Section: CME Category: Medicine & Pharmacology Neurology

Review of Neuromuscular Diseases

Wenjay Sung, DPM

Wenjay Sung, DPM discusses the basic pathophysiology and clinical presentation of patients with neuromuscular disease, methods for diagnosing, and how these diseases present in the lower extremity.

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Goals and Objectives
  1. Define the basic pathophysiology and clinical presentation of patients with neuromuscular diseases
  2. Review the advanced imaging options used to diagnose neuromuscular disorders
  3. Relate neuromuscular disorders to how they present in the lower extremity
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  • CPME (Credits: 0.75)

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    PRESENT eLearning Systems, LLC has approved this activity for a maximum of 0.75 continuing education contact hours.

    Release Date: 11/21/2018 Expiration Date: 12/31/2020

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    Wenjay Sung has nothing to disclose.

  • Lecture Transcript
  • TAPE STARTS – [00:00]


    Male Speaker: We're going to have an interesting talk on neuromuscular disorders and disease, which we don’t necessarily hear about or think about that often, or that much, but it definitely has impact on our practice. And you will see patients who suffer from some of these things. So please welcome Dr. Wenjay Sung to share his thoughts on that.

    [APPLAUSE]

    Sung: Thank you Dr. Sean House [phonetic] [0:00:27], thank you again at present [phonetic] for inviting me. And this is, again, more of a review if anybody's taking Boards coming up or if you'd like to get an update with your clinical practice. It's again, not very common to see this in our podiatric offices. I rarely see a lot of neuromuscular disease, but you may see this every now and then, so it's a good review for those who are residents taking Boards or would be just like a good update. I have no disclosures for this presentation.

    So we’re going to talk about disorders of the motor unit. There’s several different types. We’re going to focus on peripheral nerve disorders, motor neuron disease, neuromuscular junction disease and also muscle disease in general. With the peripheral nerve disorders, there's a few different types, mononeuropathy. I'm sure if you do some billing, those pop up on your ICD-10 updates. So mononeuropathy means a pattern of weakness and sensory loss, conforms to one single nerve distribution. So again, mononeuropathy makes sense if you know the Latin, and it’s pretty much carpal tunnel or tarsal tunnel, peroneal nerve palsy, even a neuroma is considered a mononeuropathy.

    Now a mononeuritis is different. Mononeuritis has multiple nerves affected in a random pattern. Diabetes is actually one of the most frequent of them. Vasculitis also has mononeuritis symptoms. So it's something to be aware of the difference between mononeuropathy and mononeuritis.

    [2:02]

    Also, polyneuropathy. This is where we tend to hear more often, it's more distal symmetrical. But polyneuropathy can affect different nerve fibers; autonomic, motor, and sensory. We're going to focus on the sensory because a lot of different things with the autonomic and motor, we're going to talk about those as well. Right now, sensory nerve fibers are usually large, well-myelinated, but some are small or poorly myelinated, especially with the sensory nerves. You guys remember the tracks back in neurology class. Other symptoms of polyneuropathy; it usually starts in the feet, and we’re talking about for podiatrists, so it starts in the feet and moves proximally. Again it happens also in the hands and sometimes they also feel it in the knees as well, but it’ll tend to get more distal before it goes approximately. You have some tingling, some pins and needles, some burning, also numbness and deadness. So it's like I'm walking on thick socks. It’s very, very common.

    Exams of peripheral neuropathy. Usually with sensory impairment. We also have some tactile impairment, distal glove and sock distributions. Also vibratory disturbance and also using that tuning fork that we all remember.

    These are some bedside tests you can do clinically. You can do also inpatient-wise. I'm sure we all know monofilament. Myotatic reflexes, deep tendon reflexes, vibrational and thermal, you can use this just with your pen light. Now, obviously we see a bunch of diabetic females with also ulcerations.

    So other clinical features of polyneuropathy are atrophy of the distal musculatures. You see the pes cavus before me, as the gentleman before was speaking on that. People tend to walk more on their heels. You see that peek-a-boo sign from the back. So you’re looking from the back and kind of see like a little peek-a-boo sign, some subtle cavovarus deformity. Also, what's interesting is that they have normal muscle strength more proximally, so their hips and their core is little more stronger than obviously they're distally. So hereditary-wise we kind of see this when we associate this with CMT, Charcot-Marie-Tooth.

    [4:20]

    Other classifications of polyneuropathy, whether it's pure sensory, pure motor; the types of fibers involved; whether it's by pathology; whether it’s demyelinating, axonal or mixed type; and then by tempo, acute, subacute and chronic. What did I mean by that? Well acute polyneuropathy is Guillain-Barré, I'm sure we remember that from neurology class. Also poly porifera, which can be sometimes associated with psychiatric disorder and also unexplained GI complaints and toxins. Toxin-induced polyneuropathy, whether glue sniffing or arsenic or heavy lead poisoning.

    So Guillain-Barré syndrome, again, was discovered by these three gentlemen. And it's most commonly described, especially when Boards, as a rapid ascending, progressive weakness. So rapidly ascending progressive weakness, those are your key words for the Boards. Also demyelinating neuropathy, ascending weakness which also includes the cranial neuropathy. Exam reveals a symmetrical weakness, so it's on both sides, not just one leg, not just one toe, not just one finger, but again, this is symmetrical ascending neuropathy. The bowel and bladder are actually usually preserved. However, I've had a patient with Guillain-Barré, went all the way up to his neck, he had to go on a ventilator and then it disappeared. Nobody really knows why it happens or when it happens, but when it does, it can be very dangerous, but it tends to go away.

    Respiratory failure again can be precipitous, other causes morbidity and mortality. They can get DVT and they no longer function, they no longer are moving. There is autonomic instability that can lead to infection also because they do have, especially sacral wounds and bedsores. Immune mediated, maybe also post infectious. So be aware of that. Treatments usually a plasma exchange, also making care of good bed care. Palliative care is also very important and intravenous immunoglobulins.

    [6:28]

    So subacute polyneuropathy, these also include vasculitis. Paraneoplastic is a cancer-induced neuropathy. Now it's not cancers affecting the nerves, I want to make sure people understand this. This is very different. Paraneoplastic neuropathies are actually when someone has cancer, the immune system starts attacking everything and then attacks the nerves and that's what paraneoplastic syndromes are about. So it's not again, cancer attacking the nerves. It’s immune system reacting to the cancer and then reacting to the nerves as well. There’s chronic inflammatory demyelinating polyneuropathy, again toxins and drug induced, subacute.

    So another thing with chronic polyneuropathy, these are more what we more commonly see. We see in our clinics, diabetes, renal failure, chronic liver failure, thyroid disease. These tend to be something that we more see in our clinics and we deal with nutritional vitamin B12 deficiency. See that’s mostly with again, sailors or people who tend to also take metformin. This tends to be one of the side effects of metformin, a vitamin B deficiency.

    Infectious disease can also have polyneuropathy, HIV, leprosy, Hansen's disease; as also could be inherited, as we talked about Charcot-Marie-Tooth.

    [8:00]

    Now evaluation. There’s a lot of different ways to evaluate lab works. Also very important to rule out a lot of different things with lab work, blood work. Are you going to be here tomorrow? I’ll talk about some interpretation of blood lab work tomorrow. So I'd be interested in being connected to this lecture.

    There's also nerve conduction studies, electromyography, to distinguish between what's axonal and what's demyelinating. And also it helps ascertain with certain severity. What's also interesting is that you also with an EMG, you can distinguish between what's myogenic and neurogenic. And we'll start talking about the difference between whether it's starting from the nerve or actually starting from the motor unit, we'll talk a little more about that. Then you can possibly get a nerve biopsy, to kind of get a better idea. Now, do we all need to do this? Obviously not. Not that bad of an idea, just referred to a neurologist or infectious disease, especially if it's a coming from a different area. However, you know, it's not a bad idea to get a nerve biopsy in certain cases.

    Now, again, electromyography, functional diagnostic method. Some people may do this in their office. I know there's a lot of different vendors that may provide this in your office, you do EMG or NCV in your office. It's really not that difficult. You just strap on these in case on certain locations and you're able to conduct conduction study of the peroneal nerve. Same thing with the sural nerve over here, able to start reading it out. And again, these are billable as well. But the main thing is if you know how to read this, good. If you can't read it, there's no point to get it. So understand you can do this in your office. And again, there's different vendors that help provide that, but I do recommend getting a background before you actually start doing it.

    These are what the needle electromyography electrodes look like. They're going to go a little deeper.

    [10:06]

    So, what I talked about earlier with myogenic lesions and also neurogenic lesions is how they look on EMG or ENG. So you can see this is how a myogenic lesion looks like. When you go to a neurogenic lesion, you see the big difference in how they look and the wavelengths.

    It’s kind of like an EKG for me, I can't really read it but I can see there's something wrong. So if something wrong there, send it to neurologist, that's all I really know. Send it all. Send it to neurologist, but you can see the difference. So just knowing the differences, you know, if it's a myogenic means coming from the muscle unit, or coming from the nerve. So knowing the difference, you know what to start treating and start to be a detective about.

    Now we're talking motor neuron disease which is again another disorder of the motor unit. So motor neuron disease, these are involved with the best cells of the motor cortex or the lower CN motor nuclei, the CNS and also the anterior horn cells of the brain. About 80% of these types of diseases are ALS, Lou Gehrig's disease. About 10% are progressive bulbar palsy, which actually affects muscles, progressive muscular atrophy, spinal muscular atrophy, and then primary lateral sclerosis. Those are more rare obviously, even more rare than ALS. So, this is what ALS kind of looks like, which is some of the research with ALS is producing. We know it starts affecting these areas of the brain, the micro ganglia, astrocytes, also the buildup with certain proteins in the transport tubes.

    [12:01]

    So we started noticing and researching more with ALS. However, we still don't know how it occurs. We do know what some of the symptoms are, but we don't know how it progresses, how it stops, how it originates, and what the true etiology is or causation. But we do have some newer treatments for it.

    ALS is very rare, it's only about 4% to 6% out of 100,000. The incidence is even lower. Most of ALS, there's no family history, about 90% to 95%, so it's kind of scary. You don't know and it just comes up. People with the familial history is actually less likely. First symptoms again are in your limbs, sometimes gets some motor involvement as well, around the [Indecipherable] [0:12:48] systematic nerves, about 25%, that's what usually occurs, but usually you get it from the limbs, start getting weakness, usually more in the upper and the lower.

    Now, for Boards, what's important is that it’s a mixed upper motor neuron and lower motor neuron finding. So it's a mixed finding, not just upper motor neuron lesion or lower motor neuron lesion, it's both and that is a number one Boards thing. So those who are studying for Boards or residents, just remember that, it's a loss of motor neurons to the cortex, brainstem and spinal cord. So weakness, atrophy, fasciculations, you'll get all that as well as slurred speech, difficulty swallowing, and shortness of breath. Again, it can also start with any extremity of the bulbar musculature and it's relentlessly progressive.

    So prognosis, about half people die within three to five years, about 80% are dead in five years, and less than 5% live past 10 years. Stephen Hawking's been probably most famous person with ALS, other than Lou Gehrig. He lived for decades. If you've seen this movie, it's a great movie, great portrayal of his life. So it's actually really heartwarming, but a lot of people have ALS that did not have the same funding as Stephen Hawking. So we'll get to that in a little bit.

    [14:12]

    Remember the Ice Bucket Challenge. Remember all that? They raised a few million dollars, I think like $10 million, using Ice Bucket Challenge, and from this they actually discovered new treatments. So, even though you know, Stephen Hawking, he lived a long life, majority people with ALS do not. And a lot of them suffer through ALS.

    Some of the diagnostic algorithms for ALS include, obviously getting an MRI of the brain and C spine, evaluating the spinal fluid. Clinical symptoms, again, an upper motor neuron lesion and a lower motor neuron lesion. So, again, getting an EMG or NCV is very important, if you start suspecting that in your patients. Again, sometimes you might get a paraneoplastic exam, meaning there may be a cancer induced form of ALS; however, again, that's quite rare.

    Again, causative treatment, we don't know what causes ALS. So there's no way to actually say this is how we're going to prevent it by doing this; if you do A, B and C, we’ll prevent D from happening. There's no causative treatment at this time. There are no protective treatments, we can try to slow it down. However, again, these are all still in clinical trial phases, different vitamins, antioxidants, boosting different studies. Really, most of it is just palliative treatment. The most important treatment we have for ALS, being palliative; mobility, using sticks, wheelchairs; being multifunctional bed. Nutrition obviously is very important, a lot of people can't swallow. Communication, as you remember, Dr. Stephen Hawking had a voice communicator because he lost his voice a long time. Even though he lived for decades, he lost it quite young. Using books and tables and so forth. They actually have an EyeWriter communicator now.

    [16:13]

    I had the privilege of attending this business forum and the guy who invented the EyeWriter, which is basically, he went to Venice Beach and got one of those cheap sunglasses and then built and created following the eye movements, and people were able to write with their eye, because that's all they had movements left. So it's called the EyeWriter. If you look at that, it's actually quite helpful for people who can't even use their hands. Stephen Hawking still had use of his hands, so that's why he was able to use that voice communicator with the keyboard. Some people don't even have that, all they have is their eye. So they have this thing called the EyeWriter so they can write using their eye, which is pretty cool.

    Anxiety depression. Obviously if you had ALS, this is quite sad. Christian Bale plays this movie called Rescue Dawn and it was this, I think, Vietnam War veteran who escaped capture in Vietnam. It was a great life but he developed ALS. This is a guy who survived ’Nam, survived capture, and was in the jungles of Vietnam for like weeks and still got rescued, but developed ALS and killed himself right after, and this guy survived everything. So obviously depression, anxiety, something that would be concerned with people with ALS.

    Respiratory syndrome. Again, that can happen obviously, as everything there starts progressing. And again, it's a very full family care. So ALS doesn't just affect the patient, obviously it affects the family as well.

    Treatments. Again, stem cell therapy. All these are still ongoing. There’s some positive studies. There's really no EBM, there's really no evidence based medicine at this time. However, there are several ongoing studies funded by the Ice Bucket Challenge, believe it or not, so that actually did help a lot.

    [18:02]

    Now we’ll talk about muscle disease. So there's different types of muscles diseases, hereditary muscles disease and acquired muscle disease, muscular dystrophy, muscular channelopathies. Other mitochondrial myopathies and metabolic myopathies, and inflammatory myopathies, infectious muscle disease, and so forth. So we'll talk about some of the symptoms of muscles disease.

    General muscle fatigue, seems like everybody has muscle fatigue, but muscle fatigue is a symptom of just exercise intolerance in general, proximal and symmetrical weakness, and this is actually something you'll see more in children because it tends to pop up early in life. Remember the waddling gait. People having a hard time getting up and doing what's called the Gower’s sign. I'll show you some of that.

    Hyperextension of the knee, when they trying to get up. They don't have much good musculature. Increased lower doses of the lumbar spine, scoliosis and contractures, tight Achilles tendon. Sometimes they have a myelopathic face, muscular atrophy, the big fat calf, very weak calf. However, they had that pseudohypertrophy of the calves. Another kind of like a buzzword when it comes to the Boards, “pseudohypertrophy of the calf.”

    Myotonia, which actually means excitability. I remember being a student and saw that word, I always thought it meant weakness, it actually means excitability. So excitability of the muscles and tendons reflexes are generally normal or decreased.

    So, some of the things that we find when it comes to myopathies, are increased creatinine kinase levels due to many different myopathies, meaning muscle fiber necrosis is present. Again, a high creatinine kinase levels could also be a heart attack or liver damage. It could be damaging to your kidney. So that's why people, when looking at these labs, it’s very important to find yourself. Sometime they may need to go through dialysis because there's a lot of creatinine kinase in the blood.

    [20:00]

    ENG, the electroneurography test, EMG test, differentiate between whether it's a myogenic or neurogenic. It’s very important to figure out if it's coming from the nerve fiber or it’s coming from the muscle. Muscle biopsy may be required sometimes in this case, but now I think we do more genetic testing. So when it comes to hereditary myopathies and also other progressive weakness myopathies, we tend to do more genetic testing, rather than just doing a muscle biopsy.

    Muscular dystrophy. Duchenne’s Muscular Dystrophy or Becker's Muscular Dystrophy as well. We now have a genetic test for this, rather than just taking a muscle biopsy and actually putting a child through this, we're able to distinguish who may have this and who hasn't. Originally called, very difficult name to pronounce, dystrophinopathy. Again, described really early on in 1881. The gene was discovered in the ’80s; however, described really early about 100 years prior. Deficiency in the dystrophin protein, and progressive loss of muscle fibers. Becker’s type is more benign course; however, those with muscular dystrophy tend to die at a young age, around 30s. They again lack the dystrophin gene; therefore, they lack in the muscular building. So they get a lot of weakness and progressive loss of muscular fibers because of that. Onset usually at three to five years, that's with kids. You know we tend to see this again in children, and tend to be diagnosed early. It’s initial symptoms; very difficult from getting off, they waddle, climbing steps; most weakness is lower limb-girdle muscles, trunk, [Indecipherable] [0:21:53] muscles are spared; however, in the cranial bulbar region there are skill deformities.

    [22:01]

    The heart unfortunately also plays a big role. Their inability to walk generally by nine to 11 years. They may be able to walk at age one or two, get up; however, three to five they start showing some symptoms; and by nine to 11, they progress where they are wheelchair bound; and by the third decade, they usually die from a respiratory insufficiency.

    If you guys remember this from class, children, this is the Gower’s sign, unable to get up like a normal kid, straight up and bend at the knees, they can't do that. They have to use their arms to get up, Gower's maneuver.

    This is Becker's dystrophy. Again, they actually tend to be able to live a little further, it's not as morbid as Duchenne’s muscular dystrophy, but these are some of the symptoms. You can see some of the muscle changes in this young man.

    Myotonic dystrophy. This is one of the key Board point, that they're unable to release quickly. So inability to do a quick muscle release, that's why their hands are gripping and they can't release it. It just holds, and you try to get them to unhold and they can't. So it's caused by a DNA, repetition of CTG in chromosome 19. Prevalence about one in 8000. It's autosomal dominant. So you can anticipate if somebody does have it, that they're probably going to pass it on.

    Progressive muscle disease and weakening; even though there're hyperexcitability with their muscle, they're unable to release and they start getting other symptoms as well. Cataracts, again, closure of the vessels in the eyes, frontal balding, cardiac abnormalities, and also sometimes mental retardation.

    [24:25]

    Limb-girdle syndromes. This is, again, a lack of certain proteins, protein deficiencies that they're unable to generate. You can see some of the dystrophic changes to their body.

    Another dystrophy, as again, it's another autosomal dominant. However, even though they have these dystrophies and they're changing, this is not lifespan threatening, this particular one. Again, they start seeing muscle weakness in their face. Obviously, I blacked out the face. You can see the curvature of their back, you can see the weakness in their legs and also the scapula. This is what's the key. The scapular changes. If this is on your Boards, it's a scapular proximal changes, and you see how their winged scapula, it's like that. That's the key for the Boards. God forbid you get that on the Boards, this is not easy.

    Channelopathies. These are muscle channelopathies for the sodium, calcium and chloride channels. If there're channelopathies, this is muscle fibers and release. If you guys remember ATP and the channels, how we get releases with nerve signals. Sometimes the channelopathies and things were wrong with those sodium chloride or calcium. So the main channelopathy, what's important is malignant hypothermia. This is going to obviously kill you instantly. Other ones are important as well. Obviously, potassium-aggravated myotonia and so forth, but channelopathies again. These are quite rare, but you may come into contact with them.

    Myotonia congenita, these again are more of autosomal dominant form. Again, it's more of a genetic disease, muscle stiffness, abnormal muscle relaxation and warm up. Therapy is generally taking some medication to help with the symptoms; however, it does not obviously cure them.

    [26:07]

    Inflammatory muscles diseases include durapathy [phonetic] [0:26:08], myelitis, poly-myelitis [phonetic], inclusion body myelitis, and some autoimmune diseases. Dermatomyositis, these generally appear with a rash on the face, that's why it's called dermatomyositis. There're usually some cardiac abnormalities, sometimes orbital bleeding, orbital edema as well. These progress usually over weeks to months and again they're an autoimmune disease. You have the pain and proximal limb weakness of the muscle and the neck flexors. What makes it different from poly-myelitis is actually there's no skin deformities in poly-myelitis. So there's no skin response. However, it's very similar to dermatomyositis.

    So these are some of the things that you have to look for; a high creatine kinase level, muscle necrosis, muscle fiber necrosis. Again check that, because it maybe affecting their kidneys, and so forth. Myogenic findings; it's not neurogenic, it's myogenic when you're looking at the EMG. Getting a muscle biopsy if you see some inflammation, but we recommend genetic testing instead. Therapy is immunosuppression and also long-term treatments with corticosteroids.

    There’re also toxic myopathies, these again are drug-induced or heavy alcohol induced for a few days, and also heavy drug induced like heroin and steroids. These can also cause myopathies. There're different names for these as well. In fact, different things such as hypokalemia, adrenal insufficiency, hyperparathyroidism, and so forth. But now we're moving on to neuromuscular junction disease.

    [28:00]
    Myasthenia gravis is actually the most common and probably the most popular when you think of neuromuscular junction disease. It's an autoimmune disease that directly attacks the neuromuscular junction. These attacks are synaptic nerve fibers and it's usually one in 20,000 in the US. Women have a slightly higher incidence. However, men can have it as well. It’s usually fluctuating muscle weakness, excitability and flexibility. Some loss also in the facial drooping, and weakness in trunk and extremities. So usually you get the diagnostic algorithm, get an EMG, get a genetic testing, and then see some of the changes in the EMG.

    Treatment, again, plasma exchange, using IV immunoglobulin as well as corticosteroids to treat them. So when there's a crisis, again, from myasthenia crisis, this can be a paralysis of the respiratory muscles, so we’ll definitely get them assisted ventilation when required. Clinical symptoms that can have respiratory tract infection, respiratory failure; there’s loss of arms and muscle weakness. Some of the complications of the crisis and the treatments, as we talked about earlier, monitoring and antibiotics, sometimes respiratory rehabilitations required. Outcomes are usually high hospitalization rate with these patients.

    Thank you.

    One of the things I like to do and with my lectures, is, this is a QR code obviously, but if you take your camera phone, if you have signal, just open your camera and just focus on that. There's a link that should popup. If you want to keep this lecture for your review, you can. Just take your camera phone, whatever phone you have, it doesn't matter. If you have a smartphone, take your camera phone, focus on that, and a link should pop down. That link will give you my lecture and you can keep it.

    [30:04]

    Alright, so if you fell asleep, I'm sorry. You can read it later. Thank you.

    [APPLAUSE]

    TAPE ENDS [0:30:18]