1	Back Pain Imaging Adam Guttentag M.D.
2	Wasted time? Radiology departments do lots of imaging for low back pain. X-rays, CT, MRI etc. How much makes a difference? Studies show advanced imaging in acute back pain and sciatica doesn’t change outcomes, but improves diagnostic confidence.
3	Causes of back pain and sciatica Paraspinal muscles and ligaments Synovial joints: Facet and sacroiliac joints Disc disease Tear of annulus fibrosis Specific nerve root impingements Spondylosis Spinal stenosis Foraminal stenosis Bone disease Tumor Fracture Infection Epidural abscess discitis
4	Acute Back Pain 2^nd most common complaint to primary care physician >75% of adults will suffer it at some time. 90% will resolve without intervention (or imaging), most without a specific dx. Among patients with sciatica, only <10% will need surgery. Whom to image?
5	Back pain imaging — false positives Most adults over 40 will have degenerative changes on x-rays MRI shows disc pathology in the majority of adults Many asymptomatic people have disc bulges and protrusions. So, imaging is likely to result in an abnormal report. But correlation between radiographic findings and clinical symptoms is poor. When to image?
6	When to image in patients with acute back pain? Most authorities suggest conservative treatment for 4-6 weeks unless there are “red flags”: Look for historical and physical findings that raise clinical question of infection, tumor, or serious neurological impairment Even positive findings of degenerative disease like disc extrusions and spinal stenosis are not urgent and will be treated conservatively at first.
7	“Red flags” for early imaging Severe progressive neurological deficit Fracture? Major trauma or minor trauma in osteoporotic pt. Tumor? History of cancer, weight loss Pain worse at night or when supine Infection? Recent bacterial infection, immune supression, fever, IVDA
8	Imaging options Radiography CT Better for fine bone detail, arthritis As good as MRI for acute disc disease Myelography as adjunct MRI Very good for disc, paraspinal pathology, stenosis Infection Marrow disorders Contrast for infection, post-op, tumor Bone scan Not for primary imaging in most cases Discography
9	Radiography AP and lateral films Oblique films Flexion / extension films
10	Radiography Diagnoses that can be made on AP and lateral: Spondylolisthesis Compression fracture SI joint disease Disc degeneration Facet arthritis Tumor Infection in disc space
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12	Radiography Diagnosis best made on oblique films: Spondylolysis Facet arthritis Foraminal stenosis (cervical spine)
13	Radiography Diagnosis made with flexion / extension films: instability
14	Spondylolysis Stress fracture through pars interarticularis If bilateral, can cause spondylolisthesis
15	Cross Sectional Imaging: CT and MRI Why? Confirm extent of degenerative disease and spinal stenosis. Search for confirmatory findings in patient with a specific radiculopathy if surgery is contemplated. Occult back pain not responding to conservative treatment Rule out tumor or infection in appropriate patients
16	Anatomy
17	Anatomy
18	Disc disease After age 40, most adults have at least some desiccation and loss of height of lumber discs: Low signal on T2 images. Posterior or diffuse bulges and protrusions are common. Jelly-like nuclear material leaks out through tear in annular fibers.
19	Intervertebral disc anatomy
20	Glossary of disc pathology terms Herniation: nonspecific term subject to misinterpretation. Not recommended. Bulge: diffuse enlargement of disc area Very common Usually not clinically important May contribute to spinal stenosis Protrusion: nucleus pulposis pushes focally through fibers of annulus fibrosis Base wider than apex May focally impinge on nerve or thecal sac
21	Glossary of disc pathology terms Extrusion: nucleus material pushes out beyond posterior longitudinal ligament but remains in contact with disc space Apex wider than base Likely to impinge on nerve roots Sequestration: Disc fragment isolated from parent disc
22	Glossary of disc pathology terms Localizing terms: Central Paracentral Foraminal Lateral
23	Annular disc bulge
24	Broad based disc protrusion
25	Paramedian disc protrusion
26	Right paramedian disc protrusion
27	Foraminal Disc Extrusion
28	Even large disc extrusions will resolve spontaneously
29	Spondylosis Degenerative disease Disc desiccation, bulges and protrusions Ligamentum flavum hypertrophy Facet arthritis and hypertrophy Degenerative spondylolisthesis (seen in 7% of asx patients) Osteophytes All combine to cause stenosis of spaces that nerve roots pass through: Canal, lateral recess, neural foramen
30	Spaces for nerve roots
31	Facet joint arthritis
32	Spinal stenosis Symptoms Neurogenic claudication Pain relieved with sitting, bending forward Progressive pain +/- radiculopathy, cauda equina syndrome +/- low back pain No specific measurement to define it in the lumber spine. Many improved with nonsurgical therapy
33	Spinal stenosis Contributing factors: Disc bulges and protrusions Facet arthropathy Ligamentum flavum hypertrophy Posterior vertebral body osteophytes Anterior and lateral osteophytes generally not important Spondylolisthesis Not spondylolysis alone
34	Spondylosis (Degenerative Disease)
35	Spondylosis causing spinal stenosis
36	What does that report mean? Facet disease: Common in older patients May cause pain radiating to hip, simulating sciatica Predisposes to dynamic instability Contributes to spinal and foraminal stenosis Mild disc bulges or protrusions Very common incidental findings Focal sciatica Spinal stenosis only if large or in combination with other factors Usually not significant unless good correlation with sx.
37	What does that report mean? Look for key words and descriptions: “spinal stenosis”, “foraminal stenosis” Nerve root “displacement”, “compression” or “impingement” Is a specific root involved? Does it correlate with symptoms?
38	What to order: MRI or CT MRI generally preferred Contraindications to MRI? — CT is an acceptable substitute for disc and bony disease, but poor for infection or intrathecal tumor. MRI — IV contrast only for: Suspected infection Suspected tumor Post-operative spine Recurrent disc vs. scar tissue
39	Spinal and Epidural Infection High risk populations: Immunocompromised AIDS Transplant Chemotherapy Endocarditis or sepsis Postoperative patients especially with hardware Tuberculosis: not necessarily immune compromised
40	Bacterial discitis
41	Tuberculous spondylitis with epidural abscess
42	IV drug user– paraspinal abscess
43	Compression fracture: Benign or malignant? Often difficult to distinguish cause of acute compression fracture History of osteoporosis? Osteoporosis may indicate multiple myeloma in patient without risk factors. History of primary tumor? MRI good for survey of marrow at other levels to look for other metastases Bone scan may serve same function
44	Compression fracture: Acute or chronic? Many patients have unsuspected old compression fractures: Cheapest evaluation: check old films! Bone scan can prove a fracture is old May remain positive for up to two years In elderly, may not be positive in first day MRI can detect acute marrow edema
45	Compression Fracture—new or old? New Hypointense T1 Hyperintense T2 Easily missed if only T2 Sequence used Chronic Same marrow signal as other vertebral bodies on all pulse sequences
46	Metastatic disease On T1 weighted images, discs should be darker than marrow tissue Tumor brighter on T2 weighted images, enhances with contrast Exception—sclerotic prostate metastases
47	Review Questions
48	All of the following contribute to spinal stenosis except: Facet arthritis Spondylolysis Spondylolisthesis Disc protrusion Ligamentum flavum hypertrophy
49	Patients for whom early imaging is recommended: 35 year old with AIDS and back pain 35 year old mother of three with sciatica 70 year old with breast cancer and severe new back pain 45 year old man with severe back pain after moving furniture 65 year old with saddle anesthesia
50	All statements are true except: Disc protrusions commonly resolve spontaneously. MRI can reliably identify the level of nerve root involvement. CT scanning is appropriate for evaluation of suspected spinal stenosis or disc pathology. MRI is useful in distinguishing acute from chronic compression fractures.
51	Additional reading Brant-Zawadski MN et al Low Back Pain. What the clinician wants to know. Radiology 2000; 217:321-330. Schonstrom N, Willen J Imaging lumbar spinal stenosis. Radiologic Clin NA 2001;39(1):31-54 Stabler A, Reiser MF Imaging of spinal infection. Radiol Clin NA 2001; 39(1):115-136. McCall IW Lumbar herniated disks. Radiol Clin NA 2001;39(1):1293-1309
52	The End