New onset seizures are common, with epilepsy being the fourth most common neurological disorder. An epileptic seizure is defined as a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain. The location of this neuronal activity in the brain helps to define the clinical manifestations that can be quite variable.
The condition of epilepsy is a disorder of the brain characterized by an enduring predisposition to generate epileptic seizures. It is important to recognize that not all epileptic seizures indicate the presence of epilepsy, but everyone with epilepsy has epileptic seizures.
It is very important when evaluating new-onset seizures that a thoughtful and thorough approach is used in evaluating what happened to make a proper diagnosis and not to mislabel individuals. Epilepsy is a potentially lifelong disorder that may require lifelong medication management; there is also some significant safety issues as well as stigma.
In many cases, an evaluation may be triggered following a loss of consciousness with or without “shaking.” Less often, individuals may be noticed having episodes of confusion, staring or loss of time and the clinical symptoms are much more subtle. In these cases, symptoms may persist for a longer period of time before presenting for evaluation simply based on the subtlety of the symptoms. Regardless of the clinical presentation, once the individual presents to a neurologist, it is very important to have a structured approach to evaluation and management.
I do like to separate “treatment” from “management.” Treatment may be provided by an emergency department, with the person being prescribed an antiseizure drug with recommended follow-up. Management involves a more comprehensive approach to the person (not just a “patient”) considering age, gender, education/work, family planning and financial situation, among other things. What follows is my approach for the evaluation of new-onset seizures in adults that I have developed over the last two decades in an active clinical practice that we use to provide appropriate management.
After taking a very thorough history – hopefully with a witness for the person’s clinical episodes, as the individual affected is typically unlikely to be able to report any significant details – and reviewing any available laboratory or imaging data, I will typically try to cover the answers to three important questions: What happened? Why did it happen now? What are the chances of it happening again?
What happened? The first and most important question to answer is whether the patient had an epileptic seizure or something else. The clinical description of the person’s symptoms leading up to the event, during the event and immediately following the event are the most important in trying to make this determination. If the person can describe what they were feeling prior to, during and following the event, and there is a reliable witness who is able to accurately describe what they witnessed, it is sometimes an open and shut case.
It is important to differentiate symptoms that would be more typical for presyncope from a typical seizure aura as well as whether the person has a typical postictal state versus some other type of symptoms. In many cases, there is no witness for the actual event itself, so it becomes necessary to make some presumptions.
All too often a differentiation between syncope and an epileptic seizure is made simply on the basis on whether urinary incontinence or tongue biting occurred. In reality, either of these can occur with syncope or a seizure, so it should not be used as a standard for differentiating them from one another.
What can be helpful, if the person did bite their tongue, is asking them where. It is more common to bite the sides of the tongue with an epileptic seizure and the tip of the tongue with syncope. Ultimately, being able to answer this first question is up to the quality of the history obtained and whether appropriate testing, including brain imaging and at least a routine EEG, has been completed. The impact of these test results on the diagnosis and prognosis will be discussed in greater detail later.
It is important during this discussion to differentiate between provocation (something that can cause a seizure, such as an abrupt high fever in young children, concussion, drug or alcohol withdrawal, etc.) and triggers (something that can bring out a pre-existing tendency to have a seizure, such as sleep deprivation, a moderate fever, moderate alcohol use/ intoxication, etc.). Provoked seizures do not predict a significant risk of future seizures whereas triggered seizures do.
For the remainder of this discussion, we are going to stipulate that the patient did have an unprovoked epileptic seizure, and that leads us to the next question.
Why did it happen now? The better question to ask is “why not now?” When it comes to epileptic seizures, it is well accepted that there is no point in the human lifespan that there is no risk for developing new onset seizures and epilepsy.
It is generally well accepted that about 10% of the population will have at least one seizure in their lifetime, but only about 10% of those, or between 1% and 4%, will go on to have recurrent seizures, and therefore a diagnosis of epilepsy.
From a statistical perspective, there is a higher risk of presenting with epilepsy in the first year of life and over the age of 55. In the first year of life, this is most typically related to infections, perinatal events, congenital malformations and genetic predisposition. In the older population, new onset seizures are most often associated with cerebrovascular disease/stroke, brain tumors and neurodegenerative disorders.
There is a small bump in the 15– to 24-year-old population, when some genetic epilepsies can still present but that can also be an increased risk associated with high-risk behaviors such as increasing alcohol and drug use or head injuries associated with sports or other activities.
It is common that a person who presents with new onset seizures wants to know exactly why it happened, but in most cases, we will not be able to find a specific reason. That is very frustrating, but it is the reality of this condition.
What is the chance it is going to happen again? This can be the most difficult question to answer, especially if we are not exactly sure of the diagnosis. In many situations we do not have a very clear description of events, which can make it much more difficult to prognosticate future risk. Even when it is clear that the event was an epileptic seizure and it is the first ever, it can be very difficult to differentiate whether this is their “first” or their “one.” (Remember, about 10% of the population will have at least one seizure in their lifetime, but only about 10% of those, or between 1% and 4%, will go on to have recurrent seizures.)
If a person has already had at least two clinical episodes, and you are fairly certain that they were epileptic seizures based on the clinical description, it is more likely than not that they will have recurrent seizures if not properly managed. These patients have met the classic definition of epilepsy and have about a 90% chance of recurrence without treatment.
In other situations, it will depend on test results and some of the more subtle clinical features of the patient’s described event. If the patient has appropriately abnormal testing, with a structural lesion on the MRI that can be associated with epileptic seizures and/or an epileptiform abnormality on their EEG, they can have up to a 60% chance of recurrence without appropriate management.
These individuals also meet the definition of epilepsy based on the updated 2014 International League Against Epilepsy definition of epilepsy. If the patient has only had one episode, and testing is unrevealing, the risk of recurrence can vary between 18% and 25%. They may fall into the higher range of that risk if the clinical episode had symptoms suggestive of focal onset, their episode came out of sleep or if they have had some prior brain insult that puts them into a higher-risk category, such as a stroke, prior traumatic brain injury, etc.
Following a detailed review of these three questions, it is appropriate to discuss the patient’s approximate risk of recurrence without treatment. In my practice, if the risk exceeds 50% (including those individuals who have had two or more clinical events already, or for those individuals who diagnostic testing suggests have a higher risk of recurrence), I very strongly recommend initiation of an antiseizure drug. For those that do not fall into one of these categories, following a detailed discussion of their potential risk of recurrence (18% to 25%), as well as the implications of recurrent seizures – which includes a potentially significant risk of morbidity and mortality as well as restrictions placed on driving and possibly work-related activities – I will leave it up to the person.
It comes down to a question of how much risk are they willing to take? It is important to be very clear that even when starting an antiseizure drug, there is never a guarantee that seizures will not recur. This is a very unfortunate reality in the management of epilepsy as there is no test available to predict the efficacy of any given antiseizure drug at any given dosage. It is literally trial and error. Once treatment is initiated, the only way to know that more medication is necessary is for seizures to recur. Therefore, it is very important to discuss the risks of recurrent seizures with all patients, regardless of whether they are being treated or not.
Choice of specific antiseizure drugs is beyond the scope of this article. The good news in 2022 is that there is a wide range of safe and effective antiseizure drugs to choose from. For those with inadequate insurance who do not have good financial resources, several of these medicines can be quite inexpensive and others have very generous support from their manufacturers.
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Dr. Lawrence Seiden
Dr. Seiden is a neurologist at the MS Center of Atlanta. Following a 2-year fellowship at the University of Maryland in Clinical Neurophysiology and Epilepsy, he remained on faculty at the University of Maryland Epilepsy Center where he was director of the Epilepsy Monitoring Unit. He is a fellow of the American Epilepsy Society and serves as chair of the professional advisory board of the Epilepsy Foundation of Georgia.