Clinical Manifestations of Myasthenia Gravis

Introduction to Myasthenia Gravis

• Myasthenia gravis is characterized by fluctuating and fatigable muscle weakness that worsens with repeated muscle use and improves with rest, typically affecting the ocular, bulbar, and limb muscles in variable combinations 1, 2

Ocular Manifestations

• Ptosis (eyelid drooping) that worsens with sustained upward gaze and improves with rest 1, 2
• Diplopia (double vision) caused by weakness of the extraocular muscles, typically asymmetric and variable 2
• The absence of pupillary involvement is a crucial distinctive sign that differentiates myasthenia gravis from other causes of ophthalmoplegia 1, 3

Bulbar Manifestations

• Dysarthria (slurred speech) that worsens with prolonged speech 2, 4
• Dysphagia (difficulty swallowing) - a particularly concerning sign that requires immediate evaluation 2, 4

Limb and Trunk Manifestations

• Proximal muscle weakness more than distal muscle weakness 2
• Difficulty climbing stairs, indicating weakness of the lower limbs 3
• Neck weakness that can progress 2
• Respiratory muscle weakness - can lead to potentially life-threatening respiratory failure 1, 2

Distinctive Clinical Characteristics

• Variability: symptoms fluctuate throughout the day and can present with completely different patterns with fatigue or repeated examination 1
• Positive ice test: the application of an ice pack can temporarily reduce or eliminate both extraocular motility disturbances and ptosis 1, 3

Urgent Evaluation Signs

• Any respiratory symptoms, including difficulty breathing with light activity 3, 4
• Progressive or new-onset dysphagia 2, 4
• Neck or respiratory muscle weakness 2
• Hoarseness that may indicate bulbar involvement 3

Important Considerations

• Approximately 50% of patients with myasthenia gravis present with solely ocular symptoms at onset, but most will progress to generalized disease 1, 3
• The absence of pupillary involvement is a critical distinctive sign - if pupils are abnormal, other etiologies should be carefully considered, particularly third cranial nerve palsy 1, 3