Nervous System Diseases and Their Anatomy

This week we focused on diseases and disorders of the nervous system.  One lead-in to this unit was our homework assignment, which was to do an online virtual brain surgery for treating Parkinson's Disease.  All of us who did the simulation enjoyed it a lot.  Basically, the operation involves the implantation of electrodes into the brain areas that are damaged in Parkinson's Disease.  As I explained to the students, the neurons in that area die and never grow back.  We don't understand exactly how those neurons function, but stimulating that area electrically is very helpful for reducing and sometimes eliminating many of the symptoms of the disease.

During the game, you first see the patient with her symptoms, which are that her hands shake (the "tremor" that is typical of this disease).  Next, you go through all the steps of the procedure: inserting screws called fiducials into the skull, using them to precisely map the path for the electrodes to follow, drilling into the skull and placing the equipment for guiding the electrodes, slowly and carefully pushing the electrodes into position, waking the patient to use their reported sensations to show whether they have been placed correctly, closing up and removing the equipment, then two weeks later testing for the correct power, placing the batteries into the chest region and connecting them to the electrodes.  Another more complete explanation is here.  It was detailed and fascinating to actually do the simulated surgeries!

After discussing the simulation and why we did it, we moved on to an active discussion of nervous system diseases and disorders.  There are a huge number of problems that happen with the nervous system, and I fully admitted that I am not an expert on all of them, or even very many of them.  I have studied a few nervous system diseases in depth, which we discussed, but most of what we are talking about are diseases that I know a fair number of basic details about.

I brought in two brain models that I borrowed from the UW Neuroscience Training Program.  One was a rather large, colorful brain model labeled with each region's function.  We didn't spend a lot of time on it, but it is very helpful for seeing exactly where the regions we are discussing are located.  It also illustrates the mapping of the body parts onto the motor area (where the neurons are that tell that body part to move) and the sensory area (where the neurons are that tell us we are sensing touch at that body part).  It comes apart into four parts, so you can see some inside brain regions too, but we couldn't find the substantia nigra (area first affected in Parkinson's Disease).

The other model was specifically designed to illustrate a number of fairly common nervous system diseases.  Unfortunately, it was missing the informational card that would confirm for sure which parts of the model were supposed to illustrate what, and also there was a piece of brain blood vessels that was missing.  The diseases modeled were: 

• alcoholism
• Alzheimer’s disease
• aneurysm
• depression related tumor
• seizure related tumor
• migraine
• multiple sclerosis
• Parkinson’s disease
• stroke
• subdural hematoma

We only had time to discuss some of these diseases.  For each disease, we got up out of our seats and made a respectful effort to act out the symptoms of the disease.  This was to solidify what we discussed, get a feel for what it might be like to suffer from the disease, and of course to stay active.  Here's what we actually discussed:

• Parkinson's diease begins with the loss of neurons in the substantia nigra, and the model showed us two substantia nigras:  one looks like a little, blackish, half mustache, and the other was blank.  The blank one had lost over 90% of the neurons that had been there, and showed what that area looks like in a Parkinson's disease patient.  Normally, there are I think at least a million neurons in the substantia nigra on each side.
• Alzheimer's disease is a progressive disease that first and most deeply affects the memory.  It is a disease that involves dementia, or a specific type of memory loss.  Dementia is a general term for the type of memory loss in which the patient has severe enough problems with thinking, memory, and reasoning that is severe enough to interfere with daily functioning.  Sometimes the person will forget people they've known for a long time or forget what they're doing.  

• I once cared for a woman with advanced Alzheimer's disease for an evening, and it was very interesting and sad to see firsthand the effects of the disease.  This woman told the same brief story over and over again, seeming not to know that she had told the same story just a few minutes before.  She had been retired for years, but forgot that and had a hard time believing me when I told her that she didn't need to go to work.  Her apartment door needed to be locked to prevent her from wandering out and getting lost.  
• As you can see in the picture to the right, many areas of the brain get much smaller in advanced Alzheimer's disease.  Vision and motor areas are not badly affected, and patients don't have a lot of problems with movement or sight, but memory areas are destroyed, olfactory areas (sense of smell) are damaged, and the frontal lobe of the brain, which helps us think ahead and plan, is severely affected.
• Aneurysm is when a blood vessel in the brain has a weak spot that then fills up like a balloon.  Eventually, it can leak and/or rupture, and this is a major problem.  Doctors can do surgery to fix the area by clipping the aneurysm.  If they do this in time, the patient is fine, but if the aneurysm ruptures, there is generally no way to save the patient and he or she dies.
• A friend of my had an aneurysm that started to leak and might have ruptured if it hadn't been
  
  caught in time.  Her symptom was a severe headache like she never felt before, and luckily she was right across the street from Duke University Medical Center when it happened (one of the best hospitals in the country, #8 on US News & World Report).  They gave her top notch care, including a relatively new procedure involving raising the patient's blood pressure to prevent the brains blood vessels from closing.  When this happened, I immediately did research to better understand aneurysm and learned that if the patient survives the aneurysm by getting it surgically fixed before it ruptures, blood that leaks from the aneurysm causes a reaction over the next few weeks in which blood vessels can close up.  If that happens, it is almost like a stroke because that part of the brain stops getting blood and oxygen, which can cause permanent damage.  Fortunately, my friend was able to fully recover with no permanent damage, which was at least partly due to excellent care at Duke!
• Stroke is when a blood clot gets stuck in the brain and causes a small or large part of the brain to be without blood and oxygen for a period of time.  There are blood vessels all over the brain, and where the clot gets stuck determines what part of the brain is damaged and therefore what the patient's
  
  symptoms are.  If the speech area is affected, the person may not be able to talk.  If the area relates to memory, they may have memory loss.  Often many areas are affected, and the person may have some paralysis, some speech problems, and some memory loss.  
• There's an interesting book called My Stroke of Insight, which is written by a neuroscientist who had a major stroke. She survived and recovered, and was able to describe what it was like.  It was so severe that she lost her understanding of what numbers were and what a phone was for, and so even though she was near a phone, she couldn't figure out how to call someone for help!  Luckily, someone called her, and hearing her speech get weird, they knew she needed help and got her to the hospital right away.
• Migraine is a special type of headache that is very severe and is thought to be related to dilation of blood vessels in and around the brain.  For some people, there is an aura, which is usually a visual phenomenon like flashes of light a few minutes before the migraine hits.  
• Brain tumors are cancer cells in the brain.  Cancer cells grow and divide without properly obeying the normal signals to stop growing.  Some brain tumors invade healthy tissue and damage it, while some stay separate from the healthy tissue but push into it and cause brain damage due to the pressure.