Extradural Lesion, T2 Hypointense, T1 Hypointense

Bryson Borg, MD

DIFFERENTIAL DIAGNOSIS

Common

Intervertebral Disc Herniation
Endplate Osteophyte
Facet Osteophyte
Ossification Ligamentum Flavum
OPLL
Epidural Gas
Metal Artifact

Rare but Important

Epidural AVF

ESSENTIAL INFORMATION

Helpful Clues for Common Diagnoses

Intervertebral Disc Herniation
- Most common epidural lesion in adult population
- Intermediate-to-low T1 signal
- Variable T2 signal, hyperintense signal can be seen with annular fissures and sequestrations
Endplate Osteophyte
- Endplate osteophyte formation commonly accompanies degenerative disc disease
- May be difficult to distinguish osteophyte from a disc herniation on MR; NECT can supplement evaluation
Ossification Ligamentum Flavum
- Enlargement of ligamentum flavum causing variable posterolateral encroachment on the thecal sac
- Best conspicuity of calcifications on NECT
- If sufficiently ossified, may produce marrow space with hyperintensity on T1WI
- Idiopathic, probably related to hydroxyapatite or calcium pyrophosphate deposition
- May observe changes of DISH or OPLL elsewhere in spine
OPLL
- Idiopathic condition, resulting in calcification and thickening of the posterior longitudinal ligament
- Most common in the cervical spine, can involve upper thoracic
- Variable encroachment on the ventral spinal canal
- If sufficiently ossified, may produce a marrow space with hyperintensity on T1WI
Epidural Gas
- Routinely seen in the acute post-operative period
- Can occur from
  - “Vacuum” disc phenomenon extending into disc herniation
  - “Vacuum” joint phenomenon extending into facet synovial cyst
Metal Artifact
- Epidural catheters
- Spinal cord stimulators
- Spinal fusion hardware
- Displaced intervertebral devices

Image Gallery

Sagittal T1WI MR shows a large disc extrusion at L4-5. Extruded disc material is similar in signal to the remainder of the intervertebral disc on T1WI.

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