Signs and Symptoms of Myasthenia Gravis
Myasthenia gravis is characterized by fluctuating skeletal muscle weakness that worsens with use and improves with rest, with variable presentation affecting ocular, facial, bulbar, and limb muscles. 1
Primary Clinical Manifestations
Ocular Symptoms
- Ptosis (drooping eyelids) - typically worsens with prolonged upgaze and fatigue
- Diplopia (double vision) - due to extraocular muscle weakness
- Variable strabismus (misalignment of eyes) - may change pattern with fatigue
- Slow ocular saccades (eye movements)
- Cogan lid-twitch sign - brief twitching of upper eyelid when patient shifts gaze from looking down to straight ahead
Bulbar Symptoms
- Dysarthria (slurred speech)
- Dysphagia (difficulty swallowing)
- Facial muscle weakness
- Difficulty chewing
- Difficulty holding up the head
Limb and Body Symptoms
- Fatigable muscle weakness - generally more proximal than distal
- Neck muscle weakness
- Respiratory muscle weakness - can lead to life-threatening respiratory failure
Key Diagnostic Features
Characteristic Patterns
- Weakness that worsens with repeated use of affected muscles
- Symptoms that improve with rest
- Variable presentation - symptoms may change throughout the day
- Fluctuating severity - symptoms may vary from day to day
- Absence of sensory symptoms
- Normal pupillary responses (typically) - pupillary involvement should prompt consideration of other diagnoses 2
Diagnostic Tests
- Ice pack test - application of ice over closed eyes for 2 minutes can reduce ptosis by about 2mm and reduce misalignment in myasthenia gravis 2
- Rest test - improvement of symptoms after a period of rest
Disease Classification
By Distribution
- Ocular myasthenia gravis - affects only levator, orbicularis oculi, and extraocular muscles
- Generalized myasthenia gravis - affects larger motor groups including bulbar, limb, and respiratory muscles
By Disease Course
- 50% of patients present with ocular symptoms only
- 50-80% of patients with initial ocular symptoms develop generalized myasthenia within a few years 2
High-Risk Presentations
- Respiratory involvement - requires immediate medical attention
- Bulbar symptoms - can lead to aspiration risk
- Rapidly progressive weakness - may indicate myasthenic crisis
Associated Conditions
- Thymoma - present in approximately 20% of patients 3
- Autoimmune thyroid disease - increased risk of comorbidity 2
- Other autoimmune diseases - such as Hashimoto's thyroiditis 3
Common Pitfalls in Diagnosis
- Misdiagnosis as other neurological disorders due to its variable presentation
- Failure to recognize that symptoms worsen with fatigue and improve with rest
- Missing the diagnosis in patients with isolated ocular symptoms
- Not considering myasthenia gravis as "the great masquerader" that can mimic many types of incomitant strabismus with or without ptosis 2
Warning Signs Requiring Urgent Attention
- Respiratory insufficiency - may lead to life-threatening respiratory failure
- Dysphagia - increases risk of aspiration
- Rapidly progressive symptoms - may indicate myasthenic crisis requiring ICU-level monitoring 2
Early recognition of these signs and symptoms is critical for prompt diagnosis and management, as myasthenia gravis can progress to life-threatening complications if left untreated.