Differential Diagnosis for Right Upper Limb Weakness

• Single most likely diagnosis
  • Stroke: This is the most common cause of sudden onset unilateral weakness, including right upper limb weakness. The justification for this diagnosis is based on the high prevalence of stroke in the population and its typical presentation with sudden focal neurological deficits.
• Other Likely diagnoses
  • Peripheral neuropathy: Conditions such as radial or median neuropathy can cause weakness in the upper limb, depending on the nerve affected. This diagnosis is considered due to the variety of neuropathies that can present with limb weakness.
  • Musculoskeletal disorders: Conditions like rotator cuff injuries or other shoulder pathologies can cause weakness in the right upper limb. These are considered because they are common and can mimic neurological weakness.
  • Spinal cord lesions: Lesions at the cervical level can cause upper limb weakness. This is a plausible diagnosis given the spinal cord's role in transmitting motor signals to the limbs.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Acute spinal cord compression: This is a medical emergency that requires immediate intervention to prevent permanent neurological damage. It's crucial to consider this diagnosis due to its severe consequences if missed.
  • Multiple sclerosis: Although less common, multiple sclerosis can present with limb weakness and is important not to miss due to its implications for long-term management and treatment.
  • Tumors (brain or spinal cord): Both primary and metastatic tumors can cause focal neurological deficits, including limb weakness. Missing this diagnosis could lead to delayed treatment of a potentially life-threatening condition.
• Rare diagnoses
  • Amyotrophic lateral sclerosis (ALS): A progressive neurological disease that affects nerve cells in the brain and spinal cord, causing loss of muscle control. ALS is rare but should be considered in the differential diagnosis of limb weakness.
  • Guillain-Barré Syndrome: An autoimmune disorder that can cause rapid-onset muscle weakness. It's rare but important to recognize due to its need for specific treatment.
  • Mitochondrial myopathies: A group of disorders caused by mitochondrial dysfunction that can lead to muscle weakness. These are rare and often have a gradual onset, but they should be considered in the differential diagnosis of unexplained limb weakness.