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Paraspinous muscle weakness Clinical features Weakness of trunk extension Stooped posture Neuromuscular disorders: Deformity not fixed Amyotrophic lateral sclerosis Paraspinous myopathies "Bent spine" syndrome (Camptocormia) Cervical paraspinous myopathy: Head ptosis Myasthenia Gravis Myopathies Dystrophy Limb girdle: 2B FSH DM2 Scapuloperoneal 1 Myopathies with mutations in RYR receptor Metabolic myopathy Acid maltase deficiency Carnitine deficiency Inflammatory Polymyositis Inclusion body myositis Also see: Neck weakness, posterior Motor neuron disorders Spinal muscular atrophy Benign focal amyotrophy of paraspinous muscles1 Valproate toxicity (Reversible) Spine & spinal cord disorders: Fixed deformity Ankylosing spondylitis Vertebral fracture: May be associated with osteoporosis Syringomyelia Movement & CNS disorders: Paraspinous involvement after onset of extrapyramidal syndrome Gait disorders of aging Parkinsonism Multiple system atrophy (MSA) Dystonias Psychiatric disorders Also see Posterior Neck Weakness

Vesalius

"Bent Spine" Syndrome²

• Etiology: Family history positive in up to 50%
• Onset: 4th to 7th decade; Idiopathic disorders usually > 50 years
• Epidemiology: Females > Males
• Clinical
  • Paraspinous muscles
    • Reduced strength
    • Stooped posture when erect
    • Posterior neck muscles may be involved
  • Limb muscles
    • Normal strength
    • Fatigue with repetitive movements
  • Course: Slowly progressive
  • Spinal: Upper thoracic kyphosis
• Laboratory
  • Muscle CT & MRI
    • Paraspinous muscles: Hypodensity; Fat infiltration
  • EMG
    • Paraspinous: Myopathic 75%
    • Limb: Myopathic 50%
  • Serum CK
    • Normal (75%)
    • Mildly high in minority: Up to 5x elevated
  • Muscle biopsy
    • Paraspinous muscles
      • Variable muscle fiber size
      • Endomysial fibrosis
      • Little necrosis or regeneration
      • Internal architecture: Disorganized, but same change may occur in normal paraspinous muscle
    • Limb muscles: Minor or Non-diagnostic changes
• Differential diagnosis: Other causes of paraspinous muscle weakness

Bent Spine syndrome MRI: T2 images

Wasting & Fibrosis (T-spine): Symmetric, Severe (Arrows)

Wasting & Fibrosis (L-spine): Asymmetric (Arrow)