Symptoms of Myasthenia Gravis
Myasthenia gravis presents with fatigable or fluctuating muscle weakness that characteristically worsens with continued use and improves with rest, most commonly affecting ocular, bulbar, and respiratory muscles in a proximal-to-distal pattern. 1
Ocular Manifestations (Most Common Initial Presentation)
- Ptosis (drooping eyelids) is often the first symptom, appearing unilaterally or bilaterally and worsening with prolonged upgaze 1, 2
- Diplopia (double vision) results from extraocular muscle weakness and abnormal eye movements 1, 2
- Variable strabismus (eye misalignment) that changes throughout the day or with fatigue 1
- Slow ocular saccades are characteristic 1
- Cogan lid-twitch sign may be present on examination 1
- 50% of patients initially present with purely ocular symptoms, and 50-80% of these will progress to generalized disease within a few years 1, 2
Bulbar Symptoms
- Dysarthria (slurred speech) from facial and oropharyngeal muscle weakness 1, 2
- Dysphagia (difficulty swallowing) affecting eating and drinking 1, 2
- Facial muscle weakness causing reduced facial expressions 1, 2
- Difficulty chewing that worsens during meals 1
Limb and Axial Muscle Involvement
- Proximal muscle weakness affecting shoulders and hips more than hands and feet 1, 2
- Neck weakness causing difficulty holding up the head 1, 2
- Difficulty climbing stairs from proximal leg weakness 1
- Variable motor weakness that fluctuates throughout the day 1
Respiratory Manifestations (Most Serious)
- Respiratory muscle weakness that can progress to respiratory insufficiency 1, 2
- Dyspnea (shortness of breath) particularly with exertion 1
- Potential for myasthenic crisis with life-threatening respiratory failure requiring intensive care 1, 2
Characteristic Clinical Features
- Fluctuating weakness is the hallmark—symptoms vary throughout the day and from day to day 1, 2
- Fatigability with worsening symptoms as the day progresses or with repetitive activity 1, 2
- Improvement with rest or application of ice (ice pack test positive) 1
- Variable examination findings that change during prolonged testing 1
- Pupils typically unaffected, though rare cases may show impaired responses 1
Important Clinical Pitfalls
Avoid missing respiratory compromise, as myasthenia gravis can rapidly progress to life-threatening myasthenic crisis requiring mechanical ventilation 1, 2. All grades warrant evaluation given this potential for respiratory decompensation 1.
Be aware that certain medications worsen myasthenia symptoms: β-blockers, IV magnesium, fluoroquinolones, aminoglycosides, and macrolide antibiotics should be avoided 1, 2.
Pupillary involvement should prompt consideration of alternative diagnoses such as third nerve palsy rather than myasthenia gravis 1.