Tethered Cord Syndrome¶

Definition¶

Tethered cord syndrome (TCS) results from abnormal fixation of the spinal cord at the caudal end, restricting its normal ascent during growth and placing traction on the conus medullaris. The normal conus position is at or above the L1–L2 disc level in adults and L2–L3 in neonates. A conus below L2–L3 in neonates or below L2 in adults, combined with a thickened filum terminale (>2 mm), suggests tethering. The diagnosis of tethered cord syndrome requires correlation of imaging findings with clinical symptoms — progressive lower extremity weakness, foot deformities, scoliosis, and/or bladder dysfunction.

Causes¶

Tight filum terminale — Thickened, fibrofatty filum (most common cause of occult tethered cord)
Lipomyelomeningocele — Lipoma tethering the cord
Post-surgical — Scar tissue after myelomeningocele repair
Diastematomyelia — Bony or fibrous septum tethering one or both hemicords
Dermal sinus tract — Tract extending from skin to cord
Lipoma of the filum terminale — Fatty infiltration of the filum

Imaging Findings¶

MRI (Modality of Choice)¶

Low-lying conus — Conus tip below L2–L3 in neonates or below L2 in adults
Thickened filum terminale — >2 mm on axial images, often with fatty signal (bright on T1)
Dorsal positioning of the cord — The tethered cord lies against the posterior wall of the thecal sac rather than floating centrally
Associated anomalies — Lipoma, diastematomyelia, dermal sinus, syringomyelia
Fat-saturated sequences — Confirm fatty filum by showing signal dropout

Ultrasound (Neonates)¶

Useful screening tool before posterior element ossification (up to 3–6 months)
Low conus position and thickened filum can be identified
Limited by ossification in older children

Clinical Pearl

A fatty filum terminale (bright on T1, >2 mm) with a borderline-low conus is a common incidental finding on lumbar MRI. Not all fatty fila cause symptoms. The diagnosis of tethered cord syndrome requires correlation of imaging findings with clinical symptoms — progressive lower extremity weakness, foot deformities, scoliosis, and/or bladder dysfunction. Asymptomatic fatty fila in adults are generally observed.

Key Points¶

Conus below L2 (adults) or L2–L3 (neonates) with thickened filum suggests tethering
MRI is the modality of choice — evaluate conus level, filum thickness, and associated anomalies
Fatty filum (bright T1, >2 mm) is the most common cause of occult tethered cord
Clinical correlation is essential — not all low-lying coni are symptomatic
Surgical untethering is indicated for symptomatic patients to prevent progressive neurological deterioration

References¶

Weisbrod LJ, Thorell W. Tethered Cord Syndrome (TCS). In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2023. https://www.ncbi.nlm.nih.gov/books/NBK585121/
Otto N, Kucera J, Hayes LL, Chandra T. Tethered Cord Syndrome: Role of Imaging Findings in Surgical Decision-Making. Cureus. 2023;15(9):e44854. doi:10.7759/cureus.44854. PMID: 37809232; PMCID: PMC10560071.
Hertzler DA 2nd, DePowell JJ, Stevenson CB, Mangano FT. Tethered cord syndrome: a review of the literature from embryology to adult presentation. Neurosurg Focus. 2010;29(1):E1. doi:10.3171/2010.3.FOCUS1079. PMID: 20593997.
Raghavan N, Barkovich AJ, Edwards M, Norman D. MR imaging in the tethered spinal cord syndrome. AJR Am J Roentgenol. 1989;152(4):843-52. PMID: 2784267.
Singh S, Kline-Fath B, Bierbrauer K, Racadio JM, Salisbury S, Macaluso M, Jackson EC, Egelhoff JC. Comparison of standard, prone and cine MRI in the evaluation of tethered cord. Pediatr Radiol. 2012;42(6):685-91. doi:10.1007/s00247-011-2308-8. PMID: 22143965.
Gaillard F, et al. Tethered cord syndrome. Radiopaedia.org. Available from: https://radiopaedia.org/articles/tethered-cord-syndrome-2