Neurology Terms
What are the "lower levels of consciousness"?
There are different kinds of levels of consciousness. So you can be sleepy. You can be lethargic, which would make you less lively. There's stupor, which means that you are essentially non-responsive. You can make sounds and moan, but you're not going to say anything. Then finally, you are in coma, where you are not arousable. These are all lower levels of consciousness.
What is a person's "reflex action"?
If I were to tap your knee you would get a reflex action. When I tap the knee and your leg moves, it is because you tell your spinal cord that your knee has been tapped. So if you tap the knee, an impulse goes into the spinal cord, but it doesn't necessarily have to go up to the brain. It goes directly to the motor neuron, and the leg moves. There are diseases which will interfere with that. If the peripheral nerve is involved, your spinal cord may not know that you have been tapped, so the leg doesn't move. If the motor neuron has been damaged or the peripheral nerve has been damaged where the motor fiber is involved, it won't move either. So that is a reflex action. Although there is control over that, some people's reflexes are very brisk and some people's are not, that's from the brain and central nervous system, that's from up above. Movement - if you burn your hand and you pull it away, you don't need your brain, so that's being done on a spinal cord level. That's not going up very high. The fact that it hurts is going up high, but you could burn yourself and it could be a second or two before you realize you've hurt yourself, but you would have moved your hand before that. That would be the reflex.
What is "vertigo"?
Vertigo is a phenomenon that occurs where a patient feels like they are spinning or the room is spinning. But it is their connection with Mother Earth. This is all due to the vestibular system, which is essentially your balancing system. The peripheral part of that is in your ear. That's the labyrinth. The central part of it is in your brain stem. It is a closed circuit. So any part of that, if it is interrupted, will give you a feeling of dizziness and light-headedness. All dizziness, all light-headedness, all vertigo is vestibular. It maybe for other reasons. For instance, if you have decreased cardiac output, because you have some irregular rhythm, your vestibular system may not be getting enough blood, so you'll be light-headed. If you interrupt that, and the most common reason for that is an infection, an injury to your head could do it. But usually it's a viral infection of some sort. As you get older, it could be blood vessel changes, you could have arterial sclerosis or high blood pressure, those can produce vertigo. There is a vertigo that occurs after that, because don't forget, it starts in the labyrinth and then it goes into the brain. So you could have it in your brain. So, for instance, vertigo in an MS patient is due to it occurring in the brain, not in the labyrinth. If you have a stroke in that area, it's going to be in the brain. The symptoms are the same, the one big difference is most of the time, when it's peripheral, you have a positional component to it. So, if you move your head a certain way you get dizzy or you get vertigo. If you look under the bed, you get dizzy, or you get vertigo. If you stand up quickly, you're going to get it. That can occur with central vertigo, but it's less likely. So, one of the things we want to know when a person has vertigo is, is it positional. If they lie still, are they still having vertigo? And if they don't have it, it's probably going to be peripheral. About 90% or 95% of all vertigo is from the ear.
What is a "concussion"?
A brain concussion is when you have a head injury, usually closed, in which you have jolted the neurons, essentially. Very often there is micro hemorrhages around areas of the brain where it's happened. A concussion, clinically, is that you momentarily lost awareness. Now, seeing stars from a concussion. So you don't have to be unconscious. But you should have some alteration of mental state. Most commonplace is when a prize fighter gets knocked down. He gets hemorrhages in his brain.
What is a brain "hemorrhage"?
A brain haemorrhage is where a blood vessel is broken and blood comes out into the brain. Now, there are different kinds of haemorrhages. There are small haemorrhages that occur like in concussion where they're really capillaries that are broken; it's the shearing of the capillary. There are haemorrhages from smaller vessels which might be from a hemorrhagic stroke. Or, there's a big haemorrhage. High blood pressure patients get a large pressure, the wall breaks down, and there's a big haemorrhage that occurs. Those haemorrhages occur, usually, in specific regions of the brain. That's probably the most common. Then there's traumatic haemorrhage which means you get hit in the head or in an automobile accident and you have a haemorrhage in your brain because of the fact that you not only had the contusions that occurred, but you've actually sheared off a vessel. It's blood in the brain, and when you rupture an aneurism that's blood in your brain it could go on the surface of your brain which means the blood vessel is going to go into spasm, or it can go into the ventricle, or it can go into the brain itself and produce a huge mass. When it goes into the brain it produces increased pressure in the brain, as well.
What is a "berry aneurysm"?
A berry aneurysm is where two vessels meet and there is a weakening in the wall which begins to pouch out. If it gets big enough or weak enough, it will burst, and there will be a hemorrhage. There are aneurysms in places other than the nervous system, but brain aneurysms are the most dangerous because of the fact that about 50% of the people who have eruption aneurysm, will die from that, either immediately, or in course. Because of better imaging, we are now beginning to give diagnosis of those aneurysms before they erupt, so if I did an MRI of you, and you had three or four of these, but they were one or two millimeters, they would not be about to erupt. But if they were five millimeters, or a centimeter, you'd have to go and get rid of them before they erupted. And then you'd have 100% survival, because they never bleed and they never give you problems.
What is a "traumatic aneurysm"?
You can get a traumatic aneurysm. So, for instance, if you get a gunshot wound. It damages that vessel, it makes the wall weak, and over time the beating against that weak spot begins to balloon out, and eventually it ruptures.
What is a "coma"?
In general anesthesia you are in a coma. Now, when you're in a coma you could have a normal brain activity, except that it is suppressed because you're essentially sleeping. You will not respond to deep pain when you're in a coma. You may still maintain your blood pressure, you may still be able to breathe. But your brain is essentially asleep, it's not going to respond. it can be reversible obviously, depends on the cause of it.
How long can a person be in a coma?
It depends on the cause of it. So for instance, if you go into a coma because you have renal failure, and then you get dialyzed, you may come out of it within 24 to 48 hours after that. If you have a toxic overdose--if you've taken too much of some medicine or you've made a suicide attempt--as soon as that drug is out of your system, you may wake up from it, providing that you didn't stop breathing or have a cardiac arrest from all of this. If there is permanent damage, even if it's going to be transient, it may take you weeks to come out of a coma. Head injuries, it may take you weeks to come out of a coma. Now, a lot of patients, when they go into a coma from a head injury, after several weeks they will respond to deep pain. They're just not awake, they're not talking, but they may respond to some stimulus. But how long somebody is in a coma is variable. Generally speaking, before we say that somebody is irreversible, we like to have other evidence of brain damage, not just the level of consciousness.
What is "persistent vegetative state"?
We have about ten thousand people in this country each day who are in what we call persistent vegetative state, which means their eyes are open but they don't have any input. This would be the Terri Schiavo type of thing. They have significant brain damage, they may be breathing on their own, they may have a normal heart, but overall, their brain is nonfunctional and it will never be functional. They are being kept alive by machinery and after a while they are on their own. That is what we call persistent vegetative state, and there's a lot of argument about it, but there's absolutely no evidence that those people can receive messages or give messages. After you've been in a coma for about four to six weeks, your eyes are open for the most part, they don't see, but they're open.
What is "brain death"?
It's a legal term. What it means is that the patient is on a ventilator, usually, and who is continuing to have a heartbeat, but you are breathing for that patient as the patient cannot breathe on their own. This is because your brain shows no electrical activity. The temperature is normal because if you put people in low temperature situation, you can suppress brain activity. So you have to make sure that their brain activity is normal. They have no evidence of any reflexes, so they're not maintaining their blood pressure, they're not maintaining their pulse, their temperature has been made normal, and they have no evidence of brain activity by brainwave or by any other study. That would be brain death.