A 56-year-old woman with slurred speech and ptosis is showing symptoms that worsen throughout the day. What is most likely her condition?

The symptoms described in the scenario—slurred speech and ptosis (drooping of one or both eyelids)—that worsen throughout the day are characteristic of myasthenia gravis. This condition is an autoimmune disorder where antibodies develop against acetylcholine receptors at the neuromuscular junction. The hallmark of myasthenia gravis is muscle weakness that typically worsens with activity and improves with rest, resulting in fluctuating symptoms throughout the day.

In myasthenia gravis, the fatigue and weakness can lead to ocular symptoms such as ptosis and diplopia, as well as bulbar symptoms which might include slurred speech. These symptoms often fluctuate in severity, marking them distinctly from other neurological conditions.

In contrast, other conditions such as multiple sclerosis, Guillain-Barré syndrome, and ALS present differently. Multiple sclerosis has a variety of neurological symptoms related to demyelination and does not typically present with the specific pattern of worsening weakness throughout the day. Guillain-Barré syndrome often presents more acutely with ascending muscle weakness and does not exhibit the same type of fatigue pattern seen in myasthenia gravis. ALS typically presents with progressive muscle weakness but does not feature the characteristic improvement with rest and fluctuating symptoms