Patients complain loudly about this common symptom of MG that's commonly dismissed—are docs listening?
Key Takeaways
Industry Buzz
“What sets MG apart is variability—patients may be normal in the morning and symptomatic in the afternoon, or after prolonged use of their eyes.” — Min Kang, MD, director of the myasthenia gravis clinic at UCSF
“One major thing everyone should remember is that myasthenic double vision, or double vision in myasthenia, is only present when both eyes are open.” — Payam Soltanzadeh, MD, associate clinical professor of neurology who specializes in neuromuscular disorders at UCLA
“Things like amblyopia (lazy eye), things like glaucoma … corneal diseases, eye muscle disorders, thyroid disease that affects the muscles around the eye—I’ve seen that confused with ocular myasthenia.” — Rodrigo Rodriguez, MD, neurologist with Keck Medicine of USC
Myasthenia gravis (MG) impacts 36,000 to 60,000 people in the US.[] Yet one of the most common early symptoms, double vision (diplopia), can sometimes be mistaken for other causes.
“Diplopia is a common presenting symptom of MG, particularly ocular MG, but it’s often attributed to refractive errors, cranial nerve palsies, thyroid eye disease, or even microvascular ischemia in older adults,” Min Kang, MD, director of the myasthenia gravis clinic at UCSF, tells MDLinx.
“What sets MG apart is variability—patients may be normal in the morning and symptomatic in the afternoon, or after prolonged use of their eyes. That diurnal fluctuation and fatigability are often missed unless specifically elicited in history or through fatigue testing,” Dr. Kang says.
Symptom explainer
Nearly 50% of patients living with myasthenia present initially with only ocular symptoms.[]
These may include double vision (diplopia), fluctuating ptosis (variability in drooping eyelids), and orbicularis weakness (difficulties with closing the eyes).
But there are distinct symptoms that set myasthenia apart from other eye conditions.
"One major thing everyone should remember is that myasthenic double vision, or double vision in myasthenia, is only present when both eyes are open."
— Payam Soltanzadeh, MD
“If you close each eye, either eye, the double vision should go away,” explains Payam Soltanzadeh, MD, an associate clinical professor of neurology who specializes in neuromuscular disorders at UCLA. “So if that doesn't go away, if the double vision is present with only one eye open, then it cannot be myasthenia. And you should think about things that are related to one eye, or we call them ocular, meaning that they might be a refraction problem… So they definitely have to see an ophthalmologist.”
Ocular myasthenia gravis
Ocular myasthenia gravis (OMG) is a distinct form of myasthenia that is typically characterized by nearly exclusively ocular-based symptoms.[]
In 20% to 60% of OMG cases, the disease can evolve into generalized MG.
There are challenges in diagnosis for both generalized MG and OMG. There are no standard diagnostic criteria for OMG, and diagnosis is reached based on relevant symptoms and a positive result for certain autoantibodies.
But whether due to OMG or generalized MG, eye symptoms due to myasthenia are often mistaken for other causes.
“Things like amblyopia (lazy eye), things like glaucoma…corneal diseases, eye muscle disorders, thyroid disease that affects the muscles around the eye—I’ve seen that confused with ocular myasthenia….Sometimes even cataract, because of the refraction off of the orbit leading to double vision, can also be confused with ocular myasthenia. So a whole host of ocular ophthalmologic conditions,” Rodrigo Rodriguez, MD, neurologist with Keck Medicine of USC, tells MDLinx.
Myasthenia gravis must be considered
Dr. Kang argues that physicians need to consider a diagnosis of myasthenia gravis any time a patient presents with variable double vision.
“MG should be in the differential diagnosis when fluctuating diplopia or variable kind of diplopia is present. For instance, if a patient has symptoms with alternating eyes, or a change in degree of separation or angle (vertical, diagonal, or horizontal), this would be very suggestive of fluctuating diplopia due to MG,” she said.
“Many clinicians still perceive MG as a rare disorder, or are unaware of ocular MG as a distinct subtype. Improved continuing medical education and targeted clinical decision support tools could help close this gap.”
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