Interstellar Brain Monitoring
Remember standing on your head as a kid? After a minute or so you felt lots of pressure? Scientists say the same thing happens when astronauts fly into space. Without gravity, blood flows to the head, which could cause vision changes and impact future missions. Now new cutting edge devices could help answer those questions and help us here on earth.
Exploring space. For retired astronaut Ken Bowersox, there's nothing like it.
"It's kind of a dream like experience to be able to float around while you're working," Ken Bowersox told Ivanhoe.
Bowersox completed five missions including one to the International Space Station. But a weightless environment can take its toll.
"On every one of my flights," said Bowersox, "I noticed that additional pressure in my head."
NASA scientists believe the loss of gravity is putting pressure on the brain, causing vision changes in astronauts that could jeopardize future long term missions.
"There's a number of changes in the microgravity environment," Eric Bershad, M.D., Neurologist and Neurointensivist, and Assistant Professor of Neurology and Space Medicine at Baylor College of Medicine told Ivanhoe.
That's why Dr. Eric Bershad has developed a new non-invasive way to measure brain health without the use of a spinal tap or hole in the skull.
"This could potentially not only benefit astronauts, but also millions of people on earth," explained Dr. Bershad.
Using an ultrasound, the device measures blood flow through the eye artery.
Another device developed by doctor Chethan Rao called Cerebrotech uses low energy radio waves to measure brain volume changes.
Both devices could be used as an early detection for brain injuries in space or here at home.
The devices could help the two-million patients admitted to hospitals for strokes and brain trauma each year.
In space, we could see a yearlong mission on the International Space Station next year and future missions to mars could last two to three years, making work in this area critical for its success.
BACKGROUND: Intracranial pressure occurs when there is a rise in cerebrospinal fluid, which surrounds the brain and spinal cord, or when there is a rise in the pressure in the brain itself. The causes can be a mass in the brain, bleeding into the brain/fluid around the brain, or swelling within the brain. This pressure can damage the spinal cord or brain by pressing on important structures or restricting blood flow to the brain. This condition can't be prevented; however common causes of intracranial pressure include, but are not limited to, tumors, head injuries, aneurysms, hemorrhaging, stroke, and meningitis. Headaches, blurred vision, changes in alertness, seizures and other neurological problems are signs to seek immediate medical attention.
TRADITIONAL MONITORING: Traditional Intracranial Pressure Monitoring (ICP) can be done three ways which involve drilling into the skull. The most accurate procedure is by using an interventricular catheter; a hole is drilled into the skull and the catheter is inserted into the lateral ventricle which contains cerebrospinal fluid. The ICP method can drain fluid through the catheter while monitoring. If monitoring needs to be done immediately, the subdural screw method is used; a hollow screw is inserted through a hole drilled in the skull and placed through the dura mater, allowing measurements to be taken from inside the subdural space. An epidural sensor is less invasive than the other methods; once a hole is drilled in the skull, the sensor is inserted between the skull and dural tissue. This procedure will not remove excess cerebrospinal fluid.
NEW TECHNOLOGY: In collaboration with the Kaunas Institute of Technology in Lithuania, Eric Bershad, M.D., of Baylor College of Medicine and the National Space Biomedical Research Institute have developed a new non-invasive way to measure ICP and assess elevated brain pressure in patients and perhaps future astronauts. Dr. Bershad told Ivanhoe that the Vittamed device uses ultrasound-based measurements through the eye artery, "since the ophthalmic artery runs both inside and outside of the skull, the intracranial pressure will affect the way blood flows in the part of the artery inside the brain. This can be compared with the flow in the extracranial eye artery segment. The differences can then be analyzed to determine the intracranial pressure." Another device developed to measure brain volume changes is Cerebrotech which can detect early stages of brain bleeding or swelling using low energy radio waves. The future vision of the device is to allow astronauts to continuously wear it to monitor changes in cerebral fluids.
FOR MORE INFORMATION ON THIS REPORT, PLEASE CONTACT:
Sheryl E. Taylor
Senior Coordinator Mktg. Comm.
CHI St. Luke's Health
Eric Bershad, M.D., Neurologist and Neurointensivist, and Assistant Professor of Neurology and Space Medicine at Baylor College of Medicine, discusses a new non-invasive way to measure brain health – which can be used for astronauts and people suffering from brain trauma.
Interview conducted by Ivanhoe Broadcast News in August 2014.
Give us an idea of what you think is happening to astronaut's brain health while they're in space.
Dr. Bershad: There are a number of changes in the microgravity environment aboard the International Space Station which alters the physiology of the body. Some of the major changes are the loss of gravity which causes an upward fluid shifting toward the head. Some of the other differences are that the carbon dioxide level is much higher due to less ventilation on the International Space Station , and that may increase the pressure inside the skull due to too much cerebral blood flow. There is also a high salt diet which may cause fluid retention and also contribute to the extra fluid inside the skull, as well as a very resistance-based exercise program which was designed to avoid muscle and bone loss. But there may be some evidence on Earth that by doing this straining maneuver that, that may actually impair some of the blood flow leaving the brain and may also contribute to the problem. Whether straining maneuvers affect the venous drainage of the brain in space needs to be explored. There are investigations underway to try to determine which of these factors may be responsible for the visual impairment that is likely due to elevated pressure inside the skull.
You said they had a high sodium diet?
Dr. Bershad: They have a very high sodium diet compared to the dietary recommendations on Earth, but I've heard more recently that they are trying to work on cutting down the salt intake. Another interesting phenomenon is that some of the astronauts complained of a stuffy nose and that the taste and smell are different in outer space – because they can't taste as well, they prefer a salty and spicy diet. I also have heard that there are other reasons for the high salt content in that historically, the space diet may have been adapted from the military diet.
What kind of impact can this fluid buildup have on the human body?
Dr. Bershad: Fluid buildup in the body in the setting of lack of gravity may impair the drainage of fluids including blood and cerebrospinal fluid from the brain. This may lead to pressure on the back of the eye, which may change the vision. We do not yet know whether all of these changes are reversible. It is uncertain yet whether there may be other subtle changes in cognitive performance or other brain functions after a prolonged exposure to microgravity. We know that in order to study the problem that's happening in the majority of the astronauts, especially the long-duration astronauts, is that we're looking for ground based analogs to address a similar condition. Unfortunately there's no perfect condition because there is no way to completely simulate microgravity on earth. There are some patients that have chronic elevated intracranial pressure which is the pressure inside the skull and they also have visual changes which look similar to what the astronauts are developing. By studying some of these ground-based analogs we can hope to learn something about the pathophysiology that may be leading to these chronic changes in some of the astronauts.
Besides the visual disturbances is there anything else that you're worried about?
Dr. Bershad: There are other reports of occasional headaches in astronauts and this was reported in an anonymous survey that a significant majority of the astronauts were having headaches whereas none of them headaches when they were on earth. And it's also possible that some of those headaches may be related to a similar problem especially if there are elevated carbon dioxide levels.
All of the pressure and so forth?
Dr. Bershad: Right. There are some moves to try to lower the carbon dioxide levels but it's very energy intensive to remove the carbon dioxide. That may be one of the limiting factors.
How will this device help?
Dr. Bershad: Currently on earth if we want to get an accurate measurement of intracranial pressure it requires an invasive procedure such as a lumbar puncture which is a spinal tap. We're putting a needle into the lower back or a hole through the skull and measuring through a catheter through the cerebral spinal fluid space, called the ventricles, or within the brain itself. On the International Space Station, even though the lumbar puncture carries fairly low risk, if there is a complication then that could potentially jeopardize the mission for that astronaut and create huge expense to evacuate the astronaut. What I'm doing with my project is trying to evaluate a noninvasive intracranial pressure device. Currently we don't have that sort of device on earth either so this could potentially benefit not only the astronauts but also millions of people on earth that require an accurate measurement of their intracranial pressure.
How exactly does it works then? You said it's not something that can be self-administered at this time; it would be something that you would have to have someone administer?
Dr. Bershad: The device uses ultrasound and it is currently a technology that is used on the International Space Station. This specific device looks at blood flow through the eye artery which is called the ophthalmic artery, and because the ophthalmic artery runs through the brain and then part of it runs outside of the brain we can look at the way the blood flowing through that artery is affected by the pressure inside the skull. Similar to a garden hose where if the water flowing through that hose if you pinch the hose then that changes the characteristics of how the water is flowing. By that same principle we can look at the difference between these two different parts of the eye artery and see the difference between the part inside the skull and outside the skull. Then we try to balance the appearance of the flow by putting some gentle pressure on the eye and see how much pressure it takes to balance these two segments.
You mentioned that this is going to have benefits to those on Earth; can you talk about some of the specific conditions?
Dr. Bershad: There are many patients that may have traumatic brain injury or that have what's called hydrocephalus where they have too much fluid in the skull. Or patients with bleeding in the brain, and patients with strokes, so there's many conditions where it would be beneficial to be able to follow the intracranial pressure and see the response to treatment, determine if their pressure is high but not have to do an invasive procedure each type.
Did you want to say anything else important?
Dr. Bershad: The other thing I wanted to mention is that one of the main goals of the National Space Biomedical Research Institute is to try to identify technologies that will help with the astronaut health but also apply that to earth-based medicine. Some of my other colleagues, such as Dr. Rao, are also evaluating brain physiology monitoring techniques as well. It's not going to be just one. In order to understand this complex syndrome that the astronauts are developing it's going to really require a multi-disciplinary approach to determine what's happening with the brain physiology.
What is Dr. Rao working on?
Dr. Bershad: He's working on another device that uses radio waves through the skull. It looks at changes in the volume inside the skull using a noninvasive radio wave device that looks at how the radio waves are being changed by changes in the intracranial volume. However much volume is inside the skull, determines what the pressure is. Since the astronauts have fluids shifts to the heads which causes more volume inside our skull, then if we can noninvasively determine how much volume is there and what caused that volume to increase, then we may have some ideas of pressure changes and also changes in the eye.
You talked about the fluid in our body kind that pushes up into our chest and into our heads. What is being done now to try to keep that away?
Dr. Bershad: That's a very good question. There are both medications but predominantly mechanical countermeasures to actually suck the fluid back down into the legs to restore artificially the gravity. One of the things that can do this what's called lower body negative pressure boots. What those do is those create a vacuum effect in the legs and it traps the venous blood into the legs to avoid the fluid shifting up toward the head. That's something that anecdotally from some of the astronauts that I've spoken to, they say that they feel that their head congestion is relieved after they put the boots on. But then once you turn them off then they have a rebound fluid shifting toward the head. Mostly, these boots have been used in the past for preparing the body for re-entry to Earth gravity, to reduce the acute effects of gravity on the cardiovascular system.
Describe the study that you're doing where you're actually working with healthy people.
Dr. Bershad: The study that I'm working on is taking a research prototype that was invented in a lab in Kaunas, Lithuania and trying to further modify it for our needs in space. In healthy subjects, we assessed how easy it was to operate the device, how repeatable, and also whether 2 different operators performing the procedure on the same subject would have similar results.
Next, we wanted to validate it in a clinical basis to see if it's accurate compared to the invasive lumbar puncture measurements of intracranial pressure. What I'm doing over at St. Luke's Medical Center at CHI Baylor, is comparing the noninvasive ultrasound device at the same time in patients that are already having a lumbar puncture done for a medical condition. That way I can compare if the noninvasive ultrasound device is accurate compared to the invasive measurement which we're using as the gold standard measurement.
Just in your normal everyday patients that are getting that done; and then you're also using your device and comparing the two?
Dr. Bershad: Right. We have a number of patients that require lumbar puncture for diagnosis of their medical condition. If they require a lumbar puncture for a clinical need then we try to recruit them into the study and see if they are willing to put the helmet on with the ultrasound probe and let us take a noninvasive measurement at the same time – in addition to the lumbar puncture.
Can the utility of this be used prior to launch, immediately after launch and so forth, perhaps in future versions? Explain that.
Dr. Bershad: One of the potential benefits of the device that I'm testing is that because it's noninvasive, then you have the ability to check each astronaut multiple times and that way we can tell what is happening to their intracranial pressure compared to before they go into outer space. And then, under different conditions on the International Space Station can then see if there are certain activities that may be increasing their intracranial pressure. We can use it to follow them after they come back to earth and see if that condition resolves. Because right now we don't know what the intracranial pressure is and what factors are affecting that.
Right you don't have a baseline to work with?
Dr. Bershad: Correct. Currently only a select number of astronauts have invasive lumbar puncture measurements and that's usually after they come back. But we don't know what the intracranial pressure is while they are actually up in the International Space Station, so one of the major goals of NASA is to noninvasively measure the intracranial pressure they've discussed -- trying to invasively measure the intracranial pressure but that brings significant increased risk which may not be justified.
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