NEURO-RADIOLOGY

RAJ REDDYNeurosurgery

Prince of Wales Hospital

SPINE

Objectives

Review spine anatomy on X-ray, CT and MRI Approach to interpretation of imaging Differential diagnoses for common spine

lesions

Imaging Modalities

Basic Imaging Types

X-ray CT (Computed Tomography) MRI (Magnetic Resonance Imaging) Angiography

X-ray

Limited Use Evaluation of:

Bones (fractures) Calcification

Computed Tomography

http://fitsweb.uchc.edu/student/selectives/TimHerbst/intro.htm

Computed Tomography (CT)

Tomography Imaging in sections, or slices

Computed Geometric processing used to reconstruct an

image Computerized algorithms

Computed Tomography

Uses X-rays Dense tissue, like bone, blocks x-rays Gray matter weakens (attenuates) the x-rays Fluid attenuates even less

A computerized algorithm (filtered backprojection) reconstructs an image of each slice

CT Image Formation

X-ray detectorX-ray

X-ray tube

CT Image Formation

Backprojection

CT Image Reconstruction – 6 Slices

CT Image Reconstruction – 12 Slices

CT Image Reconstruction – Final

Magnetic Resonance Imaging

What is MR?

Not an X-ray, electromagnetic Electromagnetic field aligns all the

protons in the brain Radiofrequency pulses cause the

protons to spin Amount of energy emitted from the spin

is proportional to number of protons in the tissue

No ferromagnetic objects

Angiography

Angiography

Real time X-ray study Catheter placed through femoral artery is

directed up aorta into the cerebral vessels Radio-opaque dye is injected and vessels are

visualized Gold standard for studying cerebral vessels.

Angiography

AP Right ICA Lateral Right ICA

Angiography

AP Right Vertebral

Planes of Section

Axial (transverse) Sagittal Coronal Oblique

Anatomy

Radiographic Anatomy

Cervical Spine – AP View

Cervical Spine – Lateral View

Cervical Spine – Open-Mouth (Dens) View

Cervical Spine – Oblique View

Lumbar Spine – AP View

Lumbar Spine – Lateral View

Approach to Xrays

Approach to Spine Imaging

A – adequacy/alignment

B – bone

C – cord/canal/cartilage

D – disc

E – extras

C7-T1

Alignment

1. prevertebral 2. anterior spinal 3. posterior spinal 4. spino-laminar

Cartilage Predental Space

should be no more than 3 mm in adults and 5 mm in children

Increased distance may indicate fracture of odontoid or transverse ligament injury

Cartilage Disc Spaces

Should be uniform

Assess spaces between the spinous processes

Soft tissue Nasopharyngeal space

(C1) - 10 mm (adult) Retropharyngeal space

(C2-C4) - 5-7 mm Retrotracheal space

(C5-C7) - 14 mm (children), 22 mm (adults)

Extremely variable and nonspecific

CT Anatomy

CT

MRI Anatomy

Compartments of the Spinea. Intradural, intramedullaryb. Intradural, extramedullaryc. Extradural, extramedullary

a. c.b.

…

Pathology

Spine Pathology

Trauma Degenerative disease Tumors and other masses Inflammation and infection Vascular disorders Congenital anomalies

Trauma

Evaluating Trauma Fracture – plain film / CT Dislocation – plain film / CT Ligamentous injury – MRI Cord injury – MRI Nerve root avulsion – MRI

To x-ray or not to x-ray? 13 million trauma

patients at risk for cervical spine injury

very low incidence of cervical spine fracture

In alert and stable trauma patients:

x-rays performed on 69% CT performed in 5% acute injury in 2.6% stabilization in 2.2%

Stiell IG et al. The Canadian C-Spine Rule versus NEXUS in Patients with Trauma. N Engl J Med. 2003.

NEXUS C-Spine Rules

Canadian C-Spine Rules (CCR)

Stiell IG. The CCR in Alert and Stable Trauma Patients. JAMA. 2001.

Which one is better?NEXUS Pro: easy to use Con: poor sensitivity and

specificity (90.7% and 36.8%)

Con: more x-rays (67%)

CCR Pro: great sensitivity and specificity (99.4%

and 45.1%) Pro: less x-rays (55.9%) Con: more difficult to remember and use

Stiell IG et al. The Canadian C-Spine Rule versus NEXUS in Patients with Trauma. N Engl J Med. 2003.

Plain film findings may be very subtle or absent!

Anterolisthesis of C6 on C7

(Why?)

CTFractures of C6 left pedicle and lamina

CT – 2D Reconstructions

Acquire images axially…

…reconstruct sagittal / coronal

26M MVA

Vertebral body burst fx with retropulsion into spinal canal

2D Reformats

Vertebral Artery Dissection/Occlusion Secondary to C6 Fracture

Hyperflexion fx with ligamentous disruption and

cord contusion

Nerve root avulsion

Axial Coronal Sagittal

Degenerative Disease

Degenerative Disc (and Facet Joint) Disease

Foraminal stenosis

Thickening/Buckling of Ligamentum

Flavum

Degenerative Disc (and Facet Joint) Disease

Degenerative Disc (and Facet Joint) Disease

Lumbar Spinal Stenosis

Lumbar Spinal Stenosis

Lumbar Spinal Stenosis

Lumbar Spinal Stenosis

Lumbar Spinal Stenosis

Lumbar Spinal Stenosis

Disc bulge, facet hypertrophy and flaval ligament thickening frequently combine to cause central spinal stenosis

Note the trefoil shape of stenotic spinal canal

Lumbar Spinal Stenosis

Disc bulge, facet hypertrophy and flaval ligament thickening frequently combine to cause central spinal stenosis

Note the trefoil shape of stenotic spinal canal

Foraminal StenosisNeural

foramen

Cervical Spinal Stenosis

MRI - Degenerative Disc Disease

20-40 36% have degenerated disc 50 85-95% have degenerated disc 60-80 98% have degenerated disc <60 20% have asymptomatic disc herniation

Age:

Conclusion: Abnormal findings on MRI frequently DO NOT relate to symptoms (and vice versa) !

MRI – Herniated Disc Levels 85-95% at L4-L5, L5-S1 5-8% at L3-L4 2% at L2-L3 1% at L1-L2, T12-L1 Cervical: most common C4-C7 Thoracic: 15% in asymptomatic pts. at

multiple levels, not often symptomatic

Annular

Adapted from: “Nomenclature and Classification of Lumbar Disc Pathology: Recommendations of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology,” 2001.

Adapted from: “Nomenclature and Classification of Lumbar Disc Pathology: Recommendations of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology,” 2001.

Adapted from: “Nomenclature and Classification of Lumbar Disc Pathology: Recommendations of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology,” 2001.

Adapted from: “Nomenclature and Classification of Lumbar Disc Pathology: Recommendations of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology,” 2001.

Adapted from: “Nomenclature and Classification of Lumbar Disc Pathology: Recommendations of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology,” 2001.

Protrusion Extrusion Extrusion

Adapted from: “Nomenclature and Classification of Lumbar Disc Pathology: Recommendations of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology,” 2001.

Protrusion Protrusion w/migration

Protrusion w/migration +

sequestration

Adapted from: “Nomenclature and Classification of Lumbar Disc Pathology: Recommendations of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology,” 2001.

Abnormal Disc

Bulge

Symmetric Asymmetric

Herniation

Broad-based Focal

Extrusion Protrusion

Sequestered Migrated Neither

> 180º< 180º

< 90º90º–180º

No waistWaist*

Adapted from: “Nomenclature and Classification of Lumbar Disc Pathology: Recommendations of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology,” 2001.

*(In any plane)

Central Disc Protrusion

L5-S1 Disc Extrusion Into Lateral Recess with Impingement of R S1 Nerve Root

L-S1DiscR-S1

Schmorl’s Nodes

Cervical Radiculopathy

Lumbosacral Radiculopathy (Sciatica)

Important: A herniated disc at (e.g.) L4-5 may impinge either the L4 or L5 nerve roots!

L5-S1 Disc Extrusion Into Lateral Recess with Impingement of R S1 Nerve Root

L-S1DiscR-S1

Spondylolysis / Spondylolisthesis

Confusing “Spondy-” Terminology

• Spondylosis = “spondylosis deformans” = degenerative spine

• Spondylitis = inflamed spine (e.g. ankylosing, pyogenic, etc.)

• Spondylolysis = chronic fracture of pars interarticularis with nonunion (“pars defect”)

• Spondylolisthesis = anterior slippage of vertebra typically resulting from bilateral pars defects

• Pseudospondylolisthesis = “degenerative spondylolisthesis” (spondylolisthesis resulting from degenerative disease rather than pars defects)

Tumors and Other Masses

Extradural = outside the thecal sac (including vertebral bone lesions)

Intradural / extramedullary = within thecal sac but outside cord

Intramedullary = within cord

Classification of Spinal Lesions

Herniated disc Vertebral hemangioma Vertebral metastasis Epidural abscess or hematoma Synovial cyst Nerve sheath tumor (also intradural/extramedullary)

Neurofibroma Schwannoma

Common Extradural Lesions

Nerve sheath tumor (also extradural) Neurofibroma Schwannoma

Meningioma

Drop Metastasis

Common Intradural Extramedullary Lesions

Astrocytoma Ependymoma Hemangioblastoma Cavernoma Syrinx Demyelinating lesion (MS) Myelitis

Common Intramedullary Lesions

Classification of Spinal Lesions

Extradural IntramedullaryIntraduralExtramedullaryDuraCord

Extradural: Vertebral Body Tumor

Extradural: Vertebral Metastases

T2 (Fat Suppressed) T1 T1+C (fat suppressed)

Extradural: Vertebral Metastases

T2 (Fat Suppressed) T1 T1+C (fat suppressed)

?

Vertebral Metastases vs. Hemangiomas

Hemangiomas (Benign, usually asymptomatic, commonly incidental):

Bright on T1 and T2 (but dark with fat suppression) Enhancement variable

Metastases:

Dark on T1, Bright on T2 (even with fat suppression) Enhancement

Vertebral Hemangiomas

Diffusely T1-hypointense marrow signal may represent widespread vertebral metastases as in this patient with prostate Ca

This can also be seen in the setting of anemia, myeloproliferative disease, and various other chronic disease states

Extradural: Vertebral Metastases

Extradural: Epidural Abscess

Extradural: Nerve Sheath Tumor(Schwannoma)

Intradural Extramedullary: Meningioma

Intradural Extramedullary: Meningioma

Intradural Extramedullary: Nerve Sheath Tumor(Neurofibroma)

Intradural Extramedullary: “Drop Mets”

T2 T1 T1+C

Intradural Extramedullary: “Drop Mets”

Intradural Extramedullary: Arachnoid Cyst

T2 T1

Intramedullary: Astrocytoma

Intramedullary: Astrocytoma

Intramedullary: Cavernoma

Intramedullary: Ependymoma

Seen with:• congenital lesions

• Chiari I & II• tethered cord

• acquired lesions• trauma• tumors• arachnoiditis

• idiopathic

Intramedullary: Syringohydromyelia

Seen with:• congenital lesions

• Chiari I & II• tethered cord

• acquired lesions• trauma• tumors• arachnoiditis

• idiopathic

Intramedullary: Syringohydromyelia

Confusing “Syrinx” Terminology

• Hydromyelia: Fluid accumulation/dilatation within central canal, therefore lined by ependyma

• Syringomyelia: Cavitary lesion within cord parenchyma, of any cause (there are many). Located adjacent to central canal, therefore not lined by ependyma

• Syringohydromyelia: Term used for either of the above, since the two may overlap and cannot be discriminated on imaging

• Hydrosyringomyelia: Same as syringohydromyelia

• Syrinx: Common term for the cavity in all of the above

Infection and Inflammation

Infectious Spondylitis / Diskitis

Common chain of events (bacterial spondylitis): 1. Hematogenous seeding of subchondral VB2. Spread to disc and adjacent VB3. Spread into epidural space epidural abscess4. Spread into paraspinal tissues psoas abscess5. May lead to cord abscess

Infectious Spondylitis / Diskitis

T2 T1 T1+C T1+C

Infectious Spondylitis / Diskitis

Pyogenic Spondylitis / Diskitis with Epidural Abscess

T1

T2

T1 + C

Spinal TB (Pott’s Disease)

• Prominent bone destruction• More indolent onset than pyogenic• Gibbus deformity• Involvement of several VB’s

Spinal TB (Pott’s Disease)

• Prominent bone destruction• More indolent onset than pyogenic• Gibbus deformity• Involvement of several VB’s

Transverse Myelitis

Inflamed cord of uncertain cause Viral infections Immune reactions IdiopathicMyelopathy progressing over hours to weeksDDX: MS, glioma, infarction

Multiple Sclerosis

Inflammatory demyelination eventually leading to gliosis and axonal loss

T2-hyperintense lesion(s) in cord parenchyma

Typically no cord expansion (vs. tumor); chronic lesion may show atrophy

Multiple Sclerosis

Inflammatory demyelination eventually leading to gliosis and axonal loss

T2-hyperintense lesion(s) in cord parenchyma

Typically no cord expansion (vs. tumor); chronic lesion may show atrophy

Cord Edema

As in the brain, may be secondary to ischemia (e.g. embolus to spinal artery)

or venous hypertension (e.g. AV fistula)

Spine Imaging Guidelines1. Uncomplicated LBP usually self-limited, requires no imaging

2. Consider imaging if: • Trauma• Cancer• Immunocompromise / suspected infection• Elderly / osteoporosis• Significant neurologic signs / symptoms

3. Back pain with signs / symptoms of spinal stenosis or radiculopathy, no trauma:

Start with MRI; use CT if:

• Question regarding bones or surgical (fusion) hardware

• Resolve questions / solve problems on MRI (typically use CT myelography)

• MRI contraindicated

4. Begin with plain films for trauma; CT to solve problems or to detail known

fractures; MRI to evaluate soft-tissue injury (ligament disruption, cord contusion)

5. MRI for sx of radiculopathy, cauda equina syn, cord compression, myelopathy

6. Fusion hardware is safe for MRI but may degrade image quality; still worth a try

7. Indications for IV contrast in MRI:

• Tumor, infection, inflammation (myelitis), any cord lesion

• Post-op L-spine (discriminate residual/recurrent disk herniation from scar)

8. Emergent or scheduled? Emergent only if immediate surgical or radiation therapy

decision needed (e.g. cord compression, cauda equina syndrome)

9. Difficult to image entire spine in detail; target study to likely level of pathology

10. CT chest/abdomen/pelvis includes T-L spine (no need to rescan trauma pts*)* If image data still on scanner (24-48 hours)

Spine Imaging Guidelines