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Tethered Spinal Cord


KEY FACTS

Terminology

  • Synonyms: Tethered cord syndrome (TCS), tight filum terminale syndrome

Imaging

  • Stretched, thinned cord with low-lying conus, thickened filum

  • ± fibrolipoma/terminal lipoma, dysraphism, vertebral segmentation anomalies

  • ↓ spinal cord motion

Top Differential Diagnoses

  • Normal variant low-lying conus

  • Open or closed spinal dysraphism

  • Postsurgical low-lying conus

Pathology

  • Tethering stretches nerve fibers, arterioles, and venules → impaired oxidative metabolism of conus and nerve roots → syringohydromyelia, myelomalacia

  • Tethered filum histologically abnormal, even if conus terminates at normal level

Clinical Issues

  • Low back and leg pain, gait and sensory abnormalities, urinary bladder dysfunction

  • Symptomatic presentation most common during rapid somatic growth (adolescent growth spurt, school age 4-8 years), or secondary to kyphosis (elderly)

Diagnostic Checklist

  • TCS is clinical diagnosis; imaging role is detection of low-lying conus/thick filum, associated anatomic abnormalities for surgical decision making

  • Clinical tethering may be present despite normal conus level

  • Measure filum thickness at L5/S1; stretching at more rostral levels may erroneously thin filum into “normal” size range

Sagittal graphic of the lumbosacral spine depicts composite tethered cord syndrome (TCS) findings of low-lying, hydromyelic tethered cord with thickened filum and fibrolipoma inserting into a terminal lipoma that is contiguous with subcutaneous fat through dorsal dysraphism.

Sagittal T2WI MR (clinical TCS) demonstrates an elongated low-lying spinal cord extending to the S2 level, where it ends in a small terminal lipoma
. Focal sacral posterior dysraphism is also present.

Sagittal T1WI MR (clinical TCS symptoms) confirms an elongated low-lying spinal cord extending to the S2 level and ending in a small terminal lipoma
. Focal sacral posterior dysraphism is also conspicuous. In general, lipomas are considerably more conspicuous on T1WI than T2WI.

Axial T1WI MR at the lumbosacral transition reveals that the abnormal elongated, low-lying spinal cord
continues to the sacral level.

TERMINOLOGY

Synonyms

  • Tethered cord syndrome (TCS), tight filum terminale syndrome (TFTS)

Definitions

  • Symptoms and imaging findings related to low-lying conus medullaris tethered by short, thick filum terminale

IMAGING

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