MG Is More Than Just General Fatigue

Welcome, everyone. I'm Dr. John Whyte, the Chief Medical Officer at WebMD. Today, I want to discuss myasthenia gravis. It's a rare autoimmune neuromuscular disease that causes weakness and fatigue of voluntary muscles.

Essentially, antibodies cause a breakdown in communication between your nerves and your skeletal muscles. And it's usually around the eyes, mouth, the throat, and our arms and legs. There is no known cure, but there are effective therapies. The key is to recognize the signs and symptoms and get the right diagnosis early on.

Helping me to break it down are two experts, Dr. Pushpa Narayanaswami. She's the Associate Professor of Neurology at Harvard Medical School, Beth Israel Deaconess Medical Center. And Dr. Donald Sanders, he is Professor of Neurology at Duke University School of Medicine. Doctors, thanks for joining me.

Dr. Pushpa, let's start with you. Remind our viewers, what are we talking about when we mention and discuss myasthenia gravis?

The name is actually quite self-descriptive. "Myas" is muscle, "myo." "Asthenia" as weakness. So it's a mixture of Greek and Latin actually, which is an interesting piece of history that I like to know. And "gravis" means serious, so it's serious muscle weakness. That's the literal definition or literal meaning of the term myasthenia gravis.

So people with myasthenia gravis present obviously with muscle weakness, but the characteristic of this muscle weakness is its variability, its fluctuation, that we use the term fluctuation. And what does that mean? It means that many patients will be fine when they wake up in the morning. They don't have any symptoms. Or when they wake up after a nap in the daytime, they're fine. But then they go about their day, and they develop symptoms. And the symptoms they develop are often in the muscles that they use the most.

So they use the muscles, so they're driving, they develop droopy eyes, they develop double vision. Once they stop driving and close the eyes for a few minutes, they feel better, the symptoms go away. So it's use-related weakness of the muscles, also called fatigability. So there's a fluctuation during the day, which means it gets worse as the day goes.

What's the latest in our thinking of the epidemiology of myasthenia?

Well, it can affect any one at any age. But the predominant age of onset in women is early, in their 20s and 30s. Whereas, in men, the most common age onset is in later years, after age 50 or 60.

Dr. Pushpa, a lot of people are listening and thinking, I get tired, I get fatigue. Sometimes, I have some vision problems late at night. When do they start to think, hey, I need to go to the doctor and talk about my symptoms? And what's the doctor going to do in terms of testing?

Yeah. That's a really important question. And what you're getting at, John, is sort of the difference between fatigue and fatigability. And you have to sort of bear in mind that patients with myasthenia gravis can get tired, too. They can get fatigued. But what we're talking about is this fatigability which is, as I mentioned earlier, use-related weakness of a muscle.

So it's not that generalized feeling of tiredness, where I feel weak overall. I can't get myself out of bed. I just cannot bring myself to go to work. Or I need to come back from work and just lay on the couch. That's usually not the symptom that we worry about in myasthenia because that's a general sense of fatigue.

And there are multiple reasons for that kind of fatigue. What we worry about are patients who say, you know, I'm doing my hair--

Right. Brushing my hair, that's what I would always remember from exams.

Exactly. There you go. Exactly. I'm doing this for a while. And after a while, I just can't hold my hair dryer up, or I can't hold my brush up. So that is one aspect of it. The other thing is chewing, for instance. One of my patients once said to me, he said, Doc, I want to be able to eat my roast beef sandwich, because he couldn't chew the roast beef sandwich. He was able to eat a soft diet, but he got sick of his pureed diet, and he got sick of mashed potatoes. He wanted his roast beef sandwich because he couldn't chew it. The longer he chewed it, his jaws would get tired.

Which is that fatigability of the muscle as opposed to generalized fatigue.

Exactly. So that's it. So the second part of your question is, what do I look for when I see a patient who comes in and I'm wondering, does this person have myasthenia gravis? You have oftentimes this sort of progression of symptoms starting in the eyes and then maybe spreading to other parts of the body. And how they spread to other parts may vary. But it's not infrequent that myasthenia gravis starts with eye symptoms.

So to ask them about drooping of the eyelids, to ask them, as you're reading a book, what happens? Do your eyes blurred? Do you have to-- and sometimes, patients will actually tell you. They say, it gets blurry, then I close one eye, and I read, and it's OK, which means you're probably having a little double vision. And they're closing one eye, reading with one eye, and they get better. So I'll ask them, a good question that I found useful not just in the diagnosis but in following patients is, do you cough with meals? When you're eating, do you cough?

And then I'll ask them about all of these, do your hands arms get tired? You spoke about the hairbrush, all of those questions. So I try to get at that. And in my exam, in addition to just the muscle strength exam, what I'm trying to do is to tire out a group of muscles and see if they get weak. Does their speech get slurred after a while? And then have them hold their arms to the side for maybe three or four minutes and see if they get weak. So these are all things that I look for.

Dr. Sanders, do you do any lab tests to either rule out other conditions or confirm what you're suspecting before you go into other types of studies, such as electrophysiology or an EMG?

There are two tests that we do. One is called repetitive nerve stimulation, when we repetitively stimulate a nerve going to you muscles, let's say, a hand muscle. And we will examine the amplitude, the size of the response that we get with the nerve stimulation. The other electrodiagnostic tests we do is called single fiber EMG or measurement of jitter. And this is a test performed with a needle, in which we examine the time relationships between impulses from individual muscle fibers and the relationship between muscle fibers that are belonging to the same motor unit that are activated by the same nerve axon.

Typically, when more than one of these firing, they fire with a very constant time relationship. But when there's abnormal neuromuscular transmission, the time relationship between these impulses varies like this. And that is known as the neuromuscular jitter. And the jitter is a highly specific and very sensitive manifestation of abnormal neuromuscular transmission that characterizes myasthenia gravis. So those two tests help to confirm our clinical suspicion that we're dealing with an abnormality of neuromuscular transmission.

Dr. Pushpa, what's the impact of myasthenia gravis on people's quality of life? Is it something that's occurring every day? Is it something that is well-managed? What's the outlook?

Myasthenia senior has significant impact on quality of life and on activities of daily living. Uncontrolled myasthenia can affect them in almost all spheres of their lives, in their work, with your families, social, occupational, hobbies, you name it. So I think it affects them in multiple ways because of inability to do their jobs.

So clearly, a very serious disease and one that patients really need to recognize signs and symptoms and then talk about them to their doctor. I want to thank you both for joining me today.

Thank you, John.