Differential Diagnosis for Right Arm Weakness

The following is a differential diagnosis for right arm weakness, categorized for clarity and emphasis on potential severity.

• Single Most Likely Diagnosis

  • Stroke: The most common cause of sudden arm weakness, particularly if it is unilateral and accompanied by other symptoms such as facial weakness, speech difficulties, or sensory changes. The high prevalence and potential for severe outcomes make it a primary consideration.

• Other Likely Diagnoses

  • Radial Neuropathy: Compression or injury to the radial nerve can cause weakness, particularly in the extensor muscles of the wrist and fingers, leading to difficulties with extension.
  • Cervical Spondylosis or Disc Herniation: Compression of the spinal cord or nerve roots in the cervical spine can lead to arm weakness, often accompanied by neck pain and possibly sensory changes.
  • Brachial Plexus Injury: Trauma to the brachial plexus, a network of nerves that conducts signals from the spinal cord to the shoulder and arm, can result in arm weakness, pain, and sensory deficits.

• Do Not Miss Diagnoses

  • Spinal Cord Compression: Conditions such as tumors, abscesses, or severe disc herniations can compress the spinal cord, leading to progressive weakness, sensory loss, and potentially bladder and bowel dysfunction. Early diagnosis is crucial to prevent permanent damage.
  • Multiple Sclerosis: An autoimmune disease that affects the brain and spinal cord, leading to a wide range of neurological symptoms, including arm weakness. The unpredictable nature and potential for significant disability make it a critical diagnosis not to miss.
  • 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 a diagnosis that significantly impacts prognosis and management.

• Rare Diagnoses

  • Plexiform Neurofibromas: Associated with Neurofibromatosis Type 1, these are rare tumors of the nerve sheath that can cause progressive weakness and deformity.
  • Arteriovenous Malformations (AVMs): Abnormal connections between arteries and veins, which can occur in the brain or spinal cord, potentially leading to neurological deficits, including arm weakness, due to ischemia or hemorrhage.
  • Inflammatory Myopathies: Such as polymyositis or dermatomyositis, which are autoimmune conditions that cause muscle inflammation and weakness, though they more commonly present with bilateral and proximal muscle involvement.