29.1 Case Presentation

29.2 Imaging Analysis

Lumbosacral spine MRI from a 9-year-old male patient with nonspecific back pain was performed. Sagittal T1-weighted (T1w; ▶ Fig. 29.1a), sagittal short tau inversion recovery (STIR; ▶ Fig. 29.1b), axial T1w (▶ Fig. 29.1c), and axial T2-weighted (T2w) with fat suppression (▶ Fig. 29.1d) images. An intrathecal linear hyperintensity is seen in T1w sagittal and axial images (arrows in ▶ Fig. 29.1a,c), in close relationship with the filum terminale; its high T1w signal intensity is suppressed in the series with fat saturation (arrows in ▶ Fig. 29.1b,d). Note the normal morphology and position of conus medullaris (asterisk in ▶ Fig. 29.1b) with tip located at the superior end plate of L2 level (arrowhead in ▶ Fig. 29.1b).

29.3 Differential Diagnosis

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  Filum terminale lipoma:

  
  
  
  
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    It is seen as a linear hyperintensity within the filum terminale on T1w images, 1- to 5-mm wide and of variable length, and follows fat signal intensity in all MRI sequences. ^{1 , 2 , 3}

  
  
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  Tethered cord with terminal lipoma:

  
  
  
  
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    The cord extends abnormally inferiorly than the normal level of mid-L2, and there is a thick lipoma at its caudal termination.

    
    
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    Indistinct cord termination with a smooth transition between conus and filum. ^{4 , 5}