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  University of Idaho
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  Psychology Dept.
  University of Idaho
  Design - P&D  CTI

In general, there were a variety of things that the early physicians found.  In early studies what they found was that some patients basically developed progressively weakness.  When they looked at these problems, they found problems with the nerve cell bodies or peripheral nerves, but no problems with the muscle fibers; while other patients had problems with the muscle fibers but had no problems in the nerve cells.  So, two major important features began to occur with the different types of investigations. Physicians found that some neurological disorders only affected sensory systems while others only affected motor systems.  Finally, the neurological problems could only affect one component of the neuron.  For example, it might only affect an axon or a Soma, but not affect the entire nerve cell itself.  So, these are some basic things people began to find.  As a result of these and other studies that came along a little later, we began to identify a variety of movement disorders.  I’ve listed these on slide three.  As you can see, we have several groups, we have nerve-muscle-synapse problems (classic example is myasthenia gravis) which we’ll talk about soon, and we have neurogenic and myopathic diseases like Lou Gerhig’s disease.  We also have brain structure disorders.  So, we might have Parkinson’s syndrome (that is a basal ganglia disorder) or the cerebellum disorder, (such as hypertonia) and others.  So, let’s talk about a few of these and get an idea about what they are and how they work. 

The first disorder that I want to talk about is myasthenia gravis.  Basically myasthenia gravis is a severe weakness of the muscle tissue itself.  It occurs because of a functional disorder that occurs between the motor neuron and the skeletal muscle itself.   There are two major causes of myasthenia gravis.  The first of these is an autoimmune disorder.  That is, the immune system begins to attack the nerve-muscle synapse.  The other cause is through a genetic cause. 

Let’s talk about the autoimmune type first.  This is shown in slide five.  Basically what happens in the autoimmune type of myasthenia gravis is that antibodies are produced that basically attack the Nicotinic ACh. receptor that we’ve talked about earlier.  As a result, it reduces the number of receptor sites and the muscle becomes weakened.  As we can see in slide six, it affects a wide variety of different structures.  It affects the cranial muscles of the face and limb muscles.  So, you might see eyelid and eye muscle problems or weakness in the arms and legs.  Interestingly, the symptoms can vary during the day and between days.  You also can get remission and exacerbation.  So, you get times when you’re doing real well and other times where you are not.

In addition to that, there’s basically no evidence of denervation even though the muscle weakness is occurring.  So, what you’re doing is targeting that muscle synapse.  We can reduce and reverse that weakness by giving drugs that inhibit acetylcholinesterase, which basically breaks down acetylcoline.  So, you put more acetocoline in the synapse site.  As a result, the person has more firings and the muscle is then stimulated.

Some symptoms of myasthenia gravis are shown in slide seven.  Generally, we get muscle fatigue and weakness, and over time, we begin to get a detrimental response of the actual muscle itself.  So, what you see is muscle weakness.  You’re not as strong any more and it’s not a fatigue type of issue.  Over time it continues to become worse and worse. 

Now, as we can see in slide eight, there are several different treatments.  As we talked a little bit earlier about, anticholinesterase inhibitors provides some symptomatic relief.  We can also use plasmapharesis therapies which are used for other types of disorders as well.  Plasmapharesis basically removes plasma.  You then filter out the acetylcholine antibodies.   However, whatever treatment we use, each does not alter the course of the disease, and over time, the disease grows progressively worse. 

There are also other types of treatments and these are shown in slide nine.  One of the classic ones is thymectomy.  Basically what we do is remove the thymus which is extremely important in immune system functioning.  When that occurs, half the patients enter total remission from myasthenia gravis and have no more problems.  You might also see this with other disorders as well. 

Well that’s myasthenia gravis.  There’s also a wide variety of other movement disorders. The next group that I want to discuss is what we call neurogenic and myopathic diseases. This begins in slide 11.  These symptoms appear slower than when a nerve is cut.  When a nerve is cut completely you have instantaneous loss.  In these types of disorders, however, the symptoms begin to occur as the muscle becomes weak and begins to waste away.  In essence what you have is what is called atrophy.  It is going to affect all sorts of things.  You have all sorts of different symptoms including cramps.  The muscle may not be able to relax and you can also get red-tinged urine from the breakdown of the muscle product.  However, it also does not involve sensory neurons.

With neurogenic disorders (as we see in slide 12) you may get just a limb weakness.  You also can get muscle twitches which are good indicators of neurogenic disorders.  Now this isn’t the little muscle twitch you get every once in a while in your arm or your leg or even in your face.  This is going to be occurring for a long, long period of time.  These muscle twitches are what is called fasciculations.  In myopathic disorders you may also get distal weakness as well and a wide variety of other symptoms. 

With the motor neurons, there’s a variety of different things going on.  Remember motor neurons are basically neurons that are coming from the spinal cord of the brain stem, and they’re innervating skeletal muscles.  Premotor neurons are what we call upper motor neurons. These are the neurons that are going to be in your cortex and other major structures.  Usually what they do is they synapse to lower level motor neurons.  Ultimately, the combination of both groups make up the neurons in your spinal cord, and the classic example of that is the corticalspinal track.

So what happens when you have damage with premotor and lower motor neurons?  Well as you can see in slide 14, the diseases from each group are going to produce very specific symptoms.  When you have lower motor neuron disruption, you develop atrophy and fasciculations.  You get decreased muscle tone, loss of tendon reflexes and weakened and what we call wasted or twitching muscles. 

In upper motor neurons, the symptoms are different. You get muscle spasticity and overactive tendon reflexes.  So, when you have something occur with a reflex, you get much more exaggeration of the reflex.  As a result, you get an overactive tendon reflex.

So, what are some disorders that occur with these particular types of disruptions to the premotor and lower motor neuron areas?  Well the first one is what is called Lou Gehrig’s disease or amytrophic lateral sclerosis.  Basically, it involves both lower and premotor neurons it’s characterized by atrophy of the muscle and hardening of the spinal cord due to astrocyte increases.  Basically, what you get is a scarring of the lateral columns in the spinal cord.  In general, the premotor neurons continue to degenerate, and this occurs until the person dies.

Usually this disorder begins around age 60, but can begin much earlier.  It often begins with fine motor difficulties, such as working with tools.  You can’t seem to work as well or even play the piano.  You ultimately develop weakness in the limbs, and you also get an increase in tendon reflexes.  There’s a wide variety of other symptoms that occur as well.

Another major group of disorders that occur in this area are what we call the muscular dystrophies (slide 19).  These are inherited and oftentimes these symptoms begin before even adolescence occurs.  Ultimately, all the symptoms are caused by weakness.  Over time, the weaknesses become more and more severe.

There are lots of different types of muscular dystrophies and I’ve listed several here in slide 20.  Muscular dystrophies are basically characterized by muscle weakness and cause a person to have more and more problems as time goes on. 

So those are two major types of disorders.  Well, what about some upper brain disorders?  Well, the first major type is what I’m going to call the basal ganglia disorders.  There are a wide variety of different types and as we see in slide 22, all of them have tremor or some kind of other involuntary movement as a major characteristic.  In addition to that, you’ll have problems in muscle tone, posture, and slowness of movement.  You also get diminished movement or excessive movement, depending on the particular problem that you have. You may also develop cognitive disorders as well.

 What are some structures that we talk about in the basal ganglia?  Well as we can see, it consists of a variety of different structures (you can review that from an earlier section if you need to do that).  But, the primary thing is that it’s going to be getting information from the motor cortex and the substantia nigra.  As we see in slide 24, there’s a variety of different output sources.  These are going to the motor cortex, and to the basal ganglia loop that contains a variety of different structures.

Well what are some disorders that occur with this structure?  Well, the first of these is what is called Parkinson’s syndrome or Parkinson’s disease (begins on slide 25).  It is basically a hypokinetic disorder and is one of the most common movement disorders.  As we see in slide 26, it has a variety of different symptoms.  Some examples include reductions in spontaneous movement, reduced amplitude and velocity of voluntary movement called bradykinesia.  The classic symptom that you often see with individuals with Parkinson’s is a tremor at rest.  You also see a shuffling gate, flexed over posture, and oftentimes individuals do not have good balance as well.

The classic symptoms (as we see on slide 27) are the tremor at rest and a rigid facial expression.   Basically the cause of Parkinson’s disorder is due to a degeneration of dopamine neurons in the substantia nigra.  This can occur from a wide variety of causes, including environmental causes as well.  The result is that more output goes from the basal ganglia to the thalamus and the cortex.  As a result you are going to get more activity and you get more symptoms.  Remember the basal ganglia is designed to slow things down, help with the movement, and smoothing out the movements. 

What are some treatments for basal ganglia disorders?  Well there’s a wide variety of drugs that we can use.  The classic one is probably one that you have heard of, which is called L-Dopa or Levodopa.  It works for about three to five years and then begins to lose its effectiveness.  There’s also a wide variety of other drugs out there as well.  Each of these drugs has their own effectiveness rates.  In addition, we have also used (as we see in slide 31), tissue implants.  There are a variety of different techniques that one can use.  Each of them have variability in their success rates, but the big one right now (and the most controversial) is what we call fetal tissue implants.  Basically this involves placing dopamine secreting neurons from an unborn fetus into the basal ganglia.  Usually what you do is you remove the nerve cells from the basal ganglia in the aborted fetus, you put them in some kind of petri dish, allow them to incubate and grow a little bit, and then you take that tissue and insert it, usually with a microcanulla  of some sort into the basal ganglia.  The results are mixed.  Some individuals do very, very well with the fetal tissue implant, others do not as well.

There are also some different types of lesions that we can use, we can lesion some structures within the globus pallidus and that will also relieve some symptoms of Parkinson’s disease. 

In addition to Parkinson’s disease, there are other disorders that occur within the basal ganglia.  The next one is called Huntington’s disease and shown in slide 32.  Huntington’s is basically a hyperkinetic disorder.  It’s caused by a hereditary problem on chromosome 4.  ultimately, what occurs is neurodegeneration.  It’s characterized, as we see on slide 33, by a wide variety of different things.  We have behavioral psychiatric disturbances, cognitive impairment, and usually death 15 to 25 years after onset.  The problem with this is that most people who are diagnosed with Huntington’s are diagnosed around age 30 to 50.  Usually these people have already had children before the illness has occurred and as a result these children oftentimes with have Huntington’s as well, and the process continues.  So, it’s extremely important for people who do have Huntington’s to get good genetic screening and good genetic counseling before thinking of having children if they have Huntington’s in their background. 

The symptoms, as we see in slide 34, basically involve excessive motor activity which is involuntary. You also have decreased muscle tone, and you uncontrollable, jerky, limb movement.  So, basically the limbs jerk without any kind of control.  In addition, we also have damage that occurs across the brain.  Often this begins in the striatum and can result in rigidity and akinesia.  We also have damage from Huntington’s in other areas as well.

Well, we’ve talked about basal ganglia disorders.  What are cerebellar disorders?  We talked about earlier about the cerebellum.  Basically, the damage results from damage to the cerebellum itself.  Again, the symptoms are going to depend upon the location of the damage.  There’s a wide variety of different symptoms that one can see.  Some of these are listed in three categories on slide 37; hypertonia, anomalies in movement, and tremor at the end of a particular movement are classic examples. 

Hypertonia (as we see in slide 38) is a reduced resistance to limb displacement.  So, what happens is that when you go to the doctor’s office and they tap your knee with the percussion hammer (the little orange or red hammer shaped like a triangle), to check your reflexes, what happens is you normally reflex and then the knee returns to a kind of resting position.  With hypertonia, the leg reflexes but oscillates several times after it comes back down.  In addition to that, you can also get abnormalities in movement.  The classic example is called ataxia.  Here what you get is a lack of coordination of a movement.  So, you have a delay in getting a response, or you have errors in the rate and irregularity in the movement, or you can’t do some things very well.  The classic example is, you take your hands and put them out palms up, you then tap the palm with one hand, turn it back down and tap it with the other hand, and you continue to repeat that movement over and over.  You cannot do that technique very well with cerebellar types of problems.

You can also have tremor at the end of the movements.  So, the person moves their arm to some location and then tries to stop.  What it does is stop, but it overcompensates and so you get lots and lots of jerks and over-corrections.  So, think about catching a baseball.  You go past the baseball, then you go back the other way, and other way, and other way until it’s right where you’re supposed to catch the baseball.

There are lots of different types of places where you can damage the cerebellum (see slide 41).  Again, the damage is identified based on the type of symptoms.  As we can see here, there’s a wide variety of symptoms that you can observe. With some kind of damage to the vermis, you  have problems in the control of muscles in the trunk.  You often have problems with balance and just standing or sitting still.  You can also have damage in slurring in speech.  The classic symptom is what we call a scanning speech.  Basically what you do is say one word at a time, so you talk like this.

Intermediate cerebellar damage is shown in slide 42.  Damage here causes a lot of different types of problems, but basically what you often see are limb tremors, uncontrolled actions, and often problems with moving more than one joint at a time.

Finally, as you can see in slide 43, we also have other problems that can occur as well in relation to memory and mental problems.  The classic example is procedural memories.  These are memories that we use to perform movements without really thinking about them (such as driving the stick shift of your car, or working on your computer, or riding a bicycle).  With procedural memory damage, you have problems in motor learning.  Also, you cannot recall and do those things very well any more.  Again, with the damage in a particular place, that is where the symptom will be.

So in conclusion, we have lots and lots of types of different types of muscular and motor disorders.  Some can be helped, others can’t.  Sometimes the symptoms are very, very useful in diagnosing brain damage.  It becomes extremely, extremely important for the neurologist, and the neurosurgeon to really accurately identify where those particular problems are occurring  One person that can really help with diagnosis are what we call neuropsychologists who are trained  to give a wide variety of different types of neuropsychological batteries and identify where particular brain problems and brain damage has occurred. 

Well. that concludes this section.  We hope you are studying hard.  So, have a great day.