What is the etiology of back spasm?

Etiology of Back Spasm

Back spasms are primarily caused by muscle strain, spondylolysis/spondylolisthesis, and disc herniation, with muscle strain being the most common benign etiology in both adults and children. 1

Primary Etiological Factors

Mechanical Causes

• Muscle strain: Most common cause, typically from:
  • Overexertion during physical activity
  • Poor posture
  • Improper lifting techniques
  • Sudden movements
• Structural abnormalities:
  • Spondylolysis/spondylolisthesis (especially in pediatric populations)
  • Disc herniation causing nerve root irritation
  • Spinal stenosis

Inflammatory and Infectious Causes

• Vertebral body osteomyelitis and discitis: More common in children between 2-12 years 1
  • Clinical presentation: persistent nighttime pain, low-grade fever, decreased range of motion, irritability, localized tenderness, limping
  • Laboratory findings: leukocytosis, elevated ESR and CRP
• Inflammatory arthropathies:
  • Juvenile idiopathic arthritis in children (commonly affecting cervical spine)
  • Spondyloarthropathies with enthesitis

Neoplastic Causes

• Spinal neoplasms: Rare but serious cause of back spasm 1
  • Presenting with persistent nighttime pain refractory to conservative management
  • May progress to motor/gait disturbances and neurological symptoms
  • Types include:
    • Benign tumors: osteochondroma, osteoblastoma, osteoid osteoma
    • Malignant tumors: leukemia, lymphoma, metastasis

Pathophysiological Mechanisms

Pain-Spasm-Pain Cycle

The evidence supports the existence of a pain-spasm-pain cycle in back disorders 2:

1. Initial pain (from any cause) triggers muscle spasm
2. Muscle spasm causes additional pain
3. This additional pain further increases muscle spasm
4. The cycle perpetuates itself

This is supported by:

• EMG studies showing increased muscular activity in patients with acute back pain
• Experimental evidence demonstrating that pain can cause muscle spasm and that muscular activity can be painful
• Clinical observations that analgesics can reduce muscle spasm, and muscle relaxant techniques can reduce pain

Altered Muscle Activity Patterns

• Patients with chronic back pain show:
  • Increased muscle activity in static postures
  • Reduced muscle activity during movement 2
  • Higher levels of low back muscle activity during contraction of other muscle groups (co-contraction) 3

Clinical Implications

Assessment for Serious Underlying Pathology

Look for red flags that may indicate serious underlying causes:

• History of cancer
• Unexplained weight loss
• Fever or signs of infection
• Immunosuppression
• IV drug use
• Pain lasting >4 weeks despite conservative treatment 4

Neurological Red Flags

• Progressive neurological deficits
• Cauda equina syndrome symptoms (urinary retention, saddle anesthesia)
• Motor weakness greater than grade 3
• Severe or worsening radicular pain 4

Treatment Considerations

• For muscle spasm associated with acute low back pain:
  • Combination therapy with NSAIDs and muscle relaxants has shown better efficacy than NSAIDs alone 5
  • Muscle relaxants like cyclobenzaprine can effectively reduce objective muscle spasm and improve range of motion 5
  • Thiocolchicoside has shown efficacy with fewer sedative effects compared to other muscle relaxants 6

Caveat

Back spasm is often a symptom rather than a primary diagnosis. Identifying and addressing the underlying cause is crucial for effective management and preventing recurrence. In children especially, it's imperative to exclude serious diagnoses such as infection, neoplasm, and inflammatory diseases through appropriate imaging and laboratory testing 1.