Differential Diagnosis for Facial Weakness

The patient's symptoms of facial weakness, diplopia, difficulty opening her eyes, and progressive weakness throughout the day suggest a neuromuscular disorder. Here is a differential diagnosis organized into categories:

• Single Most Likely Diagnosis
  • Myasthenia Gravis: This autoimmune disorder is characterized by fluctuating muscle weakness that worsens with activity and improves with rest. The patient's symptoms of diplopia, difficulty opening her eyes, and progressive weakness throughout the day are classic for myasthenia gravis.
• Other Likely Diagnoses
  • Lambert-Eaton Myasthenic Syndrome (LEMS): This is another autoimmune disorder that causes muscle weakness, but it typically starts in the lower limbs and progresses to the upper body. However, some patients may present with ocular and bulbar symptoms similar to myasthenia gravis.
  • Congenital Myasthenic Syndromes: These are a group of rare genetic disorders that affect the neuromuscular junction and can cause muscle weakness, but they typically present in childhood.
  • Botulism: This is a rare but potentially life-threatening condition caused by a toxin that affects the neuromuscular junction, leading to muscle weakness, diplopia, and difficulty swallowing.
• Do Not Miss Diagnoses
  • Guillain-Barré Syndrome: This is an autoimmune disorder that can cause rapid progression of muscle weakness, which can lead to respiratory failure if not promptly treated.
  • Brainstem Stroke or Tumor: Although less likely, a brainstem stroke or tumor can cause facial weakness, diplopia, and difficulty swallowing, and would be a medical emergency.
• Rare Diagnoses
  • Mitochondrial Myopathies: These are a group of rare genetic disorders that affect the mitochondria and can cause muscle weakness, but they typically present with other systemic symptoms.
  • Inflammatory Myopathies: These are a group of rare autoimmune disorders that cause muscle inflammation and weakness, but they typically present with proximal muscle weakness rather than ocular and bulbar symptoms.