Extradural Lesion, T1 Hyperintense
Bryson Borg, MD
DIFFERENTIAL DIAGNOSIS
Common
Normal Epidural Fat
Epidural Lipomatosis
Hematoma, Epidural-Subdural
Less Common
OPLL (with Fatty Marrow)
Extraosseous Hemangioma
Lipomyelomeningocele
Terminal Lipoma
Rare but Important
Angiolipoma
Metastatic Melanoma
ESSENTIAL INFORMATION
Helpful Clues for Common Diagnoses
Normal Epidural Fat
Usually most conspicuous dorsally in the thoracic region on midline sagittal slices
Key finding is lack of significant mass effect on the thecal sac
Epidural Lipomatosis
Overabundance of epidural fat, most commonly affecting thoracic and lumbar spine
Resulting compression of the thecal sac leads to a Y-shaped or trefoil cross section
May be associated with prolonged steroid administration or with hypercortisolism
Hematoma, Epidural-Subdural
Actual signal characteristics depend on hematoma age; methemoglobin (subacute) hyperintense on T1WI
Can be clearly differentiated from epidural fat with frequency-selective fat-suppressed sequence
Helpful Clues for Less Common Diagnoses
OPLL (with Fatty Marrow)
Always ventral to thecal sac, mostly in cervical spine
OPLL will be most reliably defined on CT
Lipomyelomeningocele
Lumbosacral dysraphism
Everted elements of neural arch
Caudal fatty mass, contiguous with neural placode of a tethered, dysraphic cord; disjunction protrudes through the dysraphic defect
Skin-covered (closed spinal dysraphism)
Often discovered in infancy, but can be occult and come to attention during adolescence or adulthood
Terminal Lipoma
Lipoma of cord terminus or filum, often associated with tethered cord
Lipoma extends through caudal spondyloschisis, becomes confluent with subcutaneous fat
Not associated with myeloschisis: Represents disorder of regressive differentiation rather than of primary neurulation
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