Yes, MRI is indicated in this case
Given the combination of a left-sided (sinistroconvex) lumbar curve and recurrent enuresis in a 15-year-old boy, spinal MRI should be performed to exclude underlying neural axis abnormalities that could be causing both conditions.
Clinical Reasoning
Key Red Flags Present
This patient presents with two significant risk factors that warrant MRI evaluation:
Left-sided thoracolumbar curve: The ACR Appropriateness Criteria explicitly identify left thoracic curves and long thoracolumbar curves as risk factors for neural axis abnormalities 1. Left-sided curves are atypical for adolescent idiopathic scoliosis and occur in only 6-7% of true AIS cases but are present in 21-38% of patients with underlying intraspinal pathology 2.
Recurrent enuresis with previous response to desmopressin: While the enuresis initially responded to treatment, its recurrence raises concern for an underlying neurological cause. Enuresis can be a subtle neurological sign, particularly when associated with spinal cord pathology such as tethered cord, syringomyelia, or Chiari malformation 1.
What MRI May Reveal
Neural axis abnormalities occur in 2-4% of adolescent scoliosis patients overall, but this rate increases substantially with risk factors 1. The most common findings include:
- Chiari I malformation (most common, accounting for ~65% of abnormalities) 3
- Syringomyelia (often associated with Chiari malformation)
- Tethered cord (which can present with enuresis)
- Diastematomyelia
Clinical Impact
While not all detected abnormalities require intervention, approximately 2% of presumed AIS patients require neurosurgical treatment before spinal fusion 4, 2. Importantly, tethered cord—which can cause enuresis—is one of the treatable conditions that may be identified 1, 3.
The combination of left lumbar curve and neurological symptoms (enuresis) increases the pretest probability of finding clinically significant pathology. Studies show that left thoracic apex curves have 37.5% sensitivity and 92.7% specificity for predicting need for neurosurgical intervention 2.
Practical Approach
MRI Protocol
- Complete spine MRI without IV contrast is the appropriate initial study 1
- Contrast is not routinely needed unless tumor or infection is suspected 5
- Imaging should extend from posterior cranial fossa to sacrum to evaluate for Chiari malformation and tethered cord 6
Common Pitfalls to Avoid
Don't dismiss the enuresis as purely functional: While monosymptomatic enuresis is common and often responds to desmopressin 7, recurrence in the context of scoliosis warrants investigation for organic causes.
Don't assume this is typical AIS: The left-sided lumbar curve pattern is atypical. True idiopathic scoliosis is a diagnosis of exclusion 1.
Don't wait for overt neurological deficits: Subtle signs like enuresis may be the only clinical indicator of significant intraspinal pathology 2.
What Happens After MRI
- If normal: Proceed with standard scoliosis management based on curve magnitude (35° may warrant bracing or observation depending on skeletal maturity)
- If abnormal: Neurosurgical consultation is mandatory before any orthopedic intervention 4, 2
- Some intraspinal abnormalities (particularly Chiari with syrinx) may require decompression before scoliosis correction to prevent neurological deterioration 1
Bottom Line
The presence of both a left lumbar curve and recurrent enuresis creates sufficient clinical suspicion to justify MRI screening. This is not routine imaging for typical AIS but rather targeted evaluation based on established risk factors. The potential to identify treatable causes of the enuresis (such as tethered cord) and to prevent surgical complications makes this a clinically prudent decision that prioritizes patient safety and optimal outcomes.