Why is a left‑sided thoracic scoliosis curve more concerning in a 24‑year‑old woman who has left‑arm and shoulder pain with crepitus, despite being considered orthopaedic rather than cardiac?

Why Left-Sided Thoracic Scoliosis Is More Concerning

A left thoracic scoliosis curve is concerning because it is strongly associated with underlying neural axis abnormalities—including Chiari malformations, syringomyelia, tethered cord, and spinal cord tumors—that occur in up to 54% of these patients, compared to the typical right thoracic pattern seen in benign idiopathic scoliosis. 1, 2

The Atypical Pattern as a Red Flag

• Left thoracic curves are inherently atypical because adolescent idiopathic scoliosis (the most common form, accounting for 75–80% of pediatric scoliosis) typically presents with a right thoracic curve pattern. 1

• When the curve deviates to the left, it signals that the scoliosis may not be idiopathic but rather secondary to an intraspinal pathology. 1

• The American College of Radiology explicitly lists left-sided thoracic curve as one of the key risk factors that should prompt MRI evaluation of the entire spine to exclude neural axis abnormalities. 1, 3

High Prevalence of Neural Axis Abnormalities

• A prospective study of 68 patients with presumed "idiopathic" left thoracic scoliosis found that 54% had neural axis abnormalities on MRI, including:

  • Chiari I malformation (with or without syringomyelia) 2
  • Isolated syringomyelia 2
  • Tethered cord 2
  • Diastematomyelia 2
  • Arachnoid cysts 2

• These abnormalities are clinically silent in many cases—patients may have no neurologic symptoms or signs on examination—yet they pose significant risk for neurologic injury during surgical correction if undetected preoperatively. 2

• Male sex and greater curve severity further increase the likelihood of underlying pathology in left thoracic curves. 2

Why This Matters for Your Patient

• Her left arm and shoulder pain with crepitus has been attributed to orthopedic causes, which is reasonable given that musculoskeletal symptoms are common in scoliosis patients due to altered biomechanics and muscle imbalance. 4

• However, the combination of a left thoracic curve pattern and functionally disruptive pain (another ACR-listed risk factor) should raise clinical suspicion for intraspinal pathology. 1, 3

• Painful scoliosis in a young patient—especially with a left-sided curve—warrants thorough investigation to exclude serious underlying conditions such as cord syrinx, Chiari malformation, or even intrinsic spinal cord tumors. 4

Recommended Imaging Algorithm

If not already performed, obtain MRI of the entire spine without IV contrast to definitively exclude neural axis abnormalities. 1, 3

• MRI detects intraspinal anomalies in 2–4% of adolescents with idiopathic scoliosis overall, but this rate climbs to 54% in left thoracic curves. 1, 2

• The most common findings are Chiari I malformation, cord syrinx, and tethered cord—all of which can influence surgical planning and long-term management. 1

• Contrast is not routinely required unless there is clinical suspicion for tumor or infection. 3

Common Pitfalls to Avoid

• Do not rely solely on a normal neurologic examination to exclude intraspinal pathology; many neural axis abnormalities are asymptomatic until surgical manipulation or progressive cord compression occurs. 1, 2

• Do not dismiss left thoracic curves as "just idiopathic scoliosis" without MRI screening, as the high prevalence of underlying anomalies makes this pattern inherently high-risk. 1, 2

• Painful scoliosis in a child or adolescent is never normal—idiopathic scoliosis is typically painless, so pain (especially if functionally disruptive) should prompt further investigation. 4

Clinical Context: Orthopedic vs. Neurologic Pain

• While her arm and shoulder symptoms may indeed be orthopedic (related to muscle strain, postural asymmetry, or shoulder imbalance from the spinal deformity), the left thoracic curve pattern itself is the primary concern—not the arm pain per se. 1, 2

• The concern is that an undetected intraspinal lesion (such as a syrinx or Chiari malformation) could lead to neurologic deterioration over time or catastrophic injury during corrective surgery if the spine is instrumented without prior knowledge of the anomaly. 2

• Therefore, the "concerning" aspect is the curve pattern and its association with occult neural pathology, which must be ruled out before any surgical intervention is considered. 1, 2