What Are the Steps We Take in Making a Diagnosis of Seizure?

1)Take a Detailed History.  We want to know what your seizure looked like to people nearby. What did you feel just before the seizure?  Were you aware of what was going on?  How long it lasted?  Where you confused for a prolonged period of time afterwards or did you quickly return to normal awareness?  What new medications or substances did you take that day?  Were you sick or ill before or after the seizure, or were you in good health at the time?  Did you lose control of your bowel or bladder function during the seizure? Did you bite your tongue or cheek? Have you had anything like this before?  Do you have any family members with seizures?

2)Lab Tests.  We will send lab tests based on what we learn from the history.  There are no particular lab tests that have proven helpful to making the diagnosis of seizure in a person who appears to be in good health. 

3)Electroencephalogram (EEG).  This safe and easy to perform test will measure your “brainwaves”, or the electrical activity created when you brain cells send signals to each other.  We will gently place recording electrodes (small flat metal discs) on your scalp.  This is not painful at all.  Once these discs are in place you will lay down on a bed and the test will begin.  We may ask you to hyperventilate, breath quickly, for a few minutes or we may flash a light into your eyes during the test.   These do not hurt.  For the rest of the procedure, which usually lasts about 20 minutes, you are encouraged to fall asleep if possible.   We often do between one and three of these EEG sessions.  The number of these tests we order on you depends on the doctor’s judgment.   It is important to remember that usually this test cannot prove that the episode you experienced was NOT a seizure.  It’s common for people who develop the syndrome of Epilepsy to have normal EEGs.  This test can only measure the electrical activity from the outermost portion of the brain, and so misses large parts of the brain.  So a normal EEG is often not very helpful in determining if the episode you had was a seizure or not.  On the other hand an “abnormal” EEG, can be helpful in suggesting that the episode you experienced was a seizure after all. 

4)Brain Imaging with Computerized Tomography (CT) or Magnetic Resonance Imaging (MRI).   The first point to make when discussing brain imaging is that the majority of people having either one seizure or multiple seizures over their lifetime have a normal looking brain.  Only a small percentage of people have something that we can see on these imaging techniques that is related to or the cause of their seizures.  Less than ten percent of people having a seizure will have a brain tumor, an infection, or other abnormality seen on the MRI or CT.  We feel that everyone having their first seizure should have either of these tests, the CT or the MRI so that we can identify, and treat, that small group of people with a potential life threatening cause of their seizures.   If your CT or MRI is normal, this is good news.   In many of these people with a normal CT or MRI, the abnormality causing the seizures is usually microscopic, well beyond the resolution of these scans to detect. 

Common Questions about the Diagnosis or Treatment of Seizures

What Causes a Seizure?

In the majority of people having a seizure, there is an abnormality in their brain cells on a microscopic level that causes these cells to occasionally develop an unusual firing pattern.  The abnormality may be in many cells in the brain or just in a few.  Sometimes, these cells will alter their firing pattern causing either part or all of the brain’s other cells to begin firing in an abnormal way.  This brain activity can manifest itself as impaired awareness and or alterations in your body movements.  These episodes of abnormal brain activity usually last just a few minutes.  After this abnormal brain activity stops, it is very common to feel extreme fatigue or confusion for several minutes or hours afterwards.   In a few people, the seizures are caused by either short-term or long-term damage to the brain, a brain tumor, reaction to a mediation or infection.   In these cases, the seizures may be caused by small clusters of damaged brain cells like after a head injury, or by widespread but short lasting dysfunction such as in a drug overdose.  It is important to remember that the majority of people having seizures don’t have a history of these problems, and they appear otherwise normal.

What Is the Difference Between Seizures and Epilepsy?

A seizure is the name of the event where the abnormal brain activity causes an alteration in your awareness and or your behavior and movements.   Epilepsy is a condition where a person has had one or more seizures in the past and is expected to probably have more in the future.  It is important to realize that only about thirty percent of otherwise normal people having one seizure go on to develop Epilepsy.  The majority of people who have normal testing will not have another seizure.   Most people who have one seizure are not Epileptics.   To make the terminology even more complicated,  you may notice that the term Seizure Disorder and Epilepsy are used interchangeably.

My Electroencephalogram (EEG) is Normal.  Does That Mean I Didn’t Have a Seizure?

No.  There are many people with Epilepsy who have normal looking EEGs.  As we discussed in the section about testing, the EEG can only measure part of the brain.  As well, these brain cells that develop an abnormal firing pattern are not firing like this every minute of the day.   Sometimes we can see some of this abnormal brain activity at a time when you feel otherwise normal, and in some people this activity is so frequent that we can capture it on a twenty minute EEG.  In some other people though, the abnormal activity is either hidden from our view or occurs so rarely that we’re unlikely to capture the activity on an EEG, even if you were attached to the EEG machine for several days. 

My Computerized Tomography (CT) or Magnetic Resonance Imaging (MRI) is Normal. 

Does that Mean I Didn’t Have a Seizure?

No.  But you can relax a little.  As we mentioned in the section on Testing, the purpose of doing the imaging test is to identify the minority of people with a brain tumor, infection or other non-microscopic brain abnormality responsible for the seizure.   The majority of people having a seizure have problems with their brain on a microscopic level.  These imaging tests are not microscopes.  Rather they allow us to look at the brain as if we peeled away the skin and bone.  We cannot see brain cells with our naked eyes, so we cannot see them on the MRI or CT.  We cannot see any abnormalities in the brain much smaller than a one millimeter or so, and individual brain cells are much small than this.

How Does the Doctor Predict Whether I’m Going to Have Another Seizure?

This is one of the most common questions.  We use the story you told us in the initial interview and the tests we’ve run to help give you a prediction whether you are likely to experience seizures in the future.   Unfortunately doctors cannot absolutely predict when or even if you will have another seizure.   What we can do is to give you a feel for what your risk is of having future seizures.    Here are some common scenarios we may present to you. 

One seizure and a normal workup:  After five years approximately thirty percent (30%) of people in this category had at least one more seizure. 

One seizure and an abnormal EEG:  In five years about fifty percent (50%) of people in this category had at least one more seizure.

If you’ve already had two or three seizures, even if the testing is normal:  After five years over seventy percent  (70%) of people in this group had at least one more seizure.    As you noticed, the most predictive characteristic of your chance of having another seizure is having had more than one seizure already. 

Those people with an infection, brain tumor, or reaction to a medication as the cause of their seizures do not fit into these categories.  These numbers above are only for those people who appeared to be normal, without any clear cause for their seizures.

How Can You Be Sure the Episode I Experienced Was a Seizure?

Sometimes we are lucky enough to capture a seizure on the EEG machine, though this is fairly rare.  Most often we have to put together the details that you tell us during the initial history taking.  On occasion the EEG or MRI can help us, but often we have to rely completely on the history.  For most people their seizures will be stereotyped.  Meaning that most of the episodes will look or feel almost the same.  There are times when we are not sure that it was a seizure after the first event, but later on after these events recur it becomes easier to make the diagnosis.  

Can Other Things Besides Seizures Cause What I Experienced?

Yes in some cases.  In listening to the history, the doctor will be listening for clues as to the nature of your episode.   Sometimes a decrease in blood flow to the brain, caused by a heart problem or just transient low blood pressure can cause a loss of consciousness and occasionally some twitching.  Panic attacks or hyperventilation can cause events that look somewhat seizure like.   There are also psychological events called pseudoseizures that arise from the subconscious and look just like seizures.  There are some other more rare medical conditions that can be confused with seizures.   This is why the initial history taking is so important.

Do I Have to Take Medication?

Once you and your doctor feel confident what you experienced was a seizure, it is time to begin discussing whether it is worthwhile for you to take medications to prevent seizures in the future.  Most often if you’ve only had one seizure and your workup with CT or MRI and EEG are normal, then most doctors will suggest not taking medication.  If you remember the previous question on predicting seizures, those people who have one seizure and a normal workup have only a 30% risk of another seizure in five years.  Likewise if your seizure was caused by some short lasting illness or a reaction to a medication, it may not be necessary to take a medication to prevent future seizures.  Usually most people consider taking medications when they’ve had more than one seizure or if there is strong evidence from the EEG, MRI or other testing that even though they’ve had only one seizure, its likely that they will have another.

What Can I Expect from Seizure Medications?

When starting your first anti-seizure medication about fifty percent of people taking seizure medications will have complete seizure freedom.  That means over the course of a year they will have no seizures.  There will be another group of people who have a meaningful reduction in the number of seizures, and lastly a small group of people who will continue to have seizures without any reduction in frequency.  For this last group who don’t seem to respond to the medication, it may be necessary to try a different medication or try two medications at the same time.  In the beginning, most anti-seizure medications have some noticeable side effects.  Most often there is mild sedation or sleepiness.  This often improves over a few weeks, and many times after this initial period is no longer a problem.  Its important that you read the patient information on the medication prescribed to you so that you can be aware of the possible side effects.  One important but rare side effect of all the anti-seizure medications is a slight increased risk of suicidal thoughts or suicidal acts.  This seems to effect less than one percent (1%) of people taking these medications.   This is a small number of people, but since it is such a serious potential side effect, if you notice that you’ve become more depressed or having suicidal thoughts after starting one of these medications, let your doctor know. 

What about Driving and Other Activities?

Every state has driving restrictions for people having seizures.  Most of the states have a three to twelve month waiting period after your last seizure before you can drive again.  If you are seizure free for the duration of this time period, most states will allow you to drive again.  If your seizure was clearly caused by some extraordinary circumstance such that we predict that it is highly unlikely for you to another seizure, like a reaction to a new medication or a medical illness that was cured or corrected, then you will probably not have to stop driving.  Though if you’ve had a seizure and we cannot predict with great certainty that it will NOT occur again, then you’ll be restricted from driving.  Here is Washington state there is a six month waiting period after your last seizure before you can drive again.  If you go the entire six months without having a seizure, then it is most likely that you can return to driving.  Though if you have a seizure within this time, you’ll have to mark the six months from the time of the latest seizure.   If you were taking seizure medication for part or all of the six months, were seizure free on medication, but then decided to stop taking your medication, you’ll have to start the six month period over from the time you stopped the medication.  This applies to people who have been taking seizure medication for many years and now want to stop taking their medication.  Because its possible that the only reason they’ve been seizure free is due to the medication, they will have to prove that they can remain seizure free for six months off medication before driving. 

Where Can I Go for More Information

www.epilepsyfoundation.org

http://www.ninds.nih.gov/disorders/epilepsy/epilepsy.htm

other links are on the seizures main page