Intradural/Extramedullary Lesion, T1 Hyperintense

Jeffrey S. Ross, MD

DIFFERENTIAL DIAGNOSIS

Common

Less Common

Rare but Important

ESSENTIAL INFORMATION

Helpful Clues for Common Diagnoses

Metal Artifact
- MR ⇒ geometric distortion + signal loss secondary to dephasing
- Minimize with FSE, larger FOV, higher bandwidth, small voxel, orientation of frequency encode direction
- Minimize pedicle screw artifact by orienting frequency encode gradient parallel to screw long axis, using FSE technique
Filum Terminale Fibrolipoma
- T1WI shows small linear focus of fat, with normal conus position and morphology
- Incidental in 4-6% of autopsy subjects
- Intraspinal lipoma if larger lesion and filum > 2 mm in thickness
Lipoma
- Spinal lipoma intimately associated with dorsal spinal cord (intradural) or distal cord/filum insertion (terminal)
- Hyperintense (T1WI) intradural mass
- Use frequency selective fat suppression if unsure of composition of hyperintense mass
Subarachnoid Hemorrhage
- Intradural collection hyperintense on T1WI, predominantly hypointense on T2WI or gradient-echo imaging
- Subarachnoid shows fluid-fluid level
- Subdural shows well-defined outer dural margin, lobulated inner margin
Lipomyelomeningocele
- Subcutaneous fatty mass contiguous with neural placode/lipoma via posterior dysraphism
- Cord always tethered
- Cutaneous stigmata (50%); hemangioma, dimple, dermal sinus, skin tag, hairy patch

Helpful Clues for Less Common Diagnoses

Dermoid and Epidermoid Tumors
- Epidermoid ⇒ nonenhancing, CSF signal-like intradural mass within cauda equina
  - Look for dermal sinus association
- Dermoid shows heterogeneous mass with mixed signal (fat)