Differential Diagnosis for Truncal Weakness

The following is a differential diagnosis for truncal weakness, categorized for clarity and emphasis on critical conditions.

• Single Most Likely Diagnosis

  • Spinal Cord Injury or Disease: This is often the most direct cause of truncal weakness due to the spinal cord's role in transmitting nerve signals from the brain to the rest of the body. Conditions affecting the spinal cord, such as injuries, tumors, or infections, can lead to weakness in the trunk and other parts of the body.

• Other Likely Diagnoses

  • Myasthenia Gravis: An autoimmune disease that affects the nerve-muscle connection, leading to weakness that can include the trunk. The weakness typically worsens with activity and improves with rest.
  • Muscular Dystrophy: A group of inherited disorders characterized by progressive muscle weakness and degeneration. Some forms can affect the trunk muscles early in the disease course.
  • Polymyositis/Dermatomyositis: Inflammatory muscle diseases that can cause progressive weakness, including in the trunk, often accompanied by skin manifestations in dermatomyositis.
  • Guillain-Barré Syndrome: An autoimmune disorder where the body's immune system mistakenly attacks part of its peripheral nervous system, leading to muscle weakness, which can start in the lower extremities and ascend to include the trunk.

• Do Not Miss Diagnoses

  • Acute Spinal Cord Compression: Requires immediate medical attention to prevent permanent damage. Causes include trauma, tumors, and abscesses.
  • Botulism: A rare but potentially life-threatening illness caused by a toxin that affects the nervous system, leading to muscle weakness, including truncal weakness.
  • Tetanus: Another toxin-mediated illness that can cause severe muscle stiffness and spasms, including in the trunk, with potentially fatal outcomes if not treated promptly.

• Rare Diagnoses

  • Mitochondrial Myopathies: A group of disorders caused by mitochondrial dysfunction, leading to muscle weakness, which can include the trunk, and other systemic symptoms.
  • Pompe Disease: A genetic disorder caused by the deficiency of acid alpha-glucosidase, leading to glycogen accumulation in muscles and potentially severe muscle weakness, including in the trunk.
  • Inclusion Body Myositis: The most common acquired myopathy in adults over 50, characterized by progressive muscle weakness and wasting, which can affect the trunk, though it more commonly affects the distal muscles.