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Video transcript

poliomyelitis also known as polio is caused by the polio virus now the polio virus causes a debilitating muscle disorder and this is caused by damaging neurons that extend from the central nervous system now the central nervous system is composed of the brain and the spinal cord now these neurons that extend from the spinal cord innervate or provide tone and responsiveness to the muscles of the body so the muscles of the arms are innervated and the muscles of the legs are innervated by motor neurons now polio affects these motor neurons causing damage to them and disability and as you can see over here this man with the cane actually was afflicted by polio when he was younger and has faced the consequences of the motor neuron damage his muscles in his right leg have atrophied or in other words they've lost their muscle tone and they've kind of shriveled up because without any input from the motor neurons they just shrivel up now another way to think of neurons are like electrical wires that provide electricity to your home if you shut off these electrical wires obviously your home will no longer have any electricity and so you can't power your home with the energy that you need from these wires the motor neurons act in the same way and you can no longer power your muscles from these neurons after the polio virus damages these motor neurons and so that's what happened to this man here now another prominent figure in history that was diagnosed with the polio virus was Franklin Delano Roosevelt FDR the 32nd President of the United States he was infected in 1921 which left him permanently damaged from the waist down but interestingly enough FDR didn't want to show the general public his ailment so there are actually very few pictures of FDR in a wheelchair now though he was diagnosed with polio it's now actually believed that he was misdiagnosed and that his symptoms were actually caused by something Gyan beret syndrome this would mean that his diagnosis of polio may have been one of the most prominent misdiagnosis in history now there's a few reasons that we believe he may have been afflicted by guillain-barre syndrome and that's for two distinct reasons most commonly polio affects children particularly children who are less than six months of age so FDR contracting polio when he's 39 is not very likely and second of all polio causes something called asymmetric paralysis asymmetric paralysis the muscles are damaged in a somewhat random process so having both legs damaged equally is unlikely I mean think about it the polio virus might affect the neurons on this side but the neurons providing energy to his left leg may not be damaged and so you might actually see what happened to our guy over here where his right leg is primarily affected Franklin Delano Roosevelt both his legs were affected and this is called symmetric paralysis and guillain-barre syndrome is known to cause this symmetric paralysis so how does polio in fact a person or specifically most likely a child under the age of six months so the virus usually comes in and enters through the mouth and actually starts goes down and starts replicating in the throat so it starts increasing in number and it can also travel down into the stomach and the intestines it might replicate in the intestines as well once the polio virus has increased in number somehow and we're not actually a hundred percent sure how it gets into the central nervous system into the spinal cord where it can damage the motor neurons that provide energy to the muscles now not everybody who contracts polio has this dagger dative damage to their motor neurons in fact 90 to 95 percent of people who are acutely infected are asymptomatic so they don't have any symptoms asymptomatic whereas about five to ten percent of people get only mild symptoms mild symptoms so what are the mild symptoms well these are symptoms that you generally see or can see with any virus you might get fever headache fatigue so this is really from your immune system trying to thwart the virus trying to fight it off so a patient might also have some throat pain and this is due to replication in the throat the patient may also experience abdominal pain stomach pain or nausea or vomiting and that's from the replication that occurs in the intestines patients that have these mounts impt ins generally recover and don't experience the muscle weakness in fact only about a half a percent of people who are infected acutely by the virus experience muscle symptoms and these muscle symptoms may include weakness right atrophy or in other words the muscles shrivel up due to under youth since the motor neurons are damaged by the virus a low muscle tone and muscle twitching which can occur by abnormal firing by some of the neurons that may still be providing innervation to the muscles now you might think wait only half a percent of people face this motor neuron damage and muscle paralysis that seems like such a small number well let's put it into a little bit of perspective if we take a look at a football stadium of about maybe a hundred thousand people here about 90,000 people may be asymptomatic only about 5,000 to 10,000 people will actually have symptoms so maybe this group of people right here and the people that experience muscle weakness maybe all of the members of the band and all the members the players the coaches of both teams will be affected now still this may not seem like a lot in comparison to all the other people who are asymptomatic who aren't feeling any symptoms but the disease can spread very easily from person to person which leads to more and more people being affected by the polio virus so though it's a small amount of people the damage can be very severe in fact we think about maybe the arms and the legs right you're not able to walk or move your arms but what happens if the muscles that are used in respiration in breathing are paralyzed what if these muscles are damaged then patients can no longer breathe on their own so this can be very debilitating and fatal if it affects the respiratory muscles but what other muscles do we not commonly think about well there's also muscles in our throat and our heart is a muscle there's actually nerves that extend from the lower part of the brain it's also known as the brain stem this area has some neurons that control speech as well as the functioning of the heart so we go ahead and take a view of the underside of the brain you can see right here's the brainstem and there's all these nerves that extend from this part of the central nervous system these are known as the cranial nerves so nerves that might be affected are the glossopharyngeal cranial nerves 9 the vagus nerve cranial nerve 10 the accessory nerve cranial nerve 11 and the hypoglossal nerve cranial nerve 12 so these are motor neurons that can be damaged as well so what are some of the symptoms you might see the glossopharyngeal nerve assists in allowing you to swallow so patients may have difficulty swallowing the vagus nerve controls movement of the throat so I wouldn't be able to talk to you right now without the vagus nerve the vagus nerve innervates other parts of the body as well including the muscle known as the heart so a patient who has their cranial nerves affected should have close cardiovascular monitoring their heart should be monitored very carefully and then finally the accessory this controls shoulder movement and the hypoglossal controls tongue movement so you see not only the muscles of the arms and the legs are affected but also some patients can get this bulbar palsy which is the name for this cranial nerve defect so when these cranial nerves are affected so a patient might have difficulty talking difficulty swallowing and have heart problems as well difficulty actually maintaining their their hearts function this cranial nerve paralysis is known as bulbar palsy and both just refers to the brain stem it's the bulb of your brain and palsy means paralysis so there you go nerves from the brainstem are paralyzed bulbar palsy finally after the initial infection and that patient has had some muscle damage years later a patient may get something called post-polio syndrome post-polio syndrome occurs years after the initial infection it's slow and you get progressive muscle wasting so these muscles that may already be weak can get weaker and weaker now the prevalence of this is not entirely clear it doesn't occur to all patients who end up getting the muscle weakness but we do know that some of these patients get this onset of deterioration and dysfunction of the muscles years after the initial infection