July 11, 2013

Lipoma of Filum Terminale

Sagittal T1W image shows a T1 hyperintense mass at the filum terminale and a thin fatty strand extending from the tip of the conus medullaris to the coccyx.
Sagittal T2W image with fat suppression demonstrates signal loss of the mass, indicating presence of fat.


  • Abnormal retrogressive differentiation of pleuripotential cells found in distal caudal mass
  • Mostly incidental, found in 5% of lumbar spine MRI but may be associated with tight filum terminale syndrome
  • Fat is clearly separable from nerve roots and conus medullaris that terminates at above L2 level
  • Fat intensity mass (hyperintense T1, hyperintense T2, and progressive lower signal on greater T2 weighting)
  • Can be intradural or extradural
  • Intradural fatty filum is fusiform, tapering down toward where the filum pierces the dura
  • Extradural fatty filum is often larger, more diffuse, elevating/distorting distal thecal sac

Atlas SW. Magnetic resonance imaging of the brain and spine, 4th edition, 2009

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