Tethered Cord

  • Etiology: Failure of closure of posterior neural tube
  • Imaging US:
    — Low position of conus medullaris (conus should be above L2-L3 disc space in newborn)
    — Fixed nerve roots (nerve roots that remain anti-dependent in spinal canal
    — Decreased or absent motion of cauda equina
  • Imaging MRI:
    — Low position of conus medullaris (conus should be above L2-L3 disc space in newborn)
    — Thick filum terminale
    — Look for secondary signs of cord tethering on the scan – scoliosis or syrinx or fecal and urinary retention
  • Note: Can still have tethered cord if conus above L2-L3 disc space and there is lipoma of the filum terminale
  • DDX:
  • Complications:
  • Treatment: Surgical
  • Clinical:
    — Occult skin covered spinal dysraphism
    — Most mild dysraphism
    — Associated with a sacral dimple or hair patch at sacrum
    — Note: Most simple sacral dimples do not have an associated spinal cord abnormality

Radiology Cases of Tethered Cord

Radiology Cases of Normal Position of the Conus Medullaris

Spine US of normal position of the conus medullaris
Sagittal US of the lumbar spine shows the conus medullaris to be in a normal position at the L2 vertebral body.
US and MRI of tethered cord
Sagittal US of the spine (above) shows an extremely low lying conus which appears to extend as far as S1. Sagittal T2 MRI without contrast of the spine (below) shows the conus to be located around L5-S1.
MR of normal position of the conus medullaris
Sagittal T2 MRI of the lumbar spine (left) shows the tip of the conus medullaris to lie at the level of L1-L2. Sagittal T1 without contrast MRI (right) shows the low signal intensity posterior dermal sinus tract running linearly from the sacral dimple at the skin to the coccyx.

Radiology Cases of Tethered Cord and Lipoma of the Filum Terminale

MRI of lipoma of the filum terminale and tethered cord
Sagittal T1 MRI without contrast of the lumbar spine (left) shows hyperintense signal in the conus medullaris which lies low in position at the level of L2-L3. Axial T1 MRI through the conus (right) better shows the hyperintense signal in the conus which is the same signal intensity as the subcutaneous fat.

Radiology Cases of Tethered Cord

MRI of tethered cord
Sagittal T1 (left) and T2 (right) MRI of the lumbar spine shows a low-lying conus medullaris of the spinal cord which terminates at S1. The T11/T12 vertebral body areas of low signal intensity on T1 and high signal intensity on T2 were felt to be due to aggressive Schmorl nodes as the patient had no clinical signs of infection.

Clinical Cases of Tethered Cord

Clinical Cases of Normal Position of the Conus Medullaris

Clinical image of a dermal sinus tract
Clinical image shows a sacral dermal sinus tract in the midline just above the gluteal cleft.

Clinical Cases of Tethered Cord

Clinical image of a sacral dimple
Clinical image shows a round sacral dimple in the midline just above the gluteal cleft.