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What is cerebral palsy and what causes it?

Video transcript

cerebral palsy is actually an umbrella term that we use to describe a group of disorders that affect a person's ability to move in a normal way and cerebral palsy occurs because of damage to the developing brain may be caused by an infection or loss of oxygen for some reason and this damage it usually occurs during early development anywhere from in utero to about toddlerhood so while the brain is still undergoing really critical development so this damage it occurs in parts of the brain that control our movements and this damage it is permanent but it's not progressive so the initial damage to the brain it doesn't worsen over time but the problems with movement do persist for the affected person's entire life so now that we know a little bit more about cerebral palsy we can make a bit more sense of the name so cerebral means brain so this is where the damage is and palsy means muscle weakness or loss of function so this is describing the main problem that arises from this damage in the brain so let's highlight the general parts of the brain here that are involved in movement so these will typically be the areas that get damaged to cause cerebral palsy so we've got the cerebellum and the motor cortex these are the two bits that we can see if we look at the brain from the outside and then if we go a little bit deeper inside the core of the brain we've got the basal ganglia so these three parts of our brain we can think of them as our movement centers and what they're involved in are things like helping us make movements so they help us coordinate and move our arms and our legs and our torsos but they also help us do things like maintain our balance and control our posture our muscle tone and our reflexes so it kind of follows that when these movement centers themselves or the tracks of neurons that they use to communicate with each other and with our muscles when any of these components are damaged during development the person will develop problems with their movements and that's what we call cerebral palsy so one of the interesting issues with cerebral palsy is that the amount of trouble that each person has with their movements can vary a lot between different people so let's explore this a little bit further let's draw a severity spectrum here for cerebral palsy so the further the right we go the more trouble the person has with their movements so on our left here on the mild end of our spectrum we'll have people who aren't too badly affected from a sort of functional day-to-day point of view so this little boy here it looks like he's able to walk and run around pretty well and we know that cerebral palsy can cause trouble with posture and balance and coordination so because this boy is able to run around like this we would say that he's not too severely affected his form of cerebral palsy is quite mild he'll still have some movement problems maybe he can't run quite as fast as someone without cerebral palsy or maybe he has some trouble with coordination so maybe something like running and throwing a ball at the same time but overall he's able to function pretty well on a day-to-day basis but if we head over here to the severe end of our spectrum the picture looks quite different so this girl here also has cerebral palsy but instead of being able to run around she needs to be in a wheelchair and it looks like she's having trouble with her posture so she needs to be held upright and you know her cerebral palsy is so severe that she can't really get around by herself in her chair it looks like she needs someone to operate it for her so let's actually re label the ends of our spectrum here so that we're painting a better picture of how wide this range of movement problems really is in cerebral palsy so let's say that the severity spectrum for cerebral palsy goes from running to wheelchair and everything in between so this gives us a pretty good idea of how wide that range of movement problems can be so what we're actually looking at here is something called the gross motor function classification system or the gmfcs and each of these pictures here actually represents the different levels of the gmfcs so this system is a really useful way for characterizing the severity of someone's cerebral palsy it gives us a good fairly standard way to get an idea of a person's movement abilities or their movement impairments so let's leave this for a moment and go back to those damaging events that I mentioned the events that damage the movement centers during development and cause cerebral palsy so let's make another spectrum here and this time we'll make a spectrum of causes and we'll make this spectrum a little different let's go from nature on this end to nurture on this end and nature refers to things that were born with right things that are innate like our genes or our chromosomes and by nurture we're referring to our environment after we're born so all of our personal and actually different causes of cerebral palsy can happen at different periods of early development so let's do some color coding as well so anything that I write on this spectrum in blue that's happening before birth so prenatally and anything that I read in green that's going to be happening during the birth process so perinatal E and anything in this nice salmon color here can be for things that happen after birth up to the first few years of life so postnatally alright so let's start with events that it can occur before birth so in utero so all the way over on the nature end of our spectrum we can put genetics so there are a few genetic causes of cerebral palsy so mom or a dad maybe they inadvertently passed on a mutated gene that results in damage to one of these movement centers in the brain but these are pretty rare causes of cerebral palsy so the rest of the prenatal events that can cause cerebral palsy kind of fall in between nature and nurture they happen before birth they are prenatal causes but they have a bit more to do with the environment that the fetus is in so we'll put these prenatal events around here on our spectrum of causes so the first event that will pop down here is infections infections that the fetus gets from mom so congenital infections and one group of congenital infections that can cause cerebral palsy is a group referred to as the torch infections and torch is a mnemonic for toxoplasmosis rubella cytomegalovirus and herpes simplex virus and there are actually two types of herpes simplex virus type one and two so we'll put both of these down here and I love this one for last on purpose because it's kind of a catch-all so the O stands for other just kind of because we had to make the pneumonic fit somehow but we can put other infections down here like syphilis in this group because even though they don't really start with any of these letters it can still cause cerebral palsy so other things that can go wrong in the prenatal period well we can run into some problems with the placenta so if we check out our developing fetus here here's the placenta and here's the umbilical cord so these two are what allow the fetus to get oxygen and nutrient rich blood for mom so sometimes the placenta it doesn't form properly or it can be damaged during gestation and when this happens the placenta can't really do its job of delivering oxygen and all of those important nutrients to the fetus which the fetus really counts on to develop properly so we call this placental insufficiency and this is another possible cause of cerebral palsy and one other thing that we'll put down here in our prenatal period is prematurity so this is when a baby is born early defined as before 37 weeks of development in utero and just to put that in some context a baby that's born on time and we call these babies term babies they're born around the 40 week mark and one of the main reasons that we're putting down prematurity here on our causes spectrum is because the brains of premature babies can be really fragile and susceptible to damage and there's actually a particular kind of brain damage that premature babies are at risk for that can cause cerebral palsy and this is called periventricular leukomalacia or PVL for short so periventricular means around the brain ventricles which play a part in keeping our brain nourished and Luco which means white refers to the white matter in the brain so PVL is a type of brain injury of the white matter of the brain that lives around the ventricles and it turns out that the vast majority of babies with PVL end up developing cerebral palsy because these periventricular areas they contain some really important tracts of neurons that are involved in controlling our movements so prematurity puts a baby at risk for developing pvl and PVL often causes cerebral palsy so maybe we'll put pvl here in brackets beside prematurity just so that we remember one of the main reasons that we're putting prematurity down here on our causes spectrum so what about the perinatal period what sort of events can occur during the birth process and cause cerebral palsy well if mom has one of those torch infections instead of the fetus getting it during pregnancy mom might actually pass on one of these infections to her baby during the birth process as the baby is coming out of the birth canal so we can put torch infections down here again this time is a perinatal cause of cerebral palsy and you can see that we're trending down our spectrum a bit progressively to the right towards the nurture end and that's because we're kind of getting into the realm of nurture we're moving more towards those environmental causes that happen after birth so the second perinatal event that we can put down here is oxygen deprivation or birth asphyxia and this happens when something gets in the way of the baby's ability to breathe so for example if the umbilical cord gets caught around the babies neck wall is being delivered so we actually used to think that this lack of oxygen because of complications at birth like problems with the umbilical cord was the cause of cerebral palsy but now we know that this type of event only accounts for a handful of cases of cerebral palsy less than about 10% and that the majority of things that go wrong and cause cerebral palsy actually happened during the prenatal period so now let's go on and look at events that can happen during the postnatal period and remember here we're referring to the period after birth up until the first few years of age and now we can jump all the way over here to the nurture end of our spectrum of causes so here we've got things like head trauma so maybe the baby's brain was damaged during a car accident or maybe they had a near drowning experience and that deprived them of oxygen and in this damaged the brain because remember that our brain tissues really rely on oxygen in order to stay nice and healthy and on that note we can put down stroke as another cause this is another event that reduces oxygen flow to the brain which can damage those developing movement centers and it's really important to note that strokes don't just happen in elderly people they can happen in infants too and they can cause cerebral palsy and let's make our last example infections and the major cerebral palsy causing infection we can see postnatally is actually not a torch infection it's bacterial meningitis so this is when the meninges the protective coverings that we have around our brain in our spinal cord when these become infected so in meningitis you get this really large inflammatory reaction around these parts of the brain there's essentially a war going on between our immune system and the meningitis causing bacteria and if you've ever seen any war movies or taking any history classes just imagine what the battlefield looks like when the war is over or even while it's still raging it's pretty damaged and unfortunately in meningitis our brain is the battlefield and and can thus become quite damaged so if this battle goes on around any of the movement areas then we can end up with cerebral palsy and by the way I should clarify that these damaging events they can cause cerebral palsy but they won't cause it every time that they happen so in other words it's totally possible for someone to have one of these events occur and not develop cerebral palsy