Posts Tagged ‘electrodes’

This is a follow-up to my blog called Enduring the first long-term EEG . . .   Read on if you want to know what life is like when your child is first diagnosed with epilepsy.  In my previous post I described my son’s first long-term video EEG and some of the frustrations we faced.

From 2002 until 2005 my son had  six short-term EEG’s and seven or eight long-term video EEG’s at four different clinics/hospitals, which included two of the leading clinics in the nation. We have done so many of them that I have lost count.  When my son first had seizures I was totally ignorant about the tests and how it was all done.  The following is a description of what happens for a short-term EEG.  We have had lots of experience with this and I thought it would be a good idea to share some of it for those that are just beginning their investigation of seizures.

Based on our experience the procedure for putting on the electrodes for an EEG are pretty consistent from clinic to clinic. In the first step the technician measures the patient’s head to correctly position each  electrode.  In the earlier days, they put marks on the head using what looked like a blue grease pencil. The pencil hurt and my son hated it. After about three years, at another clinic they actually used an EEG cap that had all of the electrodes on it and it was just a matter of getting it positioned correctly. More recently the clinics got smart and started using washable markers.  What a difference this made for my son.

The electrodes are placed on the head based on the  international 10–20 system which ensures that the naming of electrodes is consistent across laboratories.  For each electrode the EEG technician  does the following steps:

    • scrub the area with an abrasive soap to get rid of any dead skin cells.  Dead skin cells can diminish the effectiveness of the electrode.  The technician does this scrubbing using a Q-tip except the stick is wooden.  This was another aspect of the EEG that my son hated, because he said it hurt.
    • fill an electrode with a conductive pink gel or paste.  Each electrode consists of a small, tin cup which is connected to the wires.  The conductive gel is scooped into the cup of the electrode.
    • place the cupped portion of the electrode onto the marking on the head
    • soak a small swatch of gauze in glue.  The glue was another trigger for my son to become anxious and at times became hysterical.  It got to the point that all the technician had to do was bring out the brown bottle and my son would cry.
    • place the glue-soak gauze over the top of the electrode cup and onto the head.  The purpose of this is to keep the electrode in place.
    • connect the end of the electrode wire to an apparatus that tells the technician if they are getting a good reading.  The goal is to make all of the lights red.  If the reading is not good, the technician will use an instrument that looks like a hypodermic needle (which isn’t) to squirt more of the conductive gel under the electrode cup.  This instrument is also another aspect of the EEG that may make a child anxious.  It is not that it hurt; it is just that it looks like a shot needle and they are scared.

This whole process is started all over with the next electrode.  As you can see this is a laborious task and takes some time.  In most clinics there are 19 recording electrodes used, plus a ground and a system reference placed behind the ear and on the chest.  On a good day this process takes 40 minutes to one hour.  Now add to it the time it takes to get your child to calm down and endure the process.  This isn’t easy because they need to sit perfectly still.  Typically my son wanted to get up and run away.  After our first EEG we knew to bring in toys or food to distract him while the electrodes were put on.

With a short-term EEG the patient remains in a room on a bed.  The technician then goes through the steps of the EEG. The goal is to induce normal and abnormal EEG activity.  It isn’t always necessary to trigger an actual seizure because sometimes the EEG will show patterns that denotes  a seizure.  The technician guides the patient through a few tests while the EEG is capturing the brain activity.  These procedures were consistent for every clinic that we went to.  These tests include:

    • asking some simple questions for a response
    • opening and closing the eyes
    • hyperventilating by blowing on a pin wheel for about five minutes.  Over all of my son’s EEG’s he was never able to do this for five minutes.  This is one test that I had to really coax him to do it and keep doing it.
    • looking at a strobe light which is set to different frequencies
    • sleeping for a half hour.  This is also somewhat tricky.  Several of the clinics we went to did the tests early in the morning and had the parent get the child up in the night so that they are sleep deprived.  Sleep deprivation in some cases can trigger a seizure.  In addition this procedures helps your child fall asleep during that portion of the test.

Once all of brain activity is captured via the EEG, the technician helps take off all of the electrodes.  They use a special solvent that takes off most of the glue and electrodes.  Afterwards they wash the hair and scalp in an attempt to get all of the glue and gook off.  The first time my son had an EEG using glue his hair was long.  He has tight, curly hair and it was a nightmare trying to get all of the glue out.  Luckily he is a boy and we learned to cut his hair short which made it easy to get everything off.  One technician remarked that short hair is not necessarily the best, because the shortness of the hair can push against the electrode and reduce the effectiveness of the test.

That’s the end of the test and at this point all you have to do is wait.  Typically you have to wait for the results. There are a couple of things to keep in mind.

  • An EEG measures the brain waves on the surface of the brain.  If there are issues deeper than that they may not be detected on the EEG.
  • An EEG is not conclusive because there are so many factors that can influence it
  • The capture of the brain waves may be affected by “noise” during the EEG.  Noise is defined as other brain activity that may interfere with the results of the EEG.  Types of “noise” include:
    • Eye-induced artifacts (includes eye blinks, eye movements and extra-ocular muscle activity)
    • ECG (cardiac) artifacts
    • EMG (muscle activation)
    • Glossokinetic artifacts (tongue)

Recently, independent component analysis techniques have been used to correct or remove EEG contaminates.  These techniques attempt to “unmix” the EEG signals into some number of underlying components.

These artifacts were one of the major problems we had in diagnosing my son.  It took almost five years to confidently diagnose his seizures.  The reason it was so hard is because most of his daily seizures were facial oriented, with most activity associated with his eyes.  His seizures began with a tug at the right eye and then eye blinking, or eye fluttering, and sometimes head and body jerks.  Since these were eye focused it was difficult to differentiate the seizure movements from normal blinking movement.

In the beginning there was a lot of debate about what these events were.  My son’s videos of his events were looked at from doctors all over the country.  They were also reviewed at a symposium for practitioners who specialized in movements disorders, including tics.  The reviews also ended inconclusive.

The other factor to consider is whether your neurologist is a specialist in epilepsy and ideally an epitologist who is a neurologist that has specific training for diagnosing and treating epilepsy.  In our case it was an epitologist who was able to review the EEG results and eliminate the “noise” artifacts.  She also saw in some of the videos that my son struck a “fencing” position which is a particular type of movement with epilepsy.

It was Mayo Clinic that did a test that measures the speed the eye blinking during my son’s seizures.  Typically tics are mimicable and would have a speed that was equal to a normal eye blink.  The test showed that these blinks were considerably faster than a normal blink, which is what I had been saying for years.

The other thing to keep in mind is that there may be more than one thing going on at the same time.  This is the case with my son.  We have determined that he has movements that are a part of his epilepsy, movements that are associated with non-epileptic seizures, and movements associated with Tourette Syndrome.  It is interesting that earlier in our investigation tics were considered, and it is highly possible that he was having both seizures and tics.

Probably the best advice I can give you is follow your instincts.  When we were struggling to figure out what was going on with my son, I did a lot of research.  In those days the internet was not that prominent, both from quality of content and for user-friendly interfaces.  Instead I bought thousands of dollars of books, including text books.  I studied topics including epilepsy, movement disorders, non-epileptic seizures, myoclonic seizures and much more.  All during this time, my instinct told me that my son was having seizures.  I taught myself everything I could about the brain and neurological disorders.  I kept talking to doctors, learning more and more as I continued my research.

Persistence has paid off.  The neurologist determined that the source of my son’s seizures was the left frontal part of the brain and his latest seizures are classified as myoclonic seizures.  Between having a vagal nerve stimulator (VNS) and anti-epileptic drugs the majority of my son’s epileptic seizures are gone.  Rather than happening twenty times a day, he may have one seizure every other week or so.

I hope this post was helpful.  In the near future I will be writing a post about long-term video EEG.  Come back to my blog for more stories about the medical challenges my family have face.

To Be Continued . . .

This is a follow-up to my blog called Facing the antiepileptic drugs   Read on if you want to know what life is like when your child is first diagnosed with epilepsy.  In my previous post I described Benign Rolandic Epilepsy as a diagnosis for my son.  

My son was continuing to have multiple seizures on a daily basis.  Before we got back to the neurologist my son had a larger seizure, still not as big as the first one, but I this one was more like  a flutter seizure.  My son was having the same movements with the eye tugs,  but they were rapidly happening and then he fell backwards.  It lasted less than a minute, but it was also obvious he was not cognitive when it occurred.  So now we had seen 3 different types of seizures including:  a tonic clonic seizure (previously known as grand mal seizure), the eye tugging/blinking with head jerks, and these eye fluttering events.

We went  back to the neurologist office.  We discussed  how my son’s personality had changed and the medication Tegretol.  The neurologist said we will define a plan to wean him off the Tegretol.  We also discussed that there was no reduction in seizures and that new types were appearing.  The neurologist decided we should do a long-term non-invasive video electroencephalogram (EEG).  He also said we could start reducing his tegretol medication while this EEG was being done.

As a side note my husband had finally returned from his trip overseas.  He was somewhat shocked when he saw what was happening to our son even though I had described everything in our phone conversations.  I had to spend some time to get him caught up on all of the information that I had learned or that the doctors had reported.  This was a really important task because my husband comes from a culture that still has an old perspective of epilepsy which is tied to a spiritual beliefs.  My goal was not to dissuade his beliefs but instead add the biological, medical perspective.  I have found through our years of marriage it is not good to force a change of thinking and instead lead my partner to a new perspective on his own terms.

Once again we were in a waiting mode.  For this EEG we needed to be admitted to the hospital and the neurologist said we should expect to stay 3 – 5 days.  There was a waiting period for getting admitted to the hospital because there is a limited number of beds on an EEG unit.  Lucky for us our appointment was in a week.  I knew very little about an EEG but soon got first hand knowledge.  Here is a brief definition of an EEG:

An electroencephalogram (EEG) is a painless procedure that uses small, flat metal discs (electrodes) attached to your scalp to detect electrical activity in your brain. Your brain cells communicate via electrical impulses and are active all the time, even when you’re asleep. This activity shows up as wavy lines on an EEG recording.  An EEG is one of the main diagnostic tests for epilepsy. An EEG may also play a role in diagnosing other brain disorders.

This sounded okay, and didn’t appear to be a thing to worry about.  The description was similar to the short-term EEG which we had already done.  The only difference was the longer duration.

Finally the day came and we took our son to the Children’s Hospital associated with our neurologist.  My son was admitted and then we were led to the epilepsy monitoring wing.  We met the technician who was going to get my son prepared for the EEG by placing the electrodes on his head.  This hospital did not call them electrodes and instead referred to them as “buttons.”  The reason they did this was to not raise anxiety or misunderstanding in the child.  The word electrodes could sometimes conjure up images of electricity and children become afraid that the electrodes were going to hurt them.

The first step was to provide a detailed description of what the three types of seizures looked like.  The technician was very patient and took his time explaining to my son what he was doing.  He began to measure my son’s  head with a measuring tape and then marked his scalp with a special pencil, to indicate where to attach the electrodes.  This pencil became my son’s bane.  He hated the sensation and began to cry.  As this was going on I thought to myself why is it necessary for using this type of pencil.  It was ineffective and the technician would have to put repeated strokes on the marking place to get it to leave a mark.  This is an age of erasable markers.  I wondered why they didn’t use them.  (A few years later at a different hospital my son had another long-term video EEG and they used markers instead of these grease pencils.  This was a big relief to us.)  I believe this measuring / marking process continued for about 26 locations on the scalp.

Next the technician started using a something similar to a Q-tip but more sturdy and began scrubbing each spot with a gritty cream with the intention of improving the quality of the EEG recording.  The grease pencil was bad but this scrubbing step was even worse.  My son cried.  We had to take numerous breaks to get him calmed down.  He was only 3 1/2 years old and begged for them to stop.  I had to do everything I could to comfort him and get him through this process.  It wrenched my heart.  He was really terrified.  Finally all the spots had been scrubbed.

The next step was to put the “buttons” on.  The technician brought out the brown bottle of special adhesive which basically smelled like airplane glue.  Each electrode was connected to a wire which eventually would be connected to a device that amplifies the brain waves and records them on a computer.  This process consisted of the technician taking a small amount of pink gel, putting it on the electrode, taking a small piece of gauze, dipping it in the glue, placing the electrode on a specific spot of my son’s head and then covering it with the gauze with the glue.  This continued for all 26 electrodes.

Occasionally the technician would test the signals from the electrode and if they didn’t meet a certain standard for this testing device the technician would use an instrument to rub the skin beneath the electrode.   In some cases if the electrode did not have a good signal they used this device to squirt more pink gel under the electrode.  The unfortunate thing is this device looked like a syringe.  Even though the technician showed my son that it was not a needle my son was still scared.  He wanted to run away and begged me to help him.  They also put two more sensors on his chest for measuring heart rate and pulse.  Finally they wrapped all of these wires together, like a giant braid, and then wrapped my son’s whole head with gauze with the intention of preventing him from picking at the electrodes.

For this first long-term video EEG, this process took almost four hours.  The process would not normally take four hours but the timing depended on how well the child tolerated the process.  By the time we were done my son was wore out and hungry.

The technician led us to my son’s hospital room and plugged the wires into the EEG device.  He showed us where the camera was and that it was important to stay in view of this camera, which meant staying on the bed.  I knew this was going to be the hard part.  Keeping a 3 1/2 year old sitting in once place for a long time is really difficult.  The camera captures body motions while the EEG simultaneously records your brain waves during a seizure. This helps the neurologist pinpoint the location in your brain where seizures begin.

The hospital had some toys and videos to entertain the children.  I knew that my son would be more comfortable with some of his own toys so I told my husband to go home and bring back some of my son’s toys.

The technician also showed me a button that I should push if I noticed a seizure.  This would then mark the recording of the EEG for them to evaluate.  The technician then wanted to take a baseline for the test and ran through the same tests that they do in a short-term EEG such as opening and closing my son’s eyes, asking him some questions, blowing at a pin wheel for several minutes to trigger hyperventilation, and then looking at some flashing strobe lights.

Once the technician completed all of the instructions all we had to do was wait.  And wait.  And wait.

To be continued . . .

Specific information about the EEG was provided by Mayo Clinic at: