Myasthenia Gravis

As a neuro-ophthalmologist  and oculoplastic surgeon, I get to see people with a variety of  multiple complaints. As previously discussed one complaint that we often get is double vision. I also get patients sent over for evaluation of droopy eyelids (ptosis). Often the double vision is a small stroke, thyroid eye disease, or other damage to the muscle, but occasionally  this can be secondary to a disease called myasthenia gravis.

This is also true for the droopy eyelids. While most of the time the cause is the muscle getting weaker or slipping off its natural attachment point (which is repaired surgically by an oculoplastic surgeon like myself), the eyelid problem can also be from myasthenia gravis.

What Is Myasthenia Gravis

The way muscles work is that they are told when to fire by a nerve. The muscle and nerve do not actually touch. Rather the nerve releases a chemical called acetylcholine that is then detected by a receptor on the muscle. When the muscle senses the acetylcholine the muscle goes to work.

The problem in myasthenia gravis, is that the body produces an antibody (similar to the ones made by our body to combat infection) that attaches itself to the muscle receptor. This blocks the muscle from being able to tell if there is acetylcholine around. So with no stimulation to work the muscle does not fire. Usually not all the receptors of the muscle are blocked which is why at first the muscle may work fine but after a few minutes of use it starts to work less.

I like to think of it as the muscle have a bunch of light switches that when turned on make it work and that the antibodies stop the switches from being activated. Sometimes the disease will only affect the eyes and sometimes it can affect the entire body.

Symptoms of Myasthenia Gravis

Patients with myasthenia gravis often complain of increasing weakness or fatigue that gets worse the more they do of an activity. In my world the patient will often say that when they wake up there is no double vision and or droopy eyelids, but very soon or sometimes later in the day the symptoms start and continue to get worse until they rest again. This can not only occur with the eyes but also with the arms, legs, and even the lungs (difficulty breathing can be a sign since the diaphragm is a muscle).

Diagnosis of Myasthenia Gravis

The diagnosis can sometime be very straight forward or a challenge. There are some blood test that look for the antibodies, but these are not always detectable. Tensilon is a medication that can be injected into a vein and will temporally reverse the weakness showing it was due to myasthenia gravis.

Even a test that just allows the patient to rest, or put ice on droopy lids can help make the diagnosis. This is why it is important to see a doctor who is use to working up patients with possible myasthenia gravis. Patients also will need a CT scan of their chest to look for a fatty tumor called a thymoma that can be the producer of the antibodies in about 10% of the patients with myasthenia gravis.

Treatment Of Myasthenia Gravis

Myasthenia is most often treated medically. This can be done with a medication called mestinon. This increase the amount of  acetylcholine around the muscle be stopping its breakdown after release from the nerve. This essentially turns up the volume from the nerve to the muscle (it goes to 11).

Medications that decrease the amount of antibodies present, such as prednisone, are also used to help free up some of the receptors. Often different combinations of medications are needed to help control the patient. There are drops that can even be used to help improve the eyelid height.

If a thymoma is found and is removed the patient can possible have resolution of the disease and not need long term medication treatment.

I hope this gives an oversight of what myasthenia gravis is and what can be done to help treat it.

Jody Abrams, MD

Oculoplastics/ Neuro-ophthalmology

Sarasota Retina Institute

Sarasota, Florida 

 

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  1. […] the muscle and pull it off the tarsal plate. There are neurologic causes of droopy lids such as myasthenia gravis, brain strokes, cranial nerve 3 damage,  other neuromuscular disorders.It is important to see your […]

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