Match each lumbar MR image in Figure 117AD with the appropriate description Each image depicts a patient who presents with symptoms consistent with lumbar spinal stenosis

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1. Ligamentum flavum hypertrophy causing stenosis of the central spinal canal and lateral recess.

2. Hypertrophy of the superior articular process at L5-S1 associated with thickened ligamentum flavum and resulting in front-to-back narrowing of the L5-S1 intervertebral nerve root canal with compression of the L5 ganglion.

3. Synovial cyst arising from the L4-L5 facet joint, resulting in compression of the left side of the thecal sac and left L5 nerve root.

4. Degenerative spondylolisthesis associated with L4-L5 central spinal stenosis. Answers: (1), D; (2), C; (3), A; (4), B.

Figure 11-7. Lumbar Spinal Stenosis (A and C from Gundry CR, Heithoff KB, Pollei SR. Lumbar degenerative disk disease. Spine State Art Rev 1995;9:169. B from Barckhausen RR, Math KR. Lumbar spine diseases. In: Katz DS, Math KR, Groskin SA, editors: Radiology Secrets. Philadelphia: Hanley & Belfus; 1998. D from Figueroa RE, Stone JA. MR imaging of degenerative spine disease: MR myelography and imaging of the posterior spinal elements. In Castillo M, editor. Spinal Imaging: State of the Art. Philadelphia: Hanley & Belfus; 2001, with permission.

Figure 11-7. Lumbar Spinal Stenosis (A and C from Gundry CR, Heithoff KB, Pollei SR. Lumbar degenerative disk disease. Spine State Art Rev 1995;9:169. B from Barckhausen RR, Math KR. Lumbar spine diseases. In: Katz DS, Math KR, Groskin SA, editors: Radiology Secrets. Philadelphia: Hanley & Belfus; 1998. D from Figueroa RE, Stone JA. MR imaging of degenerative spine disease: MR myelography and imaging of the posterior spinal elements. In Castillo M, editor. Spinal Imaging: State of the Art. Philadelphia: Hanley & Belfus; 2001, with permission.

17. A 50-year-old diabetic man presents with a 2-month history of low back pain refractory to bedrest and analgesics. An MRI (Fig. 11-8) is obtained by the patient's primary physician, and the patient is referred for consultation. What is the diagnosis?

The imaging findings are classic for a disc space infection. Pyogenic infection typically begins at the vertebral endplates, then involves the disc, and finally spreads to involve the adjacent vertebral bodies. T1 -weighted images show decreased signal intensity in the disc and vertebral bodies. T2-weighted images show increased signal intensity in the disc and vertebral bodies. Additional findings may include inflammatory changes in the paravertebral soft tissues and abscess formation in either the epidural space or anterior paravertebral tissues.

Figure 11 -8. Magnetic resonance (MR) of Streptococcus pneumoniae discitis/osteomyelitis. A, Sagittal T1 -weighted conventional spine-echo (CSE) image reveals an extensive hypointensity involving the L4-L5 disc space (asterisk) and the adjacent vertebral bodies. An extradural soft tissue mass compresses the thecal sac (arrow). B, Sagittal T2-weighted CSE image shows mixed hyperintensity and isointensity in the involved L4-L5 intervertebral disc and adjacent vertebrae. C, Sagittal T1 -weighted CSE image following gadolinium administration reveals peripheral enhancement of the disc (straight arrows) and uniform enhancement of the epidural mass (curved arrows), representing discitis and epidural phlegmon. (From Reddy S, Leite CC, Jinkins JRZ. Imaging of infectious disease of the spine. Spine State Art Rev 1995;9:135, with permission.)

Figure 11 -8. Magnetic resonance (MR) of Streptococcus pneumoniae discitis/osteomyelitis. A, Sagittal T1 -weighted conventional spine-echo (CSE) image reveals an extensive hypointensity involving the L4-L5 disc space (asterisk) and the adjacent vertebral bodies. An extradural soft tissue mass compresses the thecal sac (arrow). B, Sagittal T2-weighted CSE image shows mixed hyperintensity and isointensity in the involved L4-L5 intervertebral disc and adjacent vertebrae. C, Sagittal T1 -weighted CSE image following gadolinium administration reveals peripheral enhancement of the disc (straight arrows) and uniform enhancement of the epidural mass (curved arrows), representing discitis and epidural phlegmon. (From Reddy S, Leite CC, Jinkins JRZ. Imaging of infectious disease of the spine. Spine State Art Rev 1995;9:135, with permission.)

18. A 70-year-old woman presents with back pain and a thoracic fracture. She has a history of breast cancer and a documented history of osteoporosis. How can MRI help determine whether the fracture is the result of osteoporosis or metastatic breast cancer?

Findings on MRI that support a diagnosis of metastatic tumor include abnormal marrow signal in other vertebrae, a convex posterior margin of the vertebral body (i.e. an expanded appearance), and compression of the entire vertebral body, including its posterior third. Additional features supporting a diagnosis of metastatic disease include involvement of the pedicle, presence of an extraosseous soft tissue mass, and diffuse marrow replacement throughout the vertebral body without focal fat preservation (Fig. 11-9).

Findings on MRI that support a diagnosis of a benign osteoporotic compression fracture include normal or mildly abnormal signal in the fractured vertebral body, a wedge-shaped vertebral body without compression of the posterior third, and a horizontally oriented low signal line paralleling the vertebral body endplate (Fig. 11-10).

MRI can be useful in determining the age of an osteoporotic vertebral fracture. The presence of marrow edema indicates that the fracture is relatively acute. The STIR pulse sequence is extremely sensitive to marrow edema. Gadolinium contrast will also show enhancement in acute fractures. The absence of marrow edema indicates a more chronic fracture.

The MRI findings in acute osteoporotic compression fractures may overlap the findings in cases of malignant collapse. Fracture edema and hemorrhage can surround a vertebral body and give the appearance of a soft tissue mass. Fracture-related edema in acute osteoporotic fractures may cause diffuse vertebral body enhancement similar to the findings in metastatic disease. However, after osteoporotic fractures heal, signal intensities in the collapsed and adjacent normal vertebral bodies are identical. In equivocal cases, a follow-up MR scan can be performed to reassess the bone marrow for resolution of signal abnormalities and reversion to normal fat signal. A CT-guided biopsy is indicated when questions about the cause of a spine fracture remain after imaging studies have been performed.

Figure 11-9. Bone metastasis. Arrows depict the posterior vertebral cortex, which has a smooth, diffuse bulge and convex contour. (From Palmer WE, Suri R. MR. Differentiation of benign versus malignant collapse. In: Castillo M, editor. Spinal Imaging: State of the Art. Philadelphia: Hanley & Belfus; 2001, with permission.)

Figure 11-9. Bone metastasis. Arrows depict the posterior vertebral cortex, which has a smooth, diffuse bulge and convex contour. (From Palmer WE, Suri R. MR. Differentiation of benign versus malignant collapse. In: Castillo M, editor. Spinal Imaging: State of the Art. Philadelphia: Hanley & Belfus; 2001, with permission.)

Figure 11-10. Benign osteoporotic compression fracture. Arrows depict a linear fracture plane. The line does not extend all the way to the posterior vertebral cortex and posterior cortical height is maintained. (From Palmer WE, Suri R. MR. Differentiation of benign versus malignant collapse. In: Castillo M, editor. Spinal Imaging: State of the Art. Philadelphia: Hanley & Belfus; 2001, with permission.)

Figure 11-10. Benign osteoporotic compression fracture. Arrows depict a linear fracture plane. The line does not extend all the way to the posterior vertebral cortex and posterior cortical height is maintained. (From Palmer WE, Suri R. MR. Differentiation of benign versus malignant collapse. In: Castillo M, editor. Spinal Imaging: State of the Art. Philadelphia: Hanley & Belfus; 2001, with permission.)

Key Points

1. MRI provides excellent visualization of pathologic processes involving the disc, thecal sac, epidural space, neural elements, paraspinal soft tissue, and bone marrow.

2. Gadolinium contrast-enhanced MRI of the spine is valuable for evaluating patients with infection, tumor, or history of prior decompressive surgery.

Website

Radiology web links: http://www.radswiki.net/main/index.php?title=Radiology websites MRI sequences: http://www.mr-tip.com/serv1.php?type=seq

BiBLiOGRAPHY

1. Castillo M, editor. Spinal Imaging: State of the Art. Philadelphia: Hanley & Belfus; 2001.

2. El-Khoury GY, Bennett L, Stanley M. Essential in Musculoskeletal Imaging. Philadelphia: Saunders; 2003.

3. Helms CA, Major NM, Kaplan PA, et al., editors. Helms: Musculoskeletal MRI. 2nd ed. Philadelphia: Saunders; 2008.

4. Resnick D, Kransdorf MJ, editors. Resnick: Bone and Joint Imaging. 3rd ed. Philadelphia: Saunders; 2005.

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