rhabdomyolysis

Rhabdomyolysis describes the breakdown of striated muscles with the release of intracellular contents and represents a severe muscle injury. MRI is the imaging modality of choice. Rhabdomyolysis is potentially life-threatening although recovery is excellent with early treatment.

Clinical presentation

Symptoms and signs are varied, but a classic triad of muscle pain, weakness, and dark urine are described.

Pathology

Etiology

Most common causes reported in Western adult populations is trauma/crush injury, exercise, cocaine and immobilization. The range of causes is wide:

• non-traumatic
  • infection, e.g. infectious myositis
  • electrolyte abnormalities, e.g. hypokalemia, hypocalcemia
  • immune-mediate, e.g. dermatomyositis, polymyositis
  • drugs, e.g. alcohol, cocaine, statins, anesthetic agents, heparin
  • hyperthermia/hypothermia
  • metabolic disease, e.g. myophosphorylase deficiency
  • ischemia
  • immobilization
• traumatic
  • crush injury
  • electrocution
  • excessive muscle activity, e.g. overexercise, severe forms of delayed onset muscle soreness (DOMS)

Markers

• serum creatinine kinase (CK) will be markedly raised (at least five times normal)
• elevated serum potassium
• positive urine myoglobin

Radiographic features

CT

Rhabdomyolysis has a heterogeneously hypodense appearance on CT. There may be rim-enhancement on post-contrast images .

MRI

Edema throughout affected muscles with signal intensity reflecting the severity of an injury is seen in mild-moderate cases. When severe, features of myonecrosis will be demonstrated. Two types of MRI findings have been described :

• type 1
  • T1: homogeneously iso to hyperintense
  • T2/STIR: homogeneously hyperintense
  • T1 C+ (Gd): homogeneously enhancing
• type 2
  • T1: homogeneously/heterogeneously hyperintense
  • T2: heterogeneously hyperintense
  • T1 C+ (Gd): rim-enhancing

Treatment and prognosis

The release of intracellular contents (e.g. myoglobin) can result in the development of cardiac arrhythmias, acute renal failure (~30%) and tetanus. Muscle edema may lead to compartment syndrome. Full recovery with early treatment.

Differential diagnosis

For MRI appearances consider:

• differential diagnosis of skeletal muscle edema on MRI

Siehe auch:

• infektiöse Myositis