Join Dr. Snell as he reviews shunts and the treatment of Hydrocephalus. This course will be an overview with a focus on brain injury and stroke and educate medical professionals to be able to identify the physical symptoms that are associated with Hydrocephalus, including normal pressure Hydrocephalus. He will also cover potential risks, considerations, and post operative instructions associated with shunt and craniectomy procedures.
Speakers: Tim Benak, Dr. Snell
Video Transcription
Introduction
Tim Benak – 00:00
Good morning, everyone. Thank you for joining us today. We’re going to be presenting on the treatment of hydrocephalus today with Dr. Snell. Dr. Snell how long you’ve been here at QLI?
Dr. Snell – 00:25
Yeah, today actually is the half year anniversary. So I’ve been here exactly 21 and a half years as of today.
Dr. Snell – 00:34
I came here as an intern in 1998, and was just fortunate enough that I was offered me a position. I’ve never had to leave.
How QLI Treats Hydrocephalus
Tim Benak – 00:57
Director of Psychology services is your title.
Dr. Snell – 01:05
Yeah, Director of neuro psychology and psychology service. We’ve got four doctoral level providers, our focus is on from a neuro psychology standpoint, doing assessment says folks come in doing that initial look at their cognitive functioning and helping provide that information for the team for the purposes of treatment planning. Being able to be a consultant to our various team members, when folks that have questions being able to provide education for our clients for their families.
We have psychologists that focus primarily on providing emotional support for our residents and for their family members in education as well. One of our psychologists is getting much more involved in our telehealth services also. So just a variety of different aspects. One of our staff members is very much focused on research applications within the facility and throughout our program. So just a variety of different things that were involved with.
Dr. Snell – 02:33
The topic today, treatment of hydrocephalus, I’m going to talk about primarily shunts because from the standpoint of the treatment of hydrocephalus, that is pretty much the primary mode of treatment.
Options for Treating Hydrocephalus
There are not a lot of options when it comes to treating hydrocephalus. It is something that we frequently see with the injuries, the severity of injuries of the population that we tend to work with.
We don’t have a primary pediatric service. And so as we talk about this a little bit hydrocephalus is something that is often associated with children, particularly with infancy.
From a standpoint of the neurological aspects involved, it is relatively common with the population of individuals who’ve had very severe traumatic brain injuries. It is a little bit less common but does occur when individuals have had intracerebral hemorrhages or strokes. It is also something that as we’ll talk about is a little bit more common with an aging population as well. We’ll talk about why that is.
What is Hydrocephalus?
Basically hydrocephalus is an abnormal accumulation of cerebral spinal fluid within the brain. It can also be an imbalance basically the difference between the production and reabsorption. So this is a fluid that your body is constantly producing, and re absorbing. It serves many intricate functions within the brain.
The problem develops when the enlargement of the ventricular system is a result of that increased pressure. In other words, the fluid within the ventricles begins to push outward, like a balloon being blown up deep inside the brain. And again, as an adult, you’ve got this nice rigid bone helmet that you carry your brain around in that we call the skull.
That becomes a problem when you have increased pressure inside there’s really no way of relieving that pressure. If that pressure is a result of an increased fluid collection, the response is to get some of that fluid out and chunks or ways by which that is done.
Cerebral Spinal Fluid
From the standpoint of hydrocephalus, I want to first go into why we got this fluid inside of our head. Where does it come from to begin with.
So, cerebral spinal fluid is produced deep within the brain. It’s primarily within the tissue that lines the lateral ventricles, the third ventricle and the fourth ventricle. There is a tissue in there called the choroid plexus that is made up of very specialized cells that separates from our blood plasma clear fluid, we call it cerebral spinal fluid.
That fluid is formed through a tissue called the choroid plexus. Now, that is a lining of the ventricles that produces cerebral spinal fluid. It’s a network really of capillaries and very specialized, dependable cells that are found within the lining of the ventricles and dependable cells are one that you’ve probably heard of, glial cells.
There are many different types four major types of glial cells and these are considered support cells within the brain, we’ve got neurons that make up about 10% of the brain’s mass, and the rest of the brain is primarily those glial cells. So astrocytes aglia dendro sites.
These dependable cells are a type of neural glial cell, they line the ventricles, they also line the central canal of the spinal cord. They serve a couple of different purposes, one being the production of the cerebral spinal fluid, another, being a part of what you probably are familiar with a the blood brain barrier.
This forms the equivalent of a blood brain barrier, but for cerebral spinal fluid, so it forms that toxin barrier between our central nervous system and our cerebral spinal fluid.
Cerebral Spinal Fluid Production
Now, you daily produce about 300 to 500 milliliters for us Americans, that’s about 10 to 17, fluid ounces of cerebral spinal fluid per day. And as you can see, within this animation, that little white dot there would be new cerebral spinal fluid that is being produced, and then that is one of the passageways that it flows out.
You have a left and a right ventricle that both feed through very narrow passageways called cerebral aqueducts, into the third ventricle, that would be the one that is most central within that graphic representation. Then it flows further down into the fourth ventricle, which is right around the cerebellum.
Then from there, it flows out and around and both surrounds the spinal column and surrounds the brain. Now, generally, you only have about four to five fluid ounces 125 to 150 milliliters of volume of cerebral spinal fluid within your body at any given time. So what that means is your body produces much more of this than your body typically contains.
Cerebral Spinal Fluid Turnover
It turns over, the rate of production and reabsorption means that about every seven and a half hours, you have replaced all the cerebral spinal fluid in your body. Now part of that turnover has to do with one of the functions of cerebral spinal fluid that we’ll talk about in just a moment, which is clearing waste products.
So it constantly needs to have a fresh clean supply, so that it can help clear waste products from deep within the brain. A much more detailed graphic, this is a really detailed set production and reabsorption.
So if you see some of those arachnoid villi that are around the outer layers, kind of marked very up at the top with the number eight in a very tiny circle, not sure if you can make that out but it lines the kind of the inside of the skull, just inside that is the lining that covers the brain and that’s where these reabsorbs and channels are primarily located.
And as you can see within this graphic, as well for cerebral spinal fluid is is represented by these different colors of blue. It does completely encompass and surround brain tissue.
So it is a fluid that is contained both within as well as around the brain. The brain itself tends to weigh about, I think it’s 1300 grams or so, it’s about three pounds all together. In order to maintain its shape since it is very much like, not quite done jello in its consistency in order to help maintain its shape, this cerebral spinal fluid basically floats this jello away from the surfaces of the inside of your skull. It provides a buoyant force from the standpoint of being able to put it in water and surround it with a little bit of a cushion.
Protecting Your Brain
Your brain, for lack of a better word floats inside of your skull in the cerebral spinal fluid. It provides some degree of protection from sudden movement, so sudden acceleration or deceleration means that every time you, bump your head, you don’t necessarily impact your brain on the inside of your skull.
So that cushioning protection, that that bubble wrap around our brain is our cerebral spinal fluid, which is both produced deep within it, and as I said, flows around it.
Now, because it flows around your brain, and if you’ll notice, at the very bottom of that graphic around the spinal column, it also helps protect the spinal column, it provides a little bit of cushioning there. If you want to do a chemical essay of what you have in your cerebral spinal fluid, for example, you think that there’s an infection within the brain and you want to look at the waste products that are being circulated away from the brain, you would draw off a little cerebral spinal fluid, and you would do your chemical testing on that.
Accessing Cerebral Spinal Fluid
Now, it is much easier to pass a needle through the disc or through these spinal column around the lumbar region where you have somebody bend over and do that lumbar puncture between the vertebra. It is much easier to access a fluid there than it is to mechanically drill a hole through a bone such as your skull to access that fluid.
It is a way of getting to that cerebral spinal fluid, if you need to look and see chemically what’s going on inside the brain, because it circulates within the same field. That’s an easier way of doing that.
Other Functions of Cerebral Spinal Fluid
Now other aspects of the function of cerebral spinal fluid, including acting as a cushion or a shock absorber, also kind of like the waterways of our planet, these fluids flow, they can help channel and clear waste products from our central nervous system.
When our brain is functioning normally it is constantly producing byproducts. These byproducts are from energy production from normal cellular waste products. This fluid is a means by which those waste products are efficiently cleared away from brain tissue.
Intracranial pressures can also be regulated by normally flowing and functioning cerebral spinal fluid production and distribution. So to some degree, our cerebral spinal fluid and the volume of it within the brain can accommodate slight changes, if we have a little bit of brain swelling, or a little bit of volume loss. Our three volt spinal fluid and the ventricles by enlarging or decreasing in size, can help accommodate those changes in brain tissue volume. It serves many, many very important purposes.
CAT Scan of a Midsection of the Brain
This is a CAT scan slice that you might see, if you’re looking at a slice through a midsection of the brain. So think about putting on a hat and then taking a picture of what would be inside there across the brim. That’s right about what you would see.
So the left and right ventricles are represented by the large kind of white structures in the middle of this CAT scan image because of less volume, less tissue there, certainly it’s just fluid.
As a result, it looks much brighter in this particular type of image. It’s a kind of a butterfly shape, which is what you would anticipate it should be relatively equal on both sides, and depending on what level at which you take that scan, you’ll see different images because the ventricles at different levels present with a little bit of a different profile.
Ventricle Enlargement
Now, what you might see in the case of ventricle enlargement would be something like this. This is a case of very severe increase in ventricle sizes and you can also see that it’s not symmetrical in nature.
The one on the left which of course is represented with on the right side in this image, they get flipped, like X-rays, that one is a little bit larger than the one on the other side.
What is happening when your ventricles are enlarging is they are pushing outward on brain tissue they are displacing and squeezing brain tissue.
Now that is very problematic in adults because again, the bones in your head have fused together to form form the skull. You now have an issue by which those bones are containing increased pressure.
As you have more pressure within the tissue of the brain, the parenchyma of the brain, what happens is you have less room for vascular expansion.
Oxygen and The Brain
We know that you have to have a constant blood supply of oxygen to the cells within the brain for the brain to function normally. If you deprive brain cells of oxygen, the neurons start to shut down relatively quickly, they need that oxygen as a catalyst to produce energy.
If you’re reducing the amount of blood flow to the brain, in the case where you have this constriction of brain tissue, you’re also going to be concurrently reducing the amount of oxygen available to those cells. And so that is a critical issue, if you have that type of swelling.
Enlargement of the Ventricles
Here’s another series of scans that shows grossly disproportionate enlargement of the ventricles pushing out and compressing tissue. So in severe cases, where you have extreme compression of brain tissue, again, this adversely impact circulation, it adversely impacts perfusion of oxygen throughout the brain.
So in cases where you have severe swelling, you’re going to have a more generalized anoxic presentation of injury, which can then be a secondary process that causes further damage beyond the initial trauma.
Oftentimes, traumatic brain injury results in a cascade of issues that can be much more serious than even the initial trauma. This is one of those cases where if left unchecked, you could have a global hypoxic anoxic injury as a result of the lack of oxygen perfusion throughout the brain.
Hydrocephalus in Infancy
Now, often times people are most familiar with hydrocephalus from the standpoint of infancy. In an infancy when a child is born, there are eight major bones of the skull.
So when you think of the different lobes of the brain, they correspond to that so there are two temporal bones, there are two frontal bones, there are two parietal bones and there are two occipital bones. Now, you’ve got also a whole bunch of bones in the face. When you put all that together, we call that the skull.
Now, when you are born, the bones of the skull in an infant are not fused together, they can have some degree of overlap for the process of passing through the birthing canal, they also have to expand because of the rapid growth of the brain from the standpoint of the size of the brain in early infancy.
Those bones are somewhat flexible. If you get a case where you have an increase of ventricle size in infancy, because the bones of the skull are not yet fused together as they will be in adulthood, they can move apart those bones kind of like tectonic plates on the earth can slide apart, and in doing so it enlarges the size of the head.
And so hydrocephalus, which the Greek words actually mean water, and head, that what that means is that expansion of fluid results in an enlarged skull cavity to accommodate the brain and the increased ventricle size.
In infancy, the most common thing associated which can cause hemorrhage would be prenatal birth, which means that the child is much more vulnerable to hemorrhaging within the brain. There are also issues that can cause hydrocephalus in infancy, which would be a defect in the formation of the neural tube.
So, as the neural tube and brain and central spinal column develop, the central nervous system developed a defect within that tube can cause that as well.
Again, these are very very narrow passage waves through which flows through board spinal fluid. So it does not take a lot of variation for problems to develop.
Arachnoid Cysts
Another means by which this can occur in infancy would be arachnoid cysts. The arachnoid layer is one of the innermost layers that covers the brain.
Cysts within that area, if they are associated with those narrow passageways can easily form a blockage that does not allow that fluid to pass through. Then similar to how it can be an acquired issue in adulthood, it can also be secondary to neoplasms, to tumors within the brain or infection as well. Anything that causes inflammation and swelling within the brain can also be an issue.
Strokes and Brain Injuries
At QLI, with our population of individuals who’ve had strokes and brain injuries, this is a much more common aspect of why we see hydrocephalus within this population.
I think it is probably a much more common issue with the acute phases, because this would be something that would be treated medically in the initial medical stabilization and hospitalization oftentimes, before someone would even get to a level of acute rehabilitation.
We do see individuals who have recently had a shunt placed, or sometimes may need a revision of a shunt for reasons that we’ll talk about in just a little bit.
As an individual ages, though, a more common aspect would be something called normal pressure hydrocephalus that we’ll talk about a little bit further down the road.
Acquired Aspects of Hydrocephalus
Now, the acquired aspects of hydrocephalus.
Intraventricular Hemorrhage
The most often the most common cause of this would be associated with intraventricular hemorrhage. So in other words, the trauma has disrupted the tissue to such a degree throughout the brain, and particularly within the ventricles.
That bleeding has caused blood to be in an area where it shouldn’t be within the clear cerebral spinal fluid of that is coming out of the left and right ventricles and passing into the third, and then subsequently fourth ventricles. The blood itself can block or form a plug within those very narrow passageways. That would be something that would be an obstructive hydrocephalus that is now causing the fluid behind that blockade to build up and to enlarge the ventricle.
It can also block the arachnoid villi that I talked about earlier, that are the reabsorbs and channels that line the outside, and the linings of the brain. If that blood gets into those very small reabsorption pathways, it prevents the fluid from then getting past the blood. It doesn’t take large accumulation of blood for that to occur.
And again, if you think about it from the standpoint of being a drainage system, that is the direction of flow.
If you have a blood clot or a few blood cells that are clotting together, and floating through that clear fluid, it’s eventually going to end up in a drain somewhere.
Now the body does have prothrombin factors in it that help break down clots, and over time, those can be broken down and normal flow can be reestablished.
But that is a potential way that cerebral spinal fluid can either be blocked from getting out of the brain and thereby start to blow up like little water balloons deep within the brain, or and block reabsorption. Either of those is going to disrupt the balance, one would be almost like an overproduction. If the fluid can’t get out of the brain.
The other would be an over absorption, it would be an over drainage problem. Both of those are issues that can affect shunts as we’ll talk about in just a moment.
Swelling of the Brain Tissue
Another very common one from the standpoint of the severe trauma that most individuals who’ve had a severe traumatic brain injury experience, is swelling of the brain tissue itself. Again, these are very narrow passageways, and they pass through brain tissue.
As the brain tissue surrounding those narrow passageways begins to enlarge secondary to the swelling associated with a traumatic brain injury, it can easily close off those passageways, and those passageways will remain closed off until that swelling is relieved.
Now, you know that with post brain injury, acute care, sometimes a section of the skull is removed, and we’ll talk about that before we are done with his presentation as well. That’s done to relieve brain swelling, the tissue itself is swelling and there’s really no way to make the swelling immediately go away.
The only thing that you can do since again, is surrounded by that rigid bone helmet is to take a piece of that helmet off so saw off a piece of the skull and allow that swelling to naturally subside.
So again, from the standpoint of a blockage of the ventricle secondary to brain swelling, that is often a temporary factor, but that temporary factor can last days or weeks, which is why sometimes an extra ventricular drain might be placed.
More acutely, that is what you tend to see more commonly. As I said, similar to infancy, you can have inflammation in the form of meningitis, the lining of the walls can be inflamed and swell and close off that flow passageway. Like everything else, I mean, it is a balance, or if anything is knocked out of whack with this balance, if any of the flow channels are blocked, it reduces efficiency.
If they are completely obstructed, or plugged, you’re going to have a real problem. Because to get the fluid from inside of the brain to outside of the brain, there are very critical choke points that are easily blocked and easily obscured.
Physical Symptoms Associated with Hydrocephalus
Now, what do you see when somebody is experiencing hydrocephalus, these are the physical symptoms that would typically be associated with swelling within the brain are increased pressure secondary to increased fluid collection within the brain. So either the brain swelling itself or hydrocephalus can cause all of the symptoms that you see here. Now, these symptoms represent changes to the function and structure of the brain associated with enlargement of the ventricles and the increased pressure that results.
Vomiting
Vomiting can reflect pressure at the base of the brain, around the brainstem, where it exits the skull in the foramen magnum, that area is very critical from the standpoint of if pressure is put on the brainstem, there are a number of symptoms that you tend to see. Nausea and dizziness is one of those symptoms.
Vomiting is one of the hallmark symptoms that if you go to the hospital with a concussion, that’s one of the things that they tell you, if you start throwing up, you need to come back in and see us. If you get really drowsy and you’re difficult to arouse, you need to be brought back into the emergency room.
Those are symptoms that are associated with pressure on the brainstem as a result of increased intracranial pressure that is now pushing your jello like brain through that opening at the base of your skull where your spinal column exits.
So a part of the brain that should be a little bit higher, a little bit more elevated within the skull is now being mashed down into that opening with the result of these physical symptoms. So that is a critical issue. Because if you have intracranial pressure that spikes high enough, quick enough, you’re going to again lose blood perfusion, you can lose oxygen perfusion to the brain, and you can have permanent damage as a result.
So they tell you, if you start throwing up, you need to come back into the emergency room and that’s exactly what they’re telling you in a way that hopefully doesn’t panic you, is if your brain starts to swell, please come back and see us quickly.
The brain, it’s jello like consistency really means that it is easily malleable. It can move aside when the ventricles are enlarging. It can actually kind of squeeze out through the base of the skull if it is pushed in that direction.
Loss of Coordination
Some of the motor effects of hydrocephalus represent pressure affecting the midbrain pathways of transmission. That loss of coordination, of muscular coordination that can be an inefficiency of the motor information passing down the pathways, the loss of balance can be associated both with the loss of coordination, as well as some of the inner ear aspects.
The nerves that carry the information to and from the inner ear, and particularly those that are associated with the semicircular canals that allow you to know where you are in space and whether you’re moving or what is the orientation of your head body at any given moment. That information can be disrupted because again, those cranial nerves exit around the base of the brain. Pressure on those nerves can result in changes there as well.
Changes in Cognitive Abilities
If the pressure is substantial enough within the midbrain, you can also see changes in cognitive abilities.
Incontinence
Incontinence is a relatively common secondary effect as well.
Sleep and Maintaining Arousal
And as I said before, if you have enough pressure on the brainstem, it can affect the reticular activating area of the brainstem which is involved in being able to maintain arousal in other words to be awake.
There is a part of the brain there that allows you to kind of shut things down and go to sleep at night. If that area is not working correctly, it is difficult to go to sleep and things that can be immediately adjacent to that area such as pain sensation throughout the body that can disrupt it can activate that area.
That’s why it is I mean, if you have a toothache, it can be really hard to go to sleep. It’s because of the pain pathways that the information is being sent through the nerves immediately adjacent to that arousal area, are helping keep it awake activating it.
The opposite effect is if you are not able to maintain arousal, so being very somnolent, being very sleepy at a time when you should be awake and paying attention.
Normal Pressure Hydrocephalus
Normal pressure hydrocephalus is an abnormal buildup of cerebral spinal fluid usually involves again an identified etiology of a blockage that blocks cerebral spinal fluid, that’s obstructive hydrocephalus, but can also be a defect in the reabsorption, which would be a communicating hydrocephalus.
In other words, that is a term that is used to reflect that reabsorption effect. Normal pressure hydrocephalus is considered primarily to be a form of communicating hydrocephalus.
In other words, it is an imbalance of cerebral spinal fluid that results in an enlargement of the ventricles, but without increased pressure.
In other words, it’s not that the ventricles are blocked and the fluid can’t get out. It is a disruption within reabsorption or, it is a disruption of tissue that occurs over time and with aging.
I’m sure many of you are aware of the fact that with normal aging, there is often some degree of volume loss. If there is any type of disease process that volume loss is generally fairly radically accelerated.
You tend to pick it up at an earlier age. There is a normal degree of volume loss and the balance that can be achieved by the ventricular system and production.
Absorption of cerebral spinal fluid means that that volume loss can be made up by having a little bit more fluid within the brain.
If you have enough volume loss, you can actually have substantial increase in the size of the ventricles but without a blockage that is causing that increased pressure.
That would be normal pressure hydrocephalus.
It is easily observed on a CAT scan, just looking at the size of the ventricles. It is also something that is demonstrated by what is called a triad of symptoms.
That’s why it is represented by the pyramid there are three different primary symptoms that you see in normal pressure hydrocephalus. And so if you have someone, particularly again, or after injury has now begun to demonstrate this triad of symptoms.
The first thing that you would conclude in looking at these symptoms is this represents hydrocephalus. This is an enlargement of ventricles.
There’s a variety of potential explanations offered for this idiopathic condition, the most prominent being a disturbance in cerebral spinal fluid dynamics and resistance, brain parenchyma alterations, in other words, volume loss within the brain are vascular abnormality.
So regardless of the specific cause, ventricular enlargement occurs as a compensatory mechanism.
In turn, it results in tissue compression and deep white matter ischemia. So the tracks and pathways that pass immediately over and adjacent to the ventricles, those pathways can be disrupted if the ventricles are enlarged.
This is particularly the case if it happens rapidly. So in a case where somebody has an obstructive hydrocephalus after an injury, because of brain swelling of because of blood tissue within the ventricles, you will see this decline happen relatively rapidly, secondary to the increase of the size of the ventricles and the disruption of the pathways that are immediately adjacent.
These pathways involve transmission of motor information as well as cognitive information to and from the cerebrum to the cerebellum and back and forth.
So that disruption represents a change in that deep midbrain tissue. It can also result in permanent change if it is not treated effectively because of the reduced blood flow secondary to the compression around that area.
So as the ventricles enlarge, whether it is a rapid process are a slow process. As they enlarge, they will press in on the tissue around them reducing blood perfusion. So, increasing cerebral perfusion in the affected areas results in a relatively rapid resolution of these symptoms.
So if you have someone who suddenly is starting to trip more often, they are falling more often, they are more confused and disoriented. And they are now manifesting urinary incontinence. If you have that triad of symptoms, you can be relatively certain that there isn’t enlargement of ventricles.
There’s a compression at a level of midbrain. And this person needs to be evaluated for the potential of having a shunt place to reduce the fluid within the midbrain.
When you have someone who has either because of trauma are because of this normal pressure hydrocephalus and increased ventricular volume that is affecting these physical and cognitive functions. Reducing the cause, which is the increased size of the ventricles typically results in a resolution of those symptoms relatively rapidly.
Again, if extensive ischemic changes occur because this is allowed is allowed to go on for an extended period of time, you tend to get more severe symptoms, and you get poor prognosis.
Number of Cases of Hydrocephalus
Now some of the data that I’ve seen on normal pressure hydrocephalus indicates that there are anticipated approximately 700,000 individuals in the United States that suffer from normal pressure hydrocephalus, but only about 20% of those cases are actually identified and treated.
So in an elderly population, this combination of symptoms that perhaps 50 or 100 years ago, we would just say represents aging, you can’t walk as well, you tend to stumble more, you start to get more confused, you forget things and you become incontinent of urine much more frequently, that could represent something that is a reversible process, and so needs to be evaluated.
What we tend to see with our brain injury population is either obstructive issues associated with bleeding within the ventricular system, which blocks the fluid and has to be treated are a swelling of tissue from inflammation or are just swelling of the tissue itself.
Now, most individuals that are coming to us from a post hospital rehabilitation standpoint, are past the point of which that immediate acute response to injury is swelling with brain tissue. That is pretty well taken care of itself by the time most folks get to us.
And again, the reversible aspects of that blockage of those narrow passageways when the swelling goes down means that most individuals if they don’t have an occlusion of those cerebral aquadex will return to normal function from the standpoint of cerebral spinal fluid production and re absorption after their injury. For those who do not, for those who have some type of obstruction that is necessary to get the fluid out of the ventricles and absorbed somewhere else in the body, ventral peritoneal shunt is the most common thing that we see.
Ventral Peritoneal Shunt
Now, as we’ll talk about in a minute, there are other places the fluid can be shunted to, but this tends to be in the vast majority of cases after traumatic brain injury or blockage as a result of stroke, this tends to be the procedure that we see.
It is used to treat hydrocephalus by basically providing an artificial aqueduct a bypass of whatever has caused that fluid to not be able to pass through the normal passageways.
It shunts the fluid from the ventricle to some other area of the body and the most common one that we see is the peritoneal cavity.
It relieves that increased intracranial pressure, which is causing the pressure on the brain. That can get really critical really quickly. So it is something that typically needs to be treated when you see the symptoms start to emerge.
Ventral Peritoneal Shunt Components
This is an overall view of a relatively simple catheter. The ventricular catheter is passed through a hole in the skull into the brain.
It is pushed into and through brain tissue and again, because brain tissue is kind of like jello, it can kind of move aside provided that whatever is introduced to it is introduced without a great deal of force.
So because it is relatively small, it can push tissue aside without doing a substantial amount of damage to brain tissue in order to get the fluid out.
Ventricular Catheter
The ventricular catheter goes into the ventricle, it is attached to the shunt itself and we’ll talk about different types of valves and how they might be arranged.
Then there is the distal catheter that is passed under the skin down into the gut cavities into the peritoneal cavity.
Valve
Traditionally, different shunt types have relied on different aspects of functioning, the vast majority that we’re going to see now, modern shunts tend to be the one at the very bottom on your right, which is the ball and cone with a spring valve.
The earliest shunts were simply a tube that had a slit and so it depended upon the physical properties of the plastic or silicone itself as to when that slit would allow something to pass that or a mitral valve, that if there was enough pressure upstream, would push that fluid out through the opening.
From there, they went to more of a diaphragm type of valve and the ones now are either ball and cone or diaphragm, that can be adjusted.
They are typically based on either pressure or regulated within the valve itself by flow rate, so you can set a particular flow rate.
And then you observe the symptoms following that. So the couple of days that somebody might spend in a hospital, after a shunt is put in place is so that they can look at different flow rates and make sure that they’re not over draining, which can cause other problems or that they are adequately getting fluid out.
Valves now can most often have some type of siphon regulation on it. That is basically helping manage the hydrodynamic forces involved in changing orientations. So when you get up, your body changes, how fluids in it need to be regulated.
Saw something recently that said, well, I’m old enough to appreciate this, if I want to get a thrill, all I have to do is stand up real fast, so you can get lightheaded if you do that.
It can also again change fluid dynamics.
Having a valve that can accommodate for that, so that you don’t over or under siphon off fluid is a way of looking at that.
Then I said a little bit earlier, the peritoneal termination for the shunt is what we see most often in our population, but there are also conditions in which it might be vented to another area within the body.
The valve on the shunt itself tends to be made up of a variety of different stages.
As you can see here, there’s an input there with a proximal occluder. So that keeps it from shifting and going back the wrong direction. There is a silicone dome. This valve is generally for most individuals that we see that have this implanted after a traumatic brain injury or stroke that is occluded, the ventricles tends to be located behind either the left or the right ear.
So you’ll see with an individual who has had one of these put in place, a little bump back there and that bump is actually that reservoir, that reservoir can be pumped to look at flow, to make sure that flow is paitent.
The adjustable valve mechanism represented there is something that allows the ball and cone type of valve to be adjusted so that you can have a higher flow rate or a lower flow rate depending on the amount of pressure coming from upstream.
Distal Tube
The outlet connector is where that distal tube is connected, that is then threaded underneath the skin down into the gut cavity. You see all that radio, valve catheter indicators, these are basically materials that allow you to be able to observe where everything is and where it’s set when you look at it through an X-ray. So being able to take an X-ray and see what’s going on.
How a Shunt Works
Here is a image of a shunt. And again, I am not associated with or selling any type of shunts, so I’m trying to keep company names off of things to the degree that I can.
The reservoir pumping, the reservoir as you see there can look for potency checks and it can check the access port make sure that things are flowing like they’re supposed to.
Suturing holes that allow you to anchor the valve there so when it is first put in, again it is going to have to be anchored somehow because it’s going to take time for the tissue around it to move back into place and allow that to stay where it should.
Then if you look here, the spring that goes to this device right here, this device has different levels on it. So in other words, it’s almost like a helix. It’s like a spiral within a spring.
As you turn that you can either make the spring tighter or lessen the pressure on the spring. So in other words, you can make it easier for fluid to flow through, or you can make it more difficult for fluid to flow through.
There are many, many, many, many different types of orientations and valves, as you can see here, with a variety of ways in which you might put, so again, it depends on the amount of fluid that you’re going to need to vent off.
This is a couple more here on the upper right, these would be the valves themselves, those little black marks that you see on it with the little diagram, the little arrow and the little dot.
That is that radiographic information that I was talking about earlier.
So if you look at it at an X-ray, you will actually see those and it shows you which direction things should be going.
Right immediately below those are magnets, those are those round things that are marked with blue and white.
The round disc that I talked about earlier that allows you to adjust the pressure on the spring can be adjusted by way of these magnets.
So you can put a magnet over that, and you can adjust it by turning it. So that allows you to adjust the shunt without having to physically go back inside the skin, you don’t have to make another incision so it reduces the risk of further infection associated with the shunt, so that if you have to have some type of adjustment, it can be done very easily in your doctor’s office, it’s not much of a procedure at all.
If you need to increase or decrease the flow. If the flow is not high enough, if you’re not shunting off enough fluid, you’re going to get the same symptoms that you would expect with hydrocephalus.
If you are shunting off too much fluid, you’re often going to have headaches associated with that, because of the tissue that surrounds the brain. So, you can change the opening which is called programming the shunt.
This is what it looks like when you look at it with an X-ray. So different settings for a particular valve are represented here. A physician looking at this could be able to see exactly where it is currently set and could make a decision on the basis of that of how much you want to increase or decrease the amount of flow.
Ventriculoperitoneal Shunt Placement
As I said, the shunt placement goes from an incision that is made behind the ear to allow for placement of that valve, and for the drilling of a small hole in the skull through which that ventricular shunt is placed.
That tubing goes through brain tissue into the ventricle goes to the valve and then in a subcutaneous threading it is sent down into the peritoneal cavity where it is anchored on the far end. Or in the lower example in an atrium of the heart, where you would dump the fluid off.
Excess fluid within the brain is basically shunted away and put down into a different area of the brain.
Decompressive Craniotomy
Also, if you have to relieve pressure because of swelling within the brain itself, you will see sometimes a decompressive craniotomy or decompressive craniectomy.
Now sometimes these terms get used a little bit interchangeably but they’re really not.
An automate is when you put a hole in something when you cut or separate and ectomy is when you take something that should be in the body out.
So a craniectomy is removing a part of the cranium, so removing a section of the skull is called a craniotomy.
Sometimes you need to get into the brain to do surgery, you perform a cranioectomy and you do your surgery and then you perform cranioplasty and you put the skull back in place.
Sometimes if a person has had substantial swelling, that craniectomy will be left out for a substantial period of time until the swelling has gone down or until the individual is considered to have recovered enough that they can tolerate going back under general anesthesia for the cranioplasty procedure.
There are times when a person has enough swelling that they will do both of these procedures at the same time they will do a craniotomy and put a shunt in place.
If there is enough concern regarding increasing size associated with the ventricles.
The procedure is conducted under general anesthesia procedure without complications to put a shunt in place generally only takes about 90 minutes open to close, so it is a relatively rapid process.
As I said you would make an incision behind the ear and there we go. That is and then drill a small hole in the skull, the catheter is threaded into the brain through that hole that attaches to the valve.
The other end of the valve connects to a catheter that goes down through the chest and abdomen and that allows the fluid to be shunted away.
Hospital Recovery After Implantation of a Shunt
Hospital recovery after implantation of a shunt is typically a two to three day process. replacement of a functioning shunt might not be necessary for several years and the obstructive issues that are associated with the need for that if they resolve during that time, then the shunt is simply there it is not doing anything.
Shunts sometimes are no longer needed, and can be removed. In my experience that is a relatively rare process. It is not often the case that a shut will stop working with time one statistic that I said one statistic that I have read associated with students is that there is a 100% failure associated with chance given enough time kind of like mortality with existence it is 100% given enough time.
Shunt Failure Rates
The failure rate for shunts after placement is typically around 10 to 20% failure rate within the first year and around 5% thereafter. So, if you look at those numbers, that means typically somewhere between 17-19 years after a shunt is placed, it is probably not working anymore.
Again, if the reason the shunt went in place was because of inflammation and swelling, it is quite likely that that will resolve over time, if it is obstructive because of blood products. Again, that will likely resolve itself over time.
The need for a permanent shunt is more associated with issues like developmental defects associated in infancy that might necessitate a shunt permanently.
There are risks associated with going in and doing anything with the brain, and so that’s why I think shunts often are not removed, after they are put in because there is a risk.
Those risks can be significant. I mean, it can be subtle intellectual or developmental declines intracranial hypertension, irreversible tissue injury, even death associated with going in and pulling a shunt out.
It is not without risk. And so for that reason, the classic if it ain’t broke, don’t fix it tends to apply in this case, if it’s not causing a problem, it tends to be benign, and so it tends to just stay there. So there are a lot of factors that can go into making that decision of taking that out.
But, again, in my professional experience, I don’t see that happen very often even in cases where people have headshots for 20 plus years.
The craniectomy process, if the the brain tissue itself is swelling, which is now squeezing off those narrow passageways, relieving that pressure can remove the need for having a shunt put in place. A craniectomy often will serve that purpose if the obstruction is secondary to brain tissue swelling.
Again, if cerebral swelling goes up rapidly enough, then the intracranial pressures prevent oxygen perfusion secondary to blood flow, and you have to relieve that pressure.
The only way to do it is taken off, palm sized piece of the skull or more to allow the brain to swell.
That process that the knowledge that that can actually save an individual after a brain injury has existed for a long, long time the Egyptians wrote about it. The tools are a lot better now than they were at that time. The survival rate for the surgery I’m sure it’s probably gone up fairly dramatically as well, but this is not a new thing.
Bone Flap Surgery
Typically, you drill a hole and then you use that hole as a starting point to cut around to take out the what’s called a bone flap.
Used to be the bone flap was sent to a freezer in the hospital where they took it out and then it was taken back out of the freezer at the point that they want to put it back in place.
There are of course issues associated with freezing and thawing out human tissue. So oftentimes nowadays, it will actually be implanted into the body.
They’ll make an incision in the peritoneal cavity and they will put it into your gut cavity. different set of risks associated with that, but it is your own tissue. It doesn’t tend to be rejected by your body.
You can develop adhesions, if you prone to those. So there are, as with anything risks associated.
Post-Implantation Risks/Considerations
I’m running out of time, so I’m going to have to go quick. I’ll skip reimplantation. So, post implant risks and considerations.
Shunt malfunction
If somebody has a shunt put in malfunction relatively common, it’s usually some aspects of mechanical failure are blockage of one or the other ends of the tube.
In other words, blood for example, within the ventricle can block the tube as easily as it can block then the natural passageways.
Primary failure can occur secondary to obstructions it can be a disconnection or a break migration of where things are located or even leakage, so it may need some adjustment of settings. You can also again, develop adhesions with these devices as well.
Anything that blocks the intake is going to require a physical revision, because you’re going to have to replace the tube or move it and either way, you’re probably going to have to open up the head to get in to do that. Small bleeds are fluid collections in the skull can occur as well.
If you rapidly decompress the ventricles, you can also create other problems. So in other words, if you decrease the brain’s volume by dumping a bunch of fluid out of there really, really fast that bridging veins that go between the outer layers of the inner layers of the skull and the outer layers in the brain.
Those bridging veins can be torn as a result of rapidly decompressing fluid. So in other words, they have adapted. This is more in cases with long standing hydrocephalus.
If the bridging veins have adapted to that decreased space between the brain and the skull, and then suddenly you increase that space by dumping a bunch of fluid out of the midbrain, the brain itself shrinks and can rip and tear those bridging things.
Hematoma
You can have a hematoma on the surface of the brain secondary to taking too much fluid out too quickly.
Exposure to Magnetic Fields
Because these can be adjusted by using a magnet, you also have a risk of being exposed to magnetic fields. So nowadays, this doesn’t tend to be the problem because the substances that they use to make these devices are less vulnerable, you can go into an MRI with a modern shunt.
With older shunts, that’s not the case. You don’t want to go into a very high magnetic field with something that is inside of your skull that might get wiggled around as a result of that high magnetic field.
The biggest risk, of course, with exposure to magnetic fields is that you’re going to change your settings. If you dial down or dial up the amount of flow as a result of an inadvertent exposure to a magnetic field, that’s going to need to go back and be adjusted back to a setting where it should be.
Monitoring the Shunt
There are some new technologies associated with these as well using micro tech sensors to monitor the shunt.
The one that I’ve seen now that is currently starting some human trials is basically the size of one of those little small dot band aids.
It contains information that can send a wireless signal to an app on your phone or on your computer to tell you how well your shunt is currently operating.
Whether or not there are conditions detected, that would predict failure of that shunt, and roughly give you a timeframe on it.
These are things that are not quite get ready to roll out for consumer but are currently being being evaluated.
Post-Op Instructions
After your shunt placement, you’re generally going to get some post op instructions, like don’t mess with the valve for a little while, let that settle. It’s okay to lie on the side of your head where the shunt valve is located, so don’t worry about what side you sleep on.
Activity Restrictions
For about six weeks, you’re usually going to have to avoid some activities that might otherwise cause you hit your head.
As a neuropsychologist, I would advise you not to hit your head in most instances, but I think it is a little bit more critical when you have something like this that is not yet anchored by all the tissues in your body and is extending from the outside of your skull into your brain tissue.
Avoiding lifting anything heavy, typically, you’re told no more than five pounds for some period of time, no housework, no yard work and avoiding alcohol.
Those are all things that they’ll tell you right off the bat. The alcohol is more for concerns for falling than anything else, quite frankly.
Watch for Infections
Watch for signs and symptoms of infection and like anything else where you have an incision.
Showering and Bathing
Don’t swim or bathe until the stitches are stapled to get removed shower without letting the water hit directly on to the incision area.
Wound Care
You can wash it with some warm soapy water and gently pat it dry and change bandages as need be.
Eating and Drinking
Resume a normal diet. Constipation is not uncommon following surgery because of some of the medications that are often used, and it can be associated with some of the meds that are given for post surgical pain.
You want to avoid constipation simply because of straining for bowel movements is going to radically increase vascular pressure inside of your skull. You want to avoid that as much as you can.
So fiber supplements are often suggested after a shunt placement for a few weeks, you have to let the folks know there’s going to be some degree of discomfort associated with the incision, but to watch for changes of redness, stiff neck fever, things like that.
References & Resources
That brings us to our references, the hydrocephalus association. The third one listed there is actually a very good resource that I would suggest if anybody wants more information on hydrocephalus or shunts, either one. These are further resources as well, that should be available to you within your PDF. And with that, I will wrap up and thank you very much for your attention throughout the program.
Spinal Tap
Tim Benak 1:02:36
Why do Spinal Tap? If a patient shows all the symptoms? What does the analysis yield?
Dr. Snell 1:02:56
Well, what you’re doing with spinal tap is you’re drawing off some cerebral spinal fluid because you only typically have about 120 to 150 milliliters it doesn’t take very much to change the amount of cerebral spinal fluid in currently in your system for a short period of time again, your body is going to produce more of it.
But if it is an overabundance, if it is communicating hydrocephalus, if there is a reabsorption problem, what you will typically see is a resolution of the primary symptoms associated with that communicating hydrocephalus almost instantly, when you draw off some of the fluid.
So what you’re effectively doing is by going in and drawing off some fluid, you’re doing what a shunt would otherwise do. And you’ll get to see the temporary effects of that if what you see is a pretty quick resolution of symptoms, it tells you right away, what we need to do is get more fluid off. So that would indicate Oh, gosh, that would be necessary.
Categories: Brain Injury