Differential Diagnosis for Right Arm Weakness and No Sensation

• Single most likely diagnosis
  • Stroke (ischemic or hemorrhagic): This is the most likely diagnosis due to the sudden onset of unilateral weakness and sensory loss, which are classic symptoms of a stroke. The lack of sensation in the right arm further supports this diagnosis, as strokes often affect both motor and sensory pathways.
• Other Likely diagnoses
  • Brachial plexus injury: Trauma to the brachial plexus can cause weakness and sensory loss in the arm, depending on which nerves are damaged. This could be due to a fall, accident, or other forms of physical trauma.
  • Radiculopathy (C5-C6 or C7 nerve root compression): Compression of the nerve roots in the cervical spine can lead to weakness and sensory loss in the arm. This is often due to a herniated disc, osteophyte, or other compressive lesion.
  • Peripheral neuropathy (mononeuropathy): Although less common, a mononeuropathy affecting the nerves of the arm could result in weakness and sensory loss. This could be due to various causes such as diabetes, trauma, or compression.
• Do Not Miss diagnoses
  • Spinal cord injury or compression: Conditions like spinal cord compression due to a tumor, abscess, or hematoma can present with sudden onset of weakness and sensory loss. Missing this diagnosis could lead to permanent neurological damage if not promptly treated.
  • Multiple sclerosis: Although less likely, multiple sclerosis (MS) can present with a wide range of neurological symptoms, including weakness and sensory loss in one arm. MS is a condition that affects the central nervous system and can have a highly variable presentation.
  • Vasculitis (e.g., giant cell arteritis, primary CNS vasculitis): Vasculitis affecting the blood vessels supplying the brain or spinal cord can lead to stroke-like symptoms, including unilateral weakness and sensory loss. These conditions require prompt diagnosis and treatment to prevent further complications.
• Rare diagnoses
  • Amyotrophic lateral sclerosis (ALS): A progressive neurological disease that affects nerve cells in the brain and spinal cord, leading to loss of muscle control. ALS can present with unilateral weakness, but the absence of sensation makes this a less likely diagnosis.
  • Syringomyelia: A disorder in which a fluid-filled cavity forms within the spinal cord, leading to sensory loss and weakness. This condition is rare and typically presents with a "dissociated sensory loss" (loss of pain and temperature sensation with preservation of light touch and proprioception).
  • Neoplastic lesions (e.g., schwannoma, neurofibroma): Tumors arising from the nerves can cause localized weakness and sensory loss, depending on their location and the nerves they compress. These are rare causes of the presenting symptoms.