You may have heard ofParkinson’s disease before. Maybe when you heard ofsomeone raising money for the Michael J. Fox Foundation, or maybe you’ve listened to Muhammad Ali speaking about the disease. Both of these guys actuallyhave Parkinson’s disease, and they’ve done a really good job at raising money for, andawareness of, the disease. But what exactly is Parkinson’s disease? Parkinson’s disease is a progressive neurodegenerative disease. We call it a progressive disease because it progresses. It worsens over time. We say that it’s aneurodegenerative disease because during the disease there’s actually a loss, a degeneration, of neurons in the brain. In Parkinson’s disease, we actually see a loss of a particular kind of neuron, and these neurons arecalled dopamine neurons. Dopamine neurons make alittle signalling chemical called dopamine, which is really important for allowing us to make normal movements. A lot of these dopamine neurons live in an area of the braincalled the substantia nigra. The substantia nigra we can see here. It sits here in the brain,above the spinal cord, in the part of the braincalled the midbrain. When these neurons arelost, there’s a reduction in the amount of dopamine in the brain. Again, that’s because these neurons, they’re used to make a lot of our dopamine and now they’re not here anymore. And this is the really important part, because when there’s thisreduction in dopamine that’s when we start to see the main movement signsof Parkinson’s disease.
Let’s talk about these signs. One of these signs is shakiness, which can often be inthe form of a tremor, maybe in the hand or the finger. A second sign is stiffness. That stiffness is felt when the person bends part of their body. Maybe the arm or the leg or the wrist. When they’re bending that body part, let’s say it’s the arm, the movement just isn’t very smooth. It doesn’t feel very fluid anymore. Instead it actually feels really rigid. A third sign is slowed-down movements. This happens because itactually takes the person longer to complete a movement. A good way to think about this is to imagine the lasttime you were in water. Maybe you went to the pool, or you went to the beachto go swim in the ocean. You can probably remember trying to do a somersault underwater, or maybe running away from your friends. If you think back, you can remember that it actually took you a lot longer to do these things in water than it would have if you were on land. That’s kind of what it’s like for someone with theseslowed-down movements. They can do them. It just takes a lot longerfor them to do them.
The fourth main sign isproblems with balance. Feeling really unsteady,or really unstable when standing or walking around. Now, not all patientswith Parkinson’s disease will have all of these problems, but most will have them at some point during the course of the disease. Now, this last one that we talked about, the problems with balance, that usually crops up later on, once the person has had the disease for quite a few years. It’s actually these firstthree that are normally used to decide whether or notsomeone has Parkinson’s disease. All these main movement signs together actually form a symptom complex called Parkinsonism, or Parkinsonian syndrome. That means that Parkinson’sis actually a disease that causes Parkinsonism. There are a few otherneurodegenerative diseases that can cause Parkinsonism, this symptom complexthat we’re talking about. But Parkinson’s diseaseis the most common, so because of this, weoften call Parkinsonism caused by Parkinson’sdisease Primary Parkinsonism, and then we often called Parkinsonism caused by other neurodegenerative diseases Secondary Parkinsonism. Now, Parkinson’s diseasedoesn’t just cause Parkinsonism. Remember that this isa disease of the brain, and when things break down in our brain, our master control center, there’s often more than one kind of symptom. People with Parkinson’sdisease can also experience psychiatric problems such as depression, cognitive problems such as memory loss and trouble with concentration, and lots of other non-movement symptoms. This can include problemswith their sense of smell and problems with their sleeping patterns.
The causes of Parkinson’s disease are actually largely not known. For the majority of cases, we actually don’t knowwhat triggered the disease, so we call these cases ideopathic. “Ideopathic” meaning thatthe cause is unknown. While in the vast majority of cases there is no family history of the disease, about 15% of people actuallydo have a family history and for these people their Parkinson’s appears to be caused by a mutation in one of a few different genes. Depending on which gene is the culprit, a mutation can eithercause Parkinson’s disease or it can increase a person’s chance of getting Parkinson’s disease. If someone has a problemwith one of the genes that can actually cause the disease they’ll definitely developit, but if they have a problem with one of the genes that can increase the chance of getting Parkinson’s disease, they may or may not develop the disease, but they are more likely to than someone who doesn’thave the mutated gene. Genetics are the culprit once in a while, but again, most of the time, we don’t know what causedParkinson’s disease. Despite this, there are some risk factors associated with developing the disease. A risk factor is something that increases your chances of developing a disease. You could say that havinga certain gene mutation is a major risk factor for Parkinson’s, but there are some othernon-genetic risk factors as well. For example, exposureto certain pesticides and some cleaning chemicals. Older age, so once youget to about 60 years old your risk of developingParkinson’s disease increases and it continues to go upwith each passing year. So as well we have ahistory of concussions as a risk factor of Parkinson’s disease, and gender. For some reason, we’renot entirely sure yet, men are a bit more likely than women to develop the disease. Another risk factor isregularly breathing in heavy metal particles like copper or manganese or lead.
Maybe if you’ve livedin an industrial area where those might be found in the air. Again, these are risk factorsfor Parkinson’s disease, which means that they’re associated with a higher chance of developing the disease. The treatment of Parkinson’s disease will normally involve medication to help deal with the movement symptoms, and to do that, the way thatmany of these medications work is by replacing or increasingdopamine levels in the brain because remember, ourdopamine-producing neurons have degenerated during the disease, and for some patients, themedication works great. It may be all that they needto minimize the symptoms. But for most patients, afterthey’ve had the disease for several years, their medication just doesn’t really cut it anymore, so when this happens,they may have surgery to help deal with their symptoms, and the goal of surgery is to inactivate areas in the brain that are causing their movement problems,like that shakiness or stiffness that we talked about earlier. This brings us to the long-term outlook for someone with Parkinson’s disease. Unfortunately, Parkinson’sdisease is a progressive disease so the disease will continue to develop over the years after diagnosis is made. While none of our current methods are able to stop the disease, medication and surgerycan be really helpful for managing the symptoms, and making sure the personwith Parkinson’s disease has a high quality of lifefor as long as possible.
I just want to mentiona common misconception that can crop up when we hearabout Parkinson’s disease, which is that Parkinson’s disease only occurs in older people. While it is true that theaverage age of diagnosis is around 60 to 65, about five to 10 percent of patients are diagnosed before the age of 50. This is often referred to as young or early onset Parkinson’s disease. For patients with youngParkinson’s disease, those gene mutationswe talked about earlier seem to be the cause more often than they are for patients diagnosed in the average 60 to 65 year-old range.