- Triad: Ptosis, Oculomotor paresis and Obicularis oculi weakness
- Ptosis may be unilateral or bilateral
- Alternating ptosis is specific for this condition
- Eyelid fatigue
- Ptosis worsens with prolonged upgaze or upon return to primary gaze
- Cogan's lid twitch
- After brief but sustained downgaze, a saccade to primary gaze results in the eyelid quickly rising and falling (1 mm or more typically)
- Eyelid Curtaining
- When lifting the more ptotic eyelid, the contralateral eyelid will droop more because of Hering's law
- Resting for 5 minutes with the eyes closed will cause improvement in ptosis
- Strabismus that fluctuates or appears fatiguable
- Any type of strabismus possible
- prolonged or sustained gaze in the field of action of the affected muscle may show increasing paresis
- Lagophthalmos is rare
- attempt to open the eyelid against forced closue- if the eyelid can be opened it suggest obicularis weakness
- Acetylcholine Receptor Antibody
- sensitivity 50% in Ocular myasthenia vs 90% in Generalized myasthenia
- The most specific test, no false positives have been reported
- Muscle specific tyrosine kinase antibodies (MuSK)
- Rare cares of this antibody present in the setting of ocular myathenia without acetylcholine receptor antibodies
- LRP4 antibodies
- 3 cases reported these present in setting of ocular myasthenia
- Ice Pack Test
- Place a bag of ice on the ptotic lid for 1 minute
- Immediately asses ptosis when ice removed
- improvement is transient (<1 min)
- sensitivity 80% if prominent ptosis present
- Tensilon test
- Edrophonium- inhibits acetylcholinesterase
- transiently reverses muscle weakness
- Sensitivity 85-95%
- Electrophysiology
- Repetitive nerve stimlation- reduction in amplitudes with repetitive stimulation
- Single-fiber EMG- temoral variability of adjacent motor nerve fibers known as “jitter”.
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