What is the best imaging study to diagnose a tethered spinal cord (TSC) in a 10-year-old child with urinary incontinence?

MRI Without Contrast is the Best Imaging for Tethered Spinal Cord in a Child with Urinary Incontinence

MRI of the lumbar spine without IV contrast is the imaging modality of choice for diagnosing tethered spinal cord syndrome in a 10-year-old child presenting with urinary incontinence. 1

Rationale for MRI as First-Line Imaging

MRI offers several advantages for diagnosing tethered cord syndrome (TCS):

• Superior soft-tissue contrast for visualizing the spinal cord, nerve roots, and surrounding structures
• Ability to accurately assess the position of the conus medullaris
• Detection of associated anomalies such as fatty filum terminale, lipomas, or dermal sinuses
• No radiation exposure, which is particularly important in pediatric patients
• Capability to identify occult forms of tethered cord that may be missed on other imaging modalities 1

Clinical Correlation with Urinary Symptoms

Urinary incontinence is a classic presenting symptom of tethered cord syndrome in children. The American College of Radiology guidelines highlight that urologic dysfunction is an important presenting feature of spinal cord tethering 1. Once a child is toilet trained, the onset of secondary urinary incontinence is the most common presentation of a tethering lesion, often accompanied by:

• Urgency
• Urge incontinence
• Sudden or stress incontinence
• New-onset enuresis
• Urinary frequency
• Nocturia 1

Diagnostic Algorithm for Suspected Tethered Cord

1. Initial Assessment: Evaluate for associated signs and symptoms:

   • Urologic symptoms (incontinence, frequency, UTIs)
   • Orthopedic abnormalities (scoliosis, foot deformities)
   • Neurological deficits (sensory/motor loss in lower extremities)
   • Cutaneous markers (dimples, hairy patches, hemangiomas)

2. First-Line Imaging: MRI lumbar spine without IV contrast

   • Allows visualization of the conus medullaris position (normally at L1-L2)
   • Can identify fatty filum terminale, lipomas, or other causes of tethering
   • Provides detailed assessment of associated spinal anomalies

3. Secondary Imaging (only if MRI is contraindicated or unavailable):

   • CT myelography may be considered but is invasive and involves radiation

Evidence Supporting MRI

Multiple studies confirm MRI's superiority for diagnosing tethered cord syndrome:

• A case report of a 10-year-old boy with bladder and anal incontinence demonstrated that lumbosacral MRI was definitive in confirming tethered cord syndrome 2

• In a study of 18 children with daytime urinary incontinence, spinal MRI was used to diagnose various forms of tethered cord syndrome including filum lipoma, occult tethered cord syndrome, low-set conus, conus lipoma, and sacral meningeal cyst 3

• Early diagnosis with MRI and subsequent neurosurgical treatment may prevent progression of urinary incontinence 4

Common Findings on MRI

MRI may reveal:

• Low-lying conus medullaris (below L2 level)
• Thickened or fatty filum terminale
• Lipomas
• Dermal sinuses
• Diastematomyelia (split cord)
• Syringomyelia

Clinical Pitfalls to Avoid

1. Delayed Diagnosis: Failure to consider tethered cord in a child with new-onset urinary symptoms can lead to irreversible neurological damage. Early diagnosis and treatment are essential for better outcomes 4.

2. Missing Occult Forms: Some patients have occult tethered cord syndrome with normal-appearing MRI but functional tethering. In these cases, urodynamic studies and neurophysiological testing may be necessary to confirm the diagnosis 5.

3. Overlooking Associated Conditions: Up to 75% of patients with spinal dysraphism present with lower extremity neurological and orthopedic abnormalities that should be evaluated concurrently 1.

4. Inadequate Follow-up: Even after surgical untethering, patients require long-term follow-up as retethering can occur. Post-operative MRI serves as a baseline for future comparison 6.

In summary, MRI without contrast is the definitive imaging study for evaluating tethered cord syndrome in a child with urinary incontinence, offering superior visualization of neural structures without radiation exposure.