Extradural Lesion, T2 Hyperintense, T1 Isointense

Bryson Borg, MD

DIFFERENTIAL DIAGNOSIS

Common

Intervertebral Disc Herniation
Synovial Cyst
Peridural Fibrosis
Epidural Fluid Collections
- Abscess, Epidural
- Hematoma, Epidural-Subdural (Acute)
Epidural Metastatic Disease
Neurofibroma
Schwannoma

Rare but Important

Primary Bone Tumor
- Plasmacytoma
- Lymphoma
- Chordoma
- Chondrosarcoma
- Giant Cell Tumor
- Ewing Sarcoma

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, depending on disc hydration
  - Herniations of the protrusion and extrusion subtypes most frequently hypointense relative to normal disc
  - Sequestered disc fragments often of moderate-to-high T2 signal
Synovial Cyst
- Circumscribed, fluid-filled structure
- Variable iso- or hypointensity on T1WI; centrally hyperintense on T2WI
- Adjacent/contiguous with a facet joint
- Cyst along ventral facet may impinge on thecal sac or nerve root
- Seen with degenerative facet changes
Peridural Fibrosis
- Epidural scar formation following spinal surgery
- Normal post-operative finding
- Infiltrative morphology, rarely mass-like
- Isointense T1; variable T2 signal, usually hyperintense relative to disc material
- May surround nerve root
- Can only be differentiated from recurrent disc herniation on post-contrast imaging
  - Peridural fibrosis will homogeneously enhance, blending into extradural fat on non-FS T1WI
Abscess, Epidural
- May be associated with disc space infection or instrumentation/direct inoculation
- Contents typically approximate fluid signal on T1/T2WI
  - Increased T1 signal (isointense) may occur secondary to increased protein content
- Marked peripheral enhancement typical on post-contrast imaging
Hematoma, Epidural-Subdural (Acute)
- May be spontaneous or associated with trauma or instrumentation
- Signal varies with the age of the hemorrhage
  - Acute hemorrhage (oxyhemoglobin) iso- or mildly hypointense on T1WI, hyperintense on T2WI
- Minimal or no enhancement on post-contrast imaging
Epidural Metastatic Disease
- Enhancing soft tissue mass, may be multiple
- Most often associated with epidural extension from a vertebral metastasis
- May also occur with transforaminal spread from a paraspinal or posterior mediastinal tumor
Neurofibroma
- Enhancing nodular, fusiform, or dumbbell mass associated with a nerve root
- Epidural neurofibroma typically intraforaminal or transforaminal
- May be associated with vertebral scalloping, thinning/remodeling of pedicles
- Most (90%) solitary, nonsyndromic
- May be multiple, extensive; associated with plexiform neurofibromas (neurofibromatosis type 1)
Schwannoma
- Enhancing nodular, fusiform, or dumbbell mass associated with a nerve root
- Most schwannoma intradural; epidural schwannoma typically intraforaminal or transforaminal
- Not reliably distinguished from solitary neurofibroma

Helpful Clues for Rare Diagnoses

Plasmacytoma
- Solitary plasma cell tumor, osteolytic tumor, ± compression fracture, ± extraosseous extension
- Often indistinguishable from lytic metastases
Lymphoma
- Enhancing epidural mass or epidural extension from a vertebral lesion
- Often indistinguishable from metastases
- Spinal lymphoma may also manifest with leptomeningeal or intramedullary lesions
Chordoma
- Arises from notochord remnants: Midline, osteolytic tumor
- Sacrococcygeal location most common, followed by clivus; vertebral lesion rather uncommon
- May extend into epidural/paraspinal spaces
- Heterogeneous iso- or hypointense on T1WI; marked hyperintensity on T2WI
- Variable enhancement
Chondrosarcoma
- Destructive tumor, chondroid matrix
- Iso- or hypointense on T1WI; marked hyperintensity on T2WI
- Heterogeneous enhancement
Giant Cell Tumor
- Lytic, expansile vertebral body lesion; narrow zone of transition
- May extend into epidural/paraspinal spaces
- Heterogeneous iso- or hypointense on T1WI; heterogeneous hyperintensity on T2WI
  - Areas of low-to-intermediate T2 signal may reflect areas of high collagen content and hemosiderin deposition
- Propensity to extend across sacroiliac joint & disc space is unusual for other lesions and may simulate infection
Ewing Sarcoma
- Destructive tumor
- Iso- or hypointense on T1WI; moderate to hyperintense signal on T2WI
- Paraspinal soft tissue mass often a feature of spinal Ewing sarcoma