Back Pain Imaging

Back Pain Imaging

Adam Guttentag M.D.

Wasted time?

Radiology departments do lots of imagingfor low back pain.

X-rays, CT, MRI etc.

How much makes a difference?

Studies show advanced imaging in acuteback pain and sciatica doesn’t changeoutcomes, but improves diagnosticconfidence.

Causes of back pain and sciatica

Paraspinal musclesand ligaments

Synovial joints:

Facet and sacroiliacjoints

Disc disease

Tear of annulusfibrosis

Specific nerve rootimpingements

Spondylosis

Spinal stenosis

Foraminal stenosis

Bone disease

Tumor

Fracture

Infection

Epidural abscess

discitis

Acute Back Pain

2nd most common complaint to primarycare physician

>75% of adults will suffer it at some time.

90% will resolve without intervention (orimaging), most without a specific dx.

Among patients with sciatica, only <10%will need surgery.

Whom to image?

Back pain imaging—false positives

Most adults over 40 will have degenerativechanges on x-rays

MRI shows disc pathology in the majorityof adults

Many asymptomatic people have discbulges and protrusions.

So, imaging is likely to result in anabnormal report.

But correlation between radiographicfindings and clinical symptoms is poor.

When to image?

When to image in patients with acuteback pain?

Most authorities suggest conservativetreatment for 4-6 weeks unless there are“red flags”:

Look for historical and physical findings that raiseclinical question of infection, tumor, or seriousneurological impairment

Even positive findings of degenerative diseaselike disc extrusions and spinal stenosis are noturgent and will be treated conservatively at first.

“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

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

Diskography

Radiography

AP and lateral films

Oblique films

Flexion / extension films

Radiography

Diagnoses that can be made on AP andlateral:

Spondylolisthesis

Compression fracture

SI joint disease

Disc degeneration

Facet arthritis

Tumor

Infection in disc space

Discitis

Radiography

Diagnosis bestmade onoblique films:

Spondylolysis

Facet arthritis

Foraminalstenosis(cervical spine)

Facet joints

Radiography

Diagnosis made with flexion / extensionfilms:

instability

Spondylolysis

Stress fracture through pars interarticularis

If bilateral, can cause spondylolisthesis

spondylolosthesis

spondylolysis

Sagittal reformatted CT

Cross Sectional Imaging: CT and MRIWhy?

Confirm extent of degenerative disease and spinalstenosis.

Search for confirmatory findings in patient with aspecific radiculopathy if surgery is contemplated.

Occult back pain not responding to conservativetreatment

Rule out tumor or infection in appropriate patients

MRI

IV contrast only in:

Suspected infection

Suspected tumor

Post-operative spine

Recurrent disc vs. scar tissue

Contraindications to MRI—CT is anacceptable substitute for disc and bonydisease, but poor for infection or intrathecaltumor.

Anatomy

Conusmedullaris

Caudaequina

Anatomy

Nucleuspulposis

Nerve rootin foramen

Facet joint

disc

Nerve rootin foramen

Ligamentumflavum

Disc disease

After age 40, most adults have at leastsome desiccation and loss of height oflumber discs:

Low signal on T2 images.

Posterior or diffuse bulges and protrusions arecommon.

Jelly-like nuclear material leaks out through tearin annular fibers.

Intervertebral disc anatomy

Annular fibers

Nucleuspulposis

Glossary of disc pathology terms

Herniation: nonspecific term subject tomisinterpretation.

Not recommended.

Bulge: diffuse enlargement of disc area

Very common

Usually not clinically important

May contribute to spinal stenosis

Protrusion: nucleus pulposis pushes focallythrough fibers of annulus fibrosis

Base wider than apex

May focally impinge on nerve or thecal sac

Glossary of disc pathology terms

Extrusion: nucleus material pushes out beyondposterior longitudinal ligament but remains incontact with disc space

Apex wider than base

Likely to impinge on nerve roots

Sequestration: Disc fragment isolated from parentdisc

Glossary of disc pathology terms

Localizing terms:

Central

Paracentral

Foraminal

Lateral

Annular disc bulge

Disc bulges diffusely

Broad based disc protrusion

Paramedian disc protrusion

Normal right L5 root

Displaced left L5 root

This should correlate with a leftL5 radiculopathy.

Disc Extrusion

Axial T2

Sag T1

Sag T2

Foraminal Disc Extrusion

Foraminal Fat Obliterated

Normalforamina

Even large disc extrusions will resolvespontaneously

Several months later

Large extruded disc

Spondylosis

Degenerative disease

Disc dessication, bulges and protrusions

Ligamentum flavum hypertrophy

Facet arthritis and hypertrophy

Degenerative spondylolisthesis (seen in 7% of asxpatients)

Osteophyes

All combine to cause stenosis of spaces thatnerve roots pass through:

Canal, lateral recess, neural foramen

Spaces for nerve roots

Nerve root in lateral recess

Neural foramen

Cauda equina roots in spinal canal

Facet joint arthritis

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 lumberspine.

Many improved with nonsurgical therapy

Spinal stenosis

Contributing factors:

Disc bulges and protrusions

Facet arthropathy

Ligamentum flavum hypertrophy

Posterior vertebral body osteophytes

Anterior and lateral osteophyes generally notimportant

Spondylolisthesis

Not spondylolysis alone

Spondylosis(Degenerative Disease)

Sag T2

Axial T2

Axial CT

Annular disc bulge and facet arthropathy causespinal stenosis

Spondylosis causing spinal stenosis

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 withother factors

Usually not significant unless good correlation withsx.

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?

Spinal and Epidural Infection

High risk populations:

Immunocompromised

AIDS

Transplant

Chemotherapy

Endocarditis or sepsis

Postoperative patients especially with hardware

Tuberculosis: not necessarily immunecompromised

Bacterial discitis

T1 Sag

T1 Axial With GD

T2 Sag

Tuberculous spondylitis withepidural abscess

T1 with Gd

Enhancingvertebral body

Non-enhancingfluid in discspace andepidural space

IV drug user– paraspinal abscess

T1 unenhanced

T1 enhanced

T2 unenhanced

Compression fracture:Benign or malignant?

Often diffucult to distinguish cause of acutecompression fracture

History of osteoporosis?

Osteoporosis may indicate multiple myeloma inpatient without risk factors.

History of primary tumor?

MRI good for survey of marrow at other levels tolook for other metastases

Bone scan may serve same function

Compression fracture:Acute or chronic?

Many patients have unsuspected oldcompression 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

Compression Fracture—new or old?

•New

•Hypointense T1

•Hyperintense T2

Easily missed if only T2Sequence used

•Chronic

•Same marrow signalas other vertebralbodies on all pulsesequences

Metastatic disease

On T1 weighted images,discs should be darkerthan marrow tissue

Tumor brighter on T2weighted images,enhances with contrast

Exception—scleroticprostate metastases

Questions

All of the following contribute tospinal stenosis except:

Facet arthritis

Spondylolysis

Spondylolisthesis

Disc protrusion

Ligamentum flavum hypertrophy

Patients for whom early imaging isrecommended:

35 year old with AIDS and back pain

35 year old mother of three with sciatica

70 year old with breast cancer and severe newback pain

45 year old man with severe back pain aftermoving furniture

65 year old with saddle anesthesia

All statements are true except:

Disc protrusions commonly resolvespontaneously.

MRI can reliably identify the level of nerve rootinvolvement.

CT scanning is appropriate for evaluation ofsuspected spinal stenosis or disc pathology.

MRI is useful in distinguishing acute fromchronic compression fractures.

Reading

Brant-Zawadski MN et al Low Back Pain. What theclinician wants to know. Radiology 2000; 217:321-330.