What Causes Levoscoliosis
Levoscoliosis (left-sided spinal curvature) has multiple potential causes including idiopathic factors (most common), congenital vertebral anomalies, neuromuscular disorders, and underlying neural axis abnormalities—with left-sided curves being particularly concerning as they represent an atypical pattern that warrants investigation for spinal cord pathology. 1, 2
Primary Etiologic Categories
Idiopathic Causes (Most Common)
- Adolescent idiopathic scoliosis accounts for 75-80% of all scoliosis cases, though left thoracic or thoracolumbar curves are much less common than the typical right thoracic pattern 2
- The underlying mechanisms likely involve alterations in skeletal growth, neuromuscular imbalances, and disturbances in brain-spine communication 3
- Genetic and environmental factors contribute to occurrence, with both phenotypic and genetic heterogeneity complicating understanding of the genetic basis 3
Congenital Causes
- Congenital scoliosis results from morphogenic abnormalities in vertebral development, including vertebral segmentation anomalies and structural malformations 1, 3
- These developmental defects occur during embryonic formation of the spine 4
Neuromuscular Causes
- Central nervous system disorders such as cerebral palsy and spinal cord injury commonly produce scoliosis 5
- Motor neuron disorders including spinal muscular atrophy 5
- Muscle fiber disorders such as Duchenne muscular dystrophy 5
- Multifactorial conditions like spina bifida 5
- Contributing factors include asymmetric paraplegia, imbalance of mechanical forces, altered sensory feedback, and abnormal posture via central pathways 5, 6
Critical Distinction: Left-Sided Curves as Red Flags
Neural Axis Abnormalities
- Left thoracic or thoracolumbar curves should prompt immediate investigation for underlying neural axis pathology 2
- MRI studies reveal that 2-4% of patients diagnosed with idiopathic scoliosis actually have neural axis abnormalities causing their scoliosis 2
- Specific pathologies include:
Additional Risk Factors Requiring Investigation
When levoscoliosis is present, evaluate for these concerning features that increase likelihood of underlying pathology 2:
- Short segment curve
- Absence of apical segment lordosis/kyphosis
- Long thoracolumbar curve
- Rapid curve progression
- Functionally disruptive pain
- Focal neurologic findings
- Male sex
- Pes cavus
Diagnostic Approach
The diagnosis of idiopathic levoscoliosis is one of exclusion, requiring absence of neuromuscular disorders, intramedullary or extramedullary abnormalities, vertebral abnormalities, and conditions with dysplastic skeletal development 2
MRI of the entire spine is warranted when left-sided curves are identified to rule out underlying pathology before attributing the deformity to idiopathic causes 2
Clinical Pitfall to Avoid
The most critical error is assuming a left-sided curve is idiopathic without neuroimaging evaluation. Neural axis abnormalities occur in more than 20% of patients with severe curves, and failure to identify these can lead to inappropriate treatment planning and missed opportunities for addressing the underlying cause 7