30th April 2024

A 55-year-old woman presents with a 6-month history of progressive weakness in her arms and slurred speech.

A 55-year-old woman presents with a 6-month history of progressive weakness in her arms and slurred speech. She reports difficulty in holding objects and occasional choking while drinking fluids. On examination, there is evidence of muscle wasting and fasciculation in the upper limbs, brisk reflexes, and an extensor plantar response. Her sensory examination is normal.

Which investigation is most likely to confirm the diagnosis?