myofascial pain

Introduction

A large group of muscle disorders characterized by the presence of hypersensitive points, called trigger points.

Etiology

• trauma
• risk factors: sedentary lifestyle
  • myofascial pain syndrome
• other contributing, postulated factors
  • abnormal stresses on muscles from
    • sudden stress on shortened muscles
    • leg-length discrepancies
    • skeletal asymmetry
  • poor posture
  • static position for a prolonged period of time
  • anemia
  • hypokalemia
  • hypocalcemia
  • nutritional deficiencies
    • iron deficiency
    • vitamin C deficiency
    • thiamine deficiency
    • vitamin B6 deficiency
    • vitamin B12 deficiency
  • chronic infection
  • sleep deprivation
  • radiculopathy
  • depression
  • hypothyroidism
  • hyperuricemia
  • hypoglycemia

Epidemiology

• common
• no racial or sexual bias
• can be found in persons of all ages, even infants
• incidence increases with age into middle age

Pathology

• trigger points, within one or more muscles &/or the investing connective tissue associated with signs/symptoms

Clinical manifestations

• pain
  • local or referred pain
  • dull, aching or burning pain
  • pain may be exacerbated by
    • physical activity
    • pressure on involved tissue
    • cold exposure
    • psychosocial stress
    • infection
  • pain may be alleviated by
    • mild exercise
    • gentle stretching
    • massage
    • moist heat
    • brief rest after activity
• muscle spasm
• muscle tenderness, muscle stiffness
  • one finger points of tenderness
  • tensing of muscle may increase tenderness
• limited range of motion
• muscle weakness without atrophy
• occasionally autonomic dysfunction
• popping & clicking
• local twitch response (LTR) in the affected muscle
• trigger points, over 70% correspond to acupuncture points
• nerve entrapment may cause paresthesia, numbness

Laboratory

• no specific laboratory tests essential, but some listed below may be helpful
• complete blood count for anemia
• erythrocyte sedimentation rate (ESR)
• serum chemistry profile
  • serum K+ for hypokalemia
  • serum Ca+2, serum albumin for hypocalcemia
  • serum uric acid for hyperuricemia
  • serum glucose for hypoglycemia
• iron studies for iron deficiency
• ascorbate in blood for vitamin C deficiency
• serum thiamine for thiamine deficiency
• serum vitamin B6 for vitamin B6 deficiency
• serum vitamin B12 for vitamin B12 deficiency
• serum folate for folate deficiency
• serum TSH for hypothyroidism

Diagnostic procedures

• electromyography
  • spontaneous electrical activity over trigger points
  • lowered skin resistance to electrical current over trigger points compared to surrounding tissue

Radiology

• imaging studies are useful only to rule out other sources of pain

Complications

• not fatal condition
• significant reduction in quality of life
• major cause of time lost from work

Differential diagnosis

• neuropathic pain

Management

• physical therapy, occupational therapy
• trigger point injections
• acupuncture may be helpful
• osteopathic manipulation may be helpful
• pharmaceutical agents
  • NSAIDs
  • muscle relaxants
  • tricyclic antidepressant
  • opiates if other agents & treatment modalities not effective

More general terms

• musculoskeletal pain

More specific terms

• myofascial pain dysfunction (MPD) syndrome
• myofascial pain syndrome
• trigeminal neuralgia (tic douloureux)