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SYMPTOMS
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Diplopia, Droopy eyelids, and Blurry vision especially towards the end of the day
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SIGNS
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Signs are typically noted when there is muscle fatigue, especially toward the end of the day. Signs also tend to be asymmetric.
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Drooping eyelids (first sign in 50% of cases), Enhanced ptosis (When pulling up the more ptotic eyelid, the other eyelid will then have the more ptotic lid), Cogan’s sign, Eyelid twitching, Difficulty looking up, Difficulty with adduction, Slow velocity saccades, Orbicularis oculi muscle weakness (Eyelids are easily opened)
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Pupils are typically normal
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WORK-UP
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Pupils | EOMs | Cover test | Complete eye exam with dilation | Cranial nerve testing | Ptosis testing
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Sustained upgaze fatigued test: Have patient look up for 2 minutes and should notice a worsening of the ptosis Ice pack test: Place ice on eye with ptosis for 2 minutes and should notice an improvement in the ptosis. If ice pack is left on the eye with ocular motility issues for 5 minutes, there should be an improvement with ocular motility
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Rest test: Improvement in ptosis after eyes have been closed for about 20 minutes
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TREATMENT
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May need to patch one eye in order to help with diplopia
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May need to use tape or glasses with crutches to keep the eyelids elevated
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Refer to neuro-ophthalmology/neurology for further evaluation and treatment
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FOLLOW-UP
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Patient will likely be followed up by neurology/neuro-ophthalmology on a regular basis. Patient should be evaluated once myasthenia gravis is treated and stable
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ADDITIONAL LAB | TESTS
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Tensilon test | Acetylcholine receptor antibody assay | Single fiber Electromyography | Chest CT to look for a thymoma | Thyroid panel | MRI of the brain with and without contrast
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ETIOLOGY
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Autoimmune disease where anti-acetylcholine receptor antibodies at the neuromuscular junction prevent transmission of nerve signals to the muscle
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DIFFERENTIAL DX
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Cranial nerve III palsy, Cranial nerve IV palsy, Cranial nerve VI palsy, Internuclear ophthalmoplegia
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NOTES
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About 85% of patients will only have ocular signs of myasthenia gravis and usually develop systemic signs within 2 years
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Systemic signs include dysphagia, dyspnea, dysphonia, and muscle weakness
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Certain medications can exacerbate the ocular signs of myasthenia gravis and should be avoided. They include: · Aminoglycosides · Fluoroquinolones · Azithromycin · Beta blockers · Quinine
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