Differential Diagnosis for 51 Year Old Female with Right Arm and Left Leg Weakness

Single Most Likely Diagnosis

• Stroke: The most common cause of sudden onset unilateral weakness is a stroke, which can be ischemic or hemorrhagic. The pattern of weakness (right arm and left leg) suggests a lesion in the left hemisphere of the brain, possibly involving the motor cortex or the internal capsule.

Other Likely Diagnoses

• Multiple Sclerosis: An autoimmune disease that affects the central nervous system, causing demyelination and a wide range of neurological symptoms, including weakness. The pattern of weakness could be consistent with a plaque in the central nervous system affecting the motor pathways.
• Spinal Cord Lesion: A lesion in the spinal cord, such as a tumor, infection, or trauma, could cause weakness in a specific pattern depending on the level and location of the lesion.
• Peripheral Neuropathy: Although less likely to cause such a specific pattern of weakness, certain types of peripheral neuropathy (e.g., mononeuritis multiplex) could potentially cause weakness in multiple limbs.

Do Not Miss Diagnoses

• Brain Tumor: A tumor in the brain could cause focal neurological deficits, including weakness. It's crucial to consider this diagnosis due to its significant implications for treatment and prognosis.
• Subarachnoid Hemorrhage: A sudden onset of weakness could be a sign of a subarachnoid hemorrhage, especially if accompanied by other symptoms like headache or altered mental status.
• Spinal Cord Compression: Compression of the spinal cord due to any cause (e.g., metastatic cancer, abscess, hematoma) is a medical emergency that requires prompt diagnosis and treatment to prevent permanent neurological damage.

Rare Diagnoses

• Acute Demyelinating Neuropathy (Guillain-Barré Syndrome): Although typically presents with ascending paralysis, in rare cases, it could start with an asymmetric pattern of weakness.
• Neurosarcoidosis: Sarcoidosis affecting the central nervous system could cause a variety of neurological symptoms, including weakness, but it is a rare condition.
• Vasculitis (e.g., Giant Cell Arteritis, Primary Central Nervous System Vasculitis): These conditions are rare and can cause stroke-like symptoms, including weakness, due to inflammation of blood vessels.