Differential Diagnosis for Limited Motion of the Right Hand

• Single most likely diagnosis
  • Acute Dystonic Reaction: This condition is characterized by involuntary muscle contractions, often caused by medication such as cyclobenzaprine. The patient's recent initiation of cyclobenzaprine and presentation with a clenched hand position support this diagnosis.
• Other Likely diagnoses
  • Peripheral Nerve Injury: Given the patient's history of a right shoulder injury, a peripheral nerve injury (e.g., radial or median nerve) could be causing the limited motion of the hand.
  • Muscle Spasm: The patient is already taking cyclobenzaprine, which suggests that muscle spasm is a consideration. The medication may not be effective, or the spasm could be worsening.
  • Compartment Syndrome: Although less likely without a clear injury, compartment syndrome could cause limited motion and pain in the hand.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Stroke or Transient Ischemic Attack (TIA): Although the patient's presentation is atypical, a stroke or TIA could cause sudden onset of limited motion and should be considered, especially if there are other neurological deficits.
  • Infection (e.g., Abscess or Cellulitis): Infections can cause severe pain, swelling, and limited motion, and prompt treatment is essential to prevent serious complications.
• Rare diagnoses
  • Tetanus: This rare condition can cause muscle stiffness and rigidity, but it is unlikely without a clear exposure history (e.g., wound or travel to an endemic area).
  • Hysterical Conversion Disorder: This condition involves a psychological component causing physical symptoms, including limited motion. However, this diagnosis should only be considered after ruling out other organic causes.