Myasthenia Gravis: Diagnosis (Nursing)

by Rhonda Lawes, PhD, RN

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    00:00 How do you determine if a patient really has myasthenia gravis When you get the phone call and someone asks you about these symptoms, you're gonna recommend that they go see a healthcare provider.

    00:10 But this is what they can expect when they go see their healthcare provider if this is a suspected diagnosis.

    00:16 They'll do a physical and neurological examination.

    00:19 They'll do a tensilon test, a blood test.

    00:22 They'll do some electro diagnostics, diagnostic imaging, pulmonary function testing, and they'll do a ice pack test.

    00:28 So we've got these options that we can look at and that the healthcare provider is likely to do to determine the diagnosis.

    00:36 So, first up, it's a physical and a neurological examination.

    00:40 Now you're very familiar with this, but the physician will review the individual's medical history and they'll do a full physical examination.

    00:48 Now in the neuro exam, the physician will look at their muscle strength and their tone, their coordination, their sense of touch, and look for any impairment, particularly, in eye movement.

    00:59 Neurological assessments are very consistent.

    01:01 But in this one, they'll be really looking for any problems with symmetry and any problems with eyelids in particular called “ptosis.” Now this edrophonium test, that's another fun word as to say, that's why I call it the tensilon test.

    01:16 It's a lot easier.

    01:18 Because this is what we're doing. If the patient is experiencing these symptoms.

    01:23 The test uses an injection of tensilon.

    01:25 It's a lot easier to say than edrophonium.

    01:28 So we use tensilon, it's injected.

    01:31 And if the weakness in the patient is relieved, then we know it's likely myasthenia gravis.

    01:36 Okay, so how does injecting something relieve that? Well, this drug tensilon, particularly blocks the breakdown of acetylcholine and it temporarily increases the levels of acetylcholine at the neuromuscular junction.

    01:52 Okay, stop for a minute and think back. We had that really cool drawing.

    01:56 In fact, if you want to look back in your notes at that as we're talking through, that's good, too.

    02:01 But remember as the impulse travels down the nerve, it tells the nerve to release acetylcholine into the junction.

    02:10 When it releases that acetylcholine into the junction in healthy, normal areas, it would attach the acetylcholine receptors.

    02:18 Well, this drug will provide extra acetylcholine because in myasthenia gravis, those receptors are kind of messed up.

    02:24 So, temporarily, if we use this drug, there'll be extra acetylcholine available, you should see a resolution of those symptoms.

    02:34 So we usually use it to test if the patient is having the eye symptoms.

    02:38 So when you hear tensilon test, that means we're injecting the patient with this medication, and it should help increase the levels of acetylcholine at the neuromuscular junction, and their eye paralysis or those sagging droopy eyelids should be resolved temporarily.

    02:56 Now we can't keep giving this to the patient, it's just used for a test.

    03:01 The test is no longer used in the US due to a high number of falls positive Now a blood test is the most common method for testing We do have some blood tests, won't be as dramatic as what you see with the tensilon test.

    03:14 But a lot of people with myasthenia gravis have some abnormally elevated levels of acetylcholine receptor antibodies.

    03:21 So that second antibody we talked about, the anti-MuSK, sounds like a way to keep away junior high boys, but the anti-MuSK antibodies also been found in about half of the people who have myasthenia gravis who don't have the acetylcholine receptor antibodies.

    03:36 But here's the bad news, a blood test can detect the antibodies, but some individuals with myasthenia gravis don't have either one of those antibodies.

    03:47 So, go back up to the first point, make sure you underline acetylcholine receptor antibodies.

    03:53 Go into the second point and underline anti-MuSK antibody.

    03:58 So when you're looking our third point when we talked about how some patients don't have either of these antibodies, always remind yourself of the two we're talking about: acetylcholine receptor antibodies and anti-MuSK antibodies.

    04:11 These people are called seronegative.

    04:14 So underline that word, it means negative antibody myasthenia.

    04:19 That means we can do a blood test on these patients, but they're not going to have either one, acetylcholine receptor antibodies, or the anti-MuSK antibodies that are visible.

    04:30 So blood test is a shot.

    04:32 It might tell us something.

    04:34 But even if it comes back negative, that wouldn't confirm that the patient doesn't have myasthenia gravis.

    04:40 Okay. We're three tests in.

    04:44 Pause the video for just a second and see if you can quickly run through the three tests we've just talked about, and what they would tell us about a patient with myasthenia gravis.

    04:59 Okay, good job. We're at the halfway mark.

    05:02 You've done review the three first tests.

    05:05 Now we're gonna go through four, five, and six.

    05:08 Now this one is a little unusual.

    05:11 I don't think I really enjoyed this test if I had to have it done.

    05:14 It uses repetitive nerve stimulation.

    05:18 Okay, so it repeatedly stimulate a person's nerves with small pulses of electricity.

    05:23 Yeah, you heard me, small pulses of electricity.

    05:27 I know we call them small, but it's still not very comfortable.

    05:31 And the goal is to just wear out very specific muscles.

    05:35 That's why they use small pulses and they use electricity.

    05:39 They're just gonna wear out the muscle.

    05:41 Because muscle fibers in myasthenia gravis, as well as some other neuromuscular disorders, don't respond as well to repeated electrical stimulation as compared to muscles that have normal-- from normal individuals.

    05:54 Okay, so first one, got the idea? We're gonna use small electrical impulses and we're gonna hope that we could just work at it till we tire that muscle out, and we'll be able to recognize if the patient has myasthenia gravis, their muscles will not respond as well to the repeated stimulation because you're just wearing things out.

    06:14 Remember how the nerve to muscle works.

    06:16 Eventually, you're gonna wear, run out of things, because they don't have the receptors to follow along a normal nerve stimulation.

    06:24 Well, that's one way we can do it.

    06:26 Now there's also a single fiber electromyography, EMG.

    06:31 Now I went to one of these with my mom and I really was sure I don't ever want to have one of these.

    06:36 It's really not that bad, but I don't think I want to sign up for one.

    06:41 This is the most sensitive test for myasthenia gravis.

    06:44 So this one is better than what we just discussed.

    06:47 So make sure you star this and say that this is most likely what the health care provider will order if it's available.

    06:53 So, it's a single fiber EMG.

    06:56 It is the most sensitive test from myasthenia gravis.

    06:58 It detects impaired nerve to muscle transmission.

    07:02 So an EMG can be really helpful in diagnosing mild cases of myasthenia gravis when the other tests don't.

    07:09 So remember, put a star by this one.

    07:12 If I was concerned that I had myasthenia gravis, this would be the test.

    07:16 Even though I wouldn't like it, this would be the test that I would want to see done.

    07:20 Now we can go to diagnostic imaging.

    07:22 Okay, before you read the slide, stop for just a minute, think about what we know about myasthenia gravis.

    07:30 Why would we go to a CAT scan or an MRI? What are we gonna look at? We're not gonna X-ray their eyelid, right? Oh, thymoma.

    07:40 Yeah, that's what a cat scan or an MRI might show us.

    07:43 That thymoma, right? Now they may or may not have it, but this would definitely determine if they did or did not.

    07:51 Now where is the thymus gland located? Right, behind the breastbone.

    07:57 When is the thymus gland the biggest? Looking at lifespan, when is it the largest? Right, relatively when I'm a little kid, and then as I as I progress through puberty, it keeps getting a little bit bigger.

    08:10 So, it should get smaller as an adult and be replaced with, what? Yeah, the sad news, fat.

    08:17 All right, the sixth one, pulmonary function testing.

    08:22 Now this one is just gonna help us give us an idea of what the patient's respiratory status is, how it's doing, how strong they are.

    08:28 Because measuring breathing strength can help predict if the patient may be leaning towards a myasthenia crisis and have trouble with respiratory issues.

    About the Lecture

    The lecture Myasthenia Gravis: Diagnosis (Nursing) by Rhonda Lawes, PhD, RN is from the course Chronic Neurological Disorders (Nursing).

    Included Quiz Questions

    1. Eye movement
    2. Muscle coordination
    3. Sight acuity
    4. Reflex responses
    1. Edrophonium (Tensilon) test
    2. Anti-acetylcholine test
    3. Ocular responsiveness test
    4. Single fiber test
    1. Single fiber electromyography (EMG)
    2. Tensilon test
    3. Blood antibody tests
    4. MRI
    1. Presence of a thymoma
    2. Plaques in the brain
    3. Neuronal damage
    4. Nerve conduction difficulties

    Author of lecture Myasthenia Gravis: Diagnosis (Nursing)

     Rhonda Lawes, PhD, RN

    Rhonda Lawes, PhD, RN

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    Thank you Rhonda!!
    By Rav A. on 16. January 2021 for Myasthenia Gravis: Diagnosis (Nursing)

    Rhonda Lawes is the best Instructor. She makes the content so interesting and engaging!!