Myasthenia Gravis Symptoms
Myasthenia gravis presents with fluctuating, fatigable muscle weakness that worsens with activity and improves with rest, most characteristically affecting the eyes (ptosis and diplopia), face, throat, and limbs. 1, 2
Ocular Symptoms (Most Common Initial Presentation)
50% of patients present with ocular symptoms only, including:
- Ptosis (drooping eyelids) that worsens with prolonged upgaze and fatigue
- Diplopia (double vision) from variable extraocular muscle weakness
- Cogan lid-twitch sign - brief eyelid overshoot when looking down then up
- Slow ocular saccades
- Variable strabismus that changes throughout the day 1, 2
Critical pitfall: Of those presenting with purely ocular symptoms, 50-80% will progress to generalized myasthenia gravis within a few years 1
Bulbar Symptoms
When the disease affects throat and facial muscles:
- Dysphagia (difficulty swallowing)
- Dysarthria (slurred speech)
- Facial muscle weakness
- Difficulty chewing
- Difficulty holding up the head
- Tongue weakness (rare but reported) 1, 3
Generalized Symptoms
When myasthenia becomes generalized, it involves:
- Limb weakness - typically proximal more than distal (though atypical distal presentations occur) 1, 4
- Respiratory muscle weakness - can lead to life-threatening respiratory failure and myasthenic crisis 1, 5
- Neck muscle weakness
- Variable motor weakness affecting large motor groups 1
Pathognomonic Features
The hallmark characteristic is fluctuation and fatigability:
- Symptoms worsen with repetitive use of affected muscles
- Symptoms worsen later in the day
- Symptoms improve with rest
- Ice pack test positive - applying ice to closed eyes for 2 minutes improves ptosis by ~2mm, or 5 minutes improves strabismus 1, 2
- Symptoms vary from examination to examination 1
What Myasthenia Does NOT Typically Cause
Pupils are typically NOT affected (though rare impaired responses reported) - pupillary involvement should prompt consideration of third nerve palsy instead 1, 2
Pain is NOT a feature - weakness is painless 6
Age and Onset Patterns
- Adults: Onset typically in third to fourth decade, sometimes much later in males 1
- No geographic or racial predilection 1, 2
- Increased risk with autoimmune thyroid disease and thymoma 1
Recognition Urgency
Immediate recognition is critical because:
- Generalized disease can cause life-threatening respiratory failure 1
- Early diagnosis allows prevention of progression to myasthenic crisis 5
- All grades warrant workup given potential for respiratory compromise 5
The disease is known as "the great masquerader" because it can mimic many types of strabismus, neuropathies, and other neuromuscular conditions, making clinical suspicion essential when encountering fluctuating, fatigable weakness 1.