > meningiomas.
Arachnoid cyst	Well-circumscribed intradural extramedullary lesions with low attenuation similar to CSF, no contrast enhancement; with or without associated erosive bone changes.	Nonneoplastic congenital, developmental, or acquired extra-axial lesions filled with CSF; usually mild mass effect on adjacent spinal cord or nerve roots.
Teratoma	Circumscribed lesions with variable low, intermediate, and/or high attenuation; with or without contrast enhancement. May contain calcifications and cysts, as well as fatty components that can cause chemical meningitis if ruptured.	Second most common type of germ cell tumors; occurs in children, M > F; benign or malignant types; composed of derivatives of ectoderm, mesoderm, and/or endoderm.
Disk herniation
Preoperative Fig. 10.51 Fig. 10.52a, b Fig. 10.53a, b Fig. 10.54a, b	Disk herniation/protrusion: Disk herniation in which the head of the protruding disk is equal in size to the neck on sagittal reconstructed images; disk herniation usually similar in attenuation to disk of origin. Can be midline in position, off-midline in lateral recess, posterolateral within intervertebral foramen, lateral or anterior; with or without compression or displacement of thecal sac and/or nerve roots in lateral recess and/or foramen.	Type of disk herniation (focal > broad-based) that results from inner annular disruption or subtotal annular disruption with extension of nucleus pulposus toward annular weakening/disruption with expansive deformation.
	Disk herniation/extrusion: Disk herniation in which the head of the disk herniation is larger than the neck on sagittal reconstructed images; attenuation of disk herniation usually similar to disk of origin. Can be midline, off-midline in lateral recess, posterolateral within intervertebral foramen, lateral, or anterior. Can extend superiorly, inferiorly, or both directions; with or without associated epidural hematoma; with or without compression or displacement of thecal sac and/or nerve roots in lateral recess and/or foramen. Can be calcified or contain gas if originating from a disk with vacuum phenomenon. Disk herniation/extruded disk fragment: Disk herniation that is not in contiguity with disk of origin, attenuation of disk herniation usually similar to disk of origin. Can be midline, off-midline in lateral recess, posterolateral within intervertebral foramen, lateral, or anterior. Can extend superiorly, inferiorly, or both directions. Rarely extend into dorsal portion of spinal canal or into thecal sac; with or without associated epidural hematoma; with or without compression or displacement of thecal sac and/or nerve roots in lateral recess and/or foramen.	Type of disk herniation (focal > broad-based) with extension of nucleus pulposus through zone of annular disruption with expansive deformation. Herniated fragment of nucleus pulposus without connection to disk of origin.
Postoperative edema, scar/granulation tissue	Postdiskectomy changes: Soft tissue material located in anterior epidural space with intermediate attenuation; with or without mass effect on thecal sac resulting from edema and tissue injury from surgery; with or without contrast enhancement; changes progressively involute after 2 months.	Changes from diskectomy evolve from localized edema with or without hematoma with mass effect on the thecal sac during the immediate postoperative period to granulation tissue and scar (peridural fibrosis), which may show contrast enhancement usually without associated mass effect, with or without retraction of adjacent structures.
Degenerative changes
Posterior disk bulge/osteophyte complex Fig. 10.55a–c	Diffuse broad-based bulge of disk usually with accompanying osteophytes from the adjacent vertebral bodies. Disks usually have decreased heights, low to intermediate attenuation related to disk degeneration and desiccation of the nucleus pulposus; with or without vacuum disk phenomenon.	With aging, altered disk metabolism, trauma, or biomechanical overload; the proteoglycan content in a disk can decrease resulting in disk desiccation, loss of turgor pressure in the disk, decreased disk height, bulging of the anulus fibrosus, with or without spinal canal stenosis, with or without narrowing of the intervertebral foramina, with or without thickening of spinal ligaments.
Degenerative facet hypertrophy Fig. 10.56a, b	Hypertrophic degenerative facets indent the dorsal lateral margins of the thecal sac and can result in spinal canal stenosis.	Degenerative arthritic changes involving the facet joints often lead to facet hypertrophy, which can result in spinal canal stenosis, usually in association with posterior disk bulge/osteophyte complexes.
Ossification of the posterior longitudinal ligament (PLL) Fig. 10.57a, b	Occurs as midline ossification at the dorsal aspects of the disks and vertebral bodies over several levels. A thin radiolucent line may be seen between the PLL and dorsal vertebral body margin secondary to connective tissue between the nonossified inner layer and ossified outer layers of the PLL.	The PLL extends from the C2 level to the sacrum and is attached to the anulus fibrosus of the disks and dorsal margins of the vertebral bodies. Ossification of the outer fibers of the PLL consists of lamellar bone and calcified cartilage, involves the cervical spine in 70%, thoracic in 15%, and lumbar region in 15%. Can result in spinal canal stenosis.
Synovial cyst Fig. 10.58a, b	Circumscribed structure located adjacent to the medial aspect of a degenerated facet joint, thin rim of intermediate attenuation surrounding a central zone that can have low or intermediate attenuation. Typically no contrast enhancement centrally.	Represents protrusion of synovium with fluid (ganglion cyst) from degenerated facet joint into spinal canal; variable MRI signal related to contents that may include mucinous or serous fluid, blood, hemosiderin, or air.
Fracture fragments Fig. 10.59a, b	Acute/subacute fractures have sharply angulated cortical margins, no destructive changes at cortical margins of fractured end plates; with or without convex outward angulated configuration of compressed vertebral bodies, with or without spinal cord and/or spinal canal compression related to fracture deformity, with or without retropulsed bone fragments into spinal canal, with or without subluxation, with or without kyphosis, with or without epidural hematoma.	Vertebral fractures can result from trauma, primary bone tumors/lesions, metastatic disease, bone infarcts (steroids, chemotherapy, and radiation treatment), osteoporosis, osteomalacia, metabolic (calcium/phosphate) disorders, vitamin deficiencies, Paget disease, and genetic disorders (osteogenesis imperfecta, etc.).
Epidural hematoma	Epidural collection with variable low, intermediate, and/or slightly high attenuation, with or without spinal cord compression.	Attenuation of epidural hematomas can vary secondary to stage of blood clotting and hematocrit. Older epidural hematomas can have mixed attenuation related to the various states of hemoglobin and breakdown products. Can be spontaneous or result from trauma or complication from coagulopathy, lumbar puncture, myelography, or surgery.
Spondylolysis Fig. 10.60a, b	Spondylolisthesis associated with cortical discontinuity of one or both pars interarticularis regions.	Fractures of the pars interarticularis regions from traumatic or stress injuries can lead to spondylolisthesis with narrowing of the spinal canal and/or neural foramina.
Epidural abscess Fig. 10.61a, b	Epidural collection with low signal attenuation surrounded by a peripheral rim (thin or thick) of contrast enhancement, with or without associated vertebral osteomyelitis/diskitis, with or without air collections, often extend over two to four vertebral segments; can result in compression of spinal cord and spinal canal contents.	Epidural abscess can evolve from an inflammatory phlegmonous epidural mass, extension from paravertebral inflammatory process or vertebral osteomyelitis/diskitis. May be associated with complications from surgery, epidural anesthesia, diabetes, distant source of infection, immunocompromised status. Organisms commonly involved include S. aureus, gram-negative bacteria, tuberculosis, coccidioidomycosis, candidiasis, aspergillosis, and blastomycosis. Clinical findings include back and radicular pain, with or without paresthesias and paralysis of lower extremities.
Epidural lipomatosis Fig. 10.62	Increased extradural fat is seen within the spinal canal with resultant narrowing of the thecal sac.	Epidural lipomatosis is a condition in which there is prominent deposition of unencapsulated mature adipose tissue in the epidural space. May be related to obesity, chronic use of steroid medication, or endogenous hyper-cortisolemia. Thoracic 60%, lumbar 40%.
Inflammation/infection
Rheumatoid arthritis Fig. 10.63a, b	Erosions of vertebral end plates, spinous processes, and uncovertebral and apophyseal joints. Irregular enlarged synovium (pannus: intermediate attenuation) at atlantodens articulation results in erosions of dens and transverse ligament, with or without destruction of transverse ligament with C1 on C2 subluxation and neural compromise, with or without basilar impression.	Most common type of inflammatory arthropathy that results in synovitis, causing destructive/erosive changes of cartilage, ligaments, and bone. Cervical spine involvement seen in two thirds of patients, juvenile and adult types.
Eosinophilic granuloma Fig. 10.64a, b	Single or multiple, circumscribed soft tissue lesions in the vertebral body marrow associated with focal bony destruction/erosion with extension into the adjacent soft tissues. Lesions usually involve the vertebral body and not the posterior elements, with low to intermediate attenuation, with or without contrast enhancement, with or without enhancement of the adjacent dura. Progression of lesion can lead to vertebra plana (a collapsed flattened vertebral body), with minimal or no kyphosis and relatively normalsized adjacent disks.	Single lesion: Commonly seen in male patients younger than 20 y; proliferation of histiocytes in medullary cavity with localized destruction of bone with extension into adjacent soft tissues. Multiple lesions: Associated with syndromes such as Letterer–Siwe disease (lymphadenopathy, hepatosplenomegaly), children younger than 2 y; Hand–Schüller–Christian disease (lymphadenopathy, exophthalmos, diabetes insipidus), children 5 to 10 y old.
Gout	Radiographic features may include erosions at the diskovertebral junctions or facet joints, osteophytes, spinal deformities with subluxations and pathologic fractures. Soft tissue swelling with or without calcifications can be seen with tophi that occur in the late phases of gout. Tophi often have 160 HU, which may be used for narrowing the differential diagnosis with respect to other joint diseases.	Inflammatory disease involving synovium resulting from deposition of monosodium urate crystals. Occurs when the serum urate level exceeds its solubility in various tissues and body fluid (> serum urate level of 7 mg/dL in men and 6 mg/dL in women). Can be a primary disorder of hyperuricemia resulting from inherited metabolic defects in purine metabolism or inherited abnormalities involving renal tubular secretion of urate. Primary gout accounts for up to 90% of cases in men. Secondary gout results from acquired metabolic alterations caused by medications (thiazide diuretics, alcohol, salicylates, and cyclosporine) that diminish renal excretion of uric acid salts.
Calcium pyrophosphate deposition disease (CPDD) Fig. 10.65a, b	Radiographs and CT show chondrocalcinosis, which can be seen at the C1–odontoid articulation. At C1–C2, hypertrophy of synovium may occur, which can have low to intermediate attenuation containing calcifications seen with CT.	CPDD is a common disorder usually seen in older adults in which there is deposition of calcium pyrophosphate crystals resulting in calcifications of hyaline and fibrocartilage; associated with cartilage degeneration, subchondral cysts, and osteophyte formation. Symptomatic CPDD is referred to as pseudogout because of overlapping clinical features with gout. Usually occurs in the knee, hip, shoulder, elbow, and wrist, rarely at the odontoid–C1 articulation.