BACKGROUND: A brain aneurysm is a bulge in a blood vessel in the brain. It can leak or rupture, causing bleeding into the brain (hemorrhagic stroke). Usually a ruptured brain aneurysm occurs in the space between the brain and the thin tissues covering the brain. This type of hemorrhagic stroke is called a subarachnoid hemorrhage. When an aneurysm ruptures prompt medical attention is needed. However, most aneurysms do not rupture, cause symptoms, or create health problems. (Source: www.mayoclinic.com)
SYMPTOMS: A severe headache that comes on suddenly is the key symptom of a ruptured aneurysm. It is often described as the "worst headache" ever experienced. Other symptoms of a ruptured aneurysm can include: nausea, vomiting, blurred vision, stiff neck, seizure, confusion, sensitivity to light, drooping eyelids, and loss of consciousness. In some cases, an aneurysm can leak a small amount of blood into the brain, called sentinel bleeding. It can cause the sudden, extremely severe headache too. A severe rupture usually follows leaking. An aneurysm that is not ruptured may not produce any symptoms if it's small, but a large one can press on brain tissues and nerves causing: a dilated pupil, a dropping eyelid, change in vision, numbness or paralysis on one side of the face, and pain above and behind an eye. (Source: www.mayoclinic.com)
NEW TECHNOLOGY: Aneurysms can be detected and treated before they rupture, usually with minimally-invasive endovascular coiling or surgical clipping. Surgery involves placing a small metal clip around the aneurysm to isolate it from normal blood circulation. It will decrease the pressure on the aneurysm and will prevent it from rupturing. Surgery will depend on the size of the aneurysm and the general health of the patient. In the endovascular procedure, the aneurysm is first assessed by inserting a catheter into an artery in the patient's leg into the head. Tiny platinum coils are threaded into the catheter into the aneurysm until all of the space inside it is full. The coils block blood flow and prevent it from rupturing. This method is great for smaller aneurysms. For larger ones that have a high rate of recurrence, the coils cannot fill the vessel. Now, doctors use Onyx to fill them. Onyx is a thick black substance that turns solid when it is exposed to blood. It is an ethylene vinyl alcohol copolymer that was FDA approved in 2007. Onyx is injected into the brain through a catheter. Whenever the aneurysm is filled, the procedure is complete. (Source: www.bafound.org)
Dr. P. Roc Chen used this treatment for arteriovenous malformation (AVM), or abnormal connection of blood vessels. When AVM occurs, a tangle of blood vessels in the brain bypasses normal brain tissue and directly diverts blood from the arteries to the veins. More than 50% of patients with an AVM have an intracranial hemorrhage. Patients can have localized pain in their heads due to increased blood flow around an AVM. Fifteen percent of AVM patients might have trouble with movement, vision, and speech. During treatment, doctors place a catheter inside the blood vessels that supply the AVM and block off the abnormal blood vessels. Then the Onyx, micro coils, and particles are used to stop blood flowing to the AVM. Treatment, of course, will depend on the symptoms the patient is having, the type, size, and location of the AVM. (Source: www.strokeassociation.org)
Peng Roc Chen, MD, FACS, FAANS Cerebrovascular Neurosurgeon, Director of Cerebrovascular/Endovascular Program at the Mischer Neuroscience Institute at Memorial Hermann-Texas Medical Center, talks about a life-saving endovascular "glue."
How rare was the problem that Lauren had?
Dr. P. Roc Chen: This is one of the very rare conditions called dural AV fistula, which probably affects less than 1 in 100,000 cases in the population. It occurs more often in adults but can occur in pediatric patients as well. Sometimes it can be related to middle ear infections, but in Lauren's case, she didn't have any of these pre-current conditions.
So why it happened is unknown?
Dr. P. Roc Chen: Well, we had a lot of speculation. This is a condition that we've known can happen; however, we do not know exactly what occurred. We do suspect some kind of endogenic factors, related to programming in a way, which could be part of the factor. Also, it could have been a problem related to blood clotting in the veins' outflow from the brain, but we still don't know which one occurred first.
Can you describe the situation? Basically the blood wasn't able to get out of her head right?
Dr. P. Roc Chen: Right. Normally you have an artery coming from the heart through the neck into the brain, which basically carries blood and fresh oxygen to the brain: from high speed flow, down to very slow speed flow, to the small vessels called capillaries. Once it delivers the nutrients and the oxygen, it slowly gets recollected into the outflow channel, which is supposed to return from the brain to the heart and these channels are called veins. Ultimately it will go into very large veins called venous sinuses, which are the main channels along the middle of the head. The midline of the brain is between two hemispheres. It comes to the back, traversal around both ways, and then joins through the neck down to the heart. The flow difference between these veins is different from the arteries. The veins flow at extremely low pressure and slow speed; whereas the arteries are at high speed and high pressure. That's the way to make circulation happen. When something happens to block these channels, the main channel returns to the heart with increased brain pressure because the brain would not be able to return all the blood to the heart very well. Lauren had a tremendous occlusion, meaning that blockage with all the main channels to get out of the brain. Virtually she lost the two main outflow channels that are supposed to return the blood, called a venous sinus occlusion.
Imagine that the fistula is a driving rotary and there are multiple street roads connecting to the rotary. If you just block one road getting to the rotary, you don't fix the problem. You have to use a certain way to fill and seal the entire rotary to block every single street connection that will block the entire fistula from being entered. That's one part, but also you don't want this liquid material called Onyx ("glue") to be overused. The glue can be injected into it, but over-pushing can cross the line into the normal part of the flow channel. That will also be a problem because that will block limited normal outflow. So that's the challenging part. We were able to use a couple of small arterial accesses and ultimately push just enough of the liquid material, or "glue", to seal the entire fistula-like rotary by preserving the normal outflow. Before it was done she was in a coma and also was having what we call status seizures. That basically means that her brain was constantly seizing. But as soon as the procedure was done, the seizures stopped, she woke up quickly and ultimately recovered completely.
If the glue is not used for that, what is the material usually used for?
Dr. P. Roc Chen: The material is one of the polymers with the commercial name called Onyx. It's one of the materials developed a few years ago which now is used very frequently in the neuro-endovascular procedure to try to seal certain abnormal vascular malformations. It is used to seal something like dural AV fistulas, abnormal vessels, or arterial malformations. You have a short amount of time to deliver these liquid materials, following the artery and then letting them solidify, forming a concrete appearance and sealing the vessel.
Where in the body would you usually do that?
Dr. P. Roc Chen: It's originally developed for the brain for normal vessel treatment. Now we use it in many parts of blood vessel treatment and any kind of endovascular procedure, for the liver abnormal vessels similar to the brain, and even some vessel tears that want to sacrifice the vessel.
Can you talk about the MRI scan she had when she was three?
Dr. P. Roc Chen: When she was three years old, her head growth was on the high portion of the growth curve so she was referred to have an MRI scan. On the MRI scan, her venous channel was open, which was normal at the time. So something happened between three years to the time this occurred when she was nine years old. Something occurred that occluded the main channels in between those stages.
So the blockage actually caused the circulatory system to find other paths?
Dr. P. Roc Chen: Right. There were issues along the way. The blockage occurred in the brain. It's almost like if you're driving on an eight-lane highway and all of a sudden that highway gets shut down and now there is only one lane. So, you can see the traffic jam and, in the traffic jam, the blood flow can't get out very well. This naturally will cause a brain pressure increase. The elevation of intracranial pressure inside a confined channel which is housing the brain will end up changing brain function and it will cause neurological problems. That's one problem she had. Unfortunately, she also developed a second problem which often is associated with venous occlusion: that is dural AV fistula.
From a practicality standpoint, many people thought the occlusion was the first problem, but later on it was found to be artery and vein shunting. So, dural AV fistula is one of the things that somehow wrongly connects into the outflow channel of the brain. Naturally these structures are not connected but now they're connected because of a venous channel occlusion. So the blood outflow tried to find a way out and ended up connecting to certain channels, but these channels turned out to be arteries so now they were merged. The artery ended up creating a short circuit into the vein which was supposed to drain the blood from the brain. Now, she's got a secondary problem. Outflow is already very limited; it's already a traffic jam. Suddenly she's pumping a lot of a high pressure flow from the artery directly into a low-flow system. Now, the entire outflow system ends up further pressurized and these veins end up further compromising the blood flow from the brain. She's getting a double whammy. She went from being a straight "A" student to having trouble academically. Even with a tutor helping her, she was having tremendous trouble trying to understand. That was probably two months prior to this final event.
Did other doctors not know what was going on or not know how to fix it?
Dr. P. Roc Chen: Unfortunately, it is extremely difficult to interpret sometimes and sometimes we, even as a parent, think that it's just kids changing their behavior or maybe a learning disability. So it wasn't well picked up until the last moment, but I also have seen some adults' diagnosed with early Alzheimer's who had similar problems.
So you looked at it and then you came up with an innovative way to try to help her out. Can you talk about that?
Dr. P. Roc Chen: By the time she got to us she was in a coma, so that was the final tipping point. She was at the critical standpoint; she had the potential to die from this. Then we ordered an imaging study which suggested that she had two conditions: we mentioned the dural AV fistula and also the venous sinus occlusion. We were unable to change whatever occluded the blood vessel, meaning that she still had to use a limited outflow channel. Similar to eight lanes of traffic driving through a one-lane street, but with a significantly pressurized system which was coming from the dural AV fistula, we knew her situation was extremely difficult but we believed it could be fixed. If we could fix that, we could at least return the venous channel's pressure down to a near-normal state. So we reversed brain connections and hoped that would most likely return her brain function back to normal. There are two ways to do this treatment, in general. One is through surgery. Basically you open the skull, find the millions of wrong connections, then you coagulate it and cut it, but in Lauren's situation, her brain was extremely swollen with a lot of short-circuited flow. That meant that she faced the high likelihood of intraprocedure bleeding and the surgical risk would be quite high.
So she could have bled to death if you did surgery on her?
Dr. P. Roc Chen: That could be one issue. Secondly, if the brain is swollen it makes surgery extremely difficult and the surgical risk increases significantly. So the second way to do it is to use a catheter, meaning an endovascular technique, to find a way to navigate through certain blood vessel channels to get to the point where you can try to block the wrong connections. The way to block it is to use a certain liquid material. There are old materials available but now we have a newer technique using material that is similar to that, but has much better control: this Onyx "glue." The way you inject it is to inject directly into the affected area and then watch as the liquid quickly solidifies and seals the entire blockage. Once sealed, we would be able to restore entire venous pressure. So that was the plan.
So what did you seal to make it work again?
Dr. P. Roc Chen: The DAVF (dural arteriovenous fistula), which basically blocks the venous outflow. Once you disconnect it, you reverse the entire outflow state. So even though she's living with a limited outflow venous channel, she is much better off than when she had the continuously high pressure blood pumping into it. So that was the whole idea. A difficult part with her case was that her wrong connection, the dural AV fistula, was extremely diffused. Number two: because her outflow channel was almost completely cut off, it made it nearly impossible to access from a conventional route, to get to the point where we could try to seal those abnormal short circuits. So these were two difficult points that made this case much more troublesome. But in the end, we were able to find a way to navigate through the tiny arteries and use those tiny arteries to get to where we needed to go.
Can you use this on other people now?
Dr. P. Roc Chen: Yes. We're using this same material for many patients who have a similar condition and arteriovenous malformations. Even in different concentrations, for short periods of time, they used it for brain aneurysm treatments, although the popularity has decreased recently. We also use it to reduce blood flow in cranial tumors prior to surgery to reduce surgical complications.
For more information, please contact:
P. Roc Chen, MD, FACS, FAANS
Cerebrovascular/Endovascular Neurosurgeon
Mischer Neuroscience Institute
(713) 704-7100