A First Look at Seizures and Epilepsy
A seizure is caused by an abnormal and excessive discharge of electrical activity in the brain usually accompanied by a change in behavior, sensation, or consciousness. Seizures can originate from many different sources and occur in various locations within the brain. Epilepsy is defined as the occurrence of two or more seizures that are not brought on by preventable causes, such as fever or low blood sugar. As simple as this definition is, the process of diagnosing epilepsy can be very complex due to the variation in seizure types and their severity. Many types of seizures are so subtle that they may go unnoticed, appearing, for example, to be simple lapses of attention. Other seizure events may be attributed to disorders unrelated to abnormal electrical activity in the brain, such as psychiatric problems.
Distinguishing between seizures and episodes that are not seizures is the first task of diagnosis because it guides the specific course of treatment. This can sometimes be difficult given the wide range of medical, neurological, and psychiatric disorders that present symptoms resembling specific seizure types. These include fainting, sleep-related behaviors, movement disorders, daydreaming, breath holding, tics, panic attacks, and events called pseudoseizures, or nonepileptic events, which result from subconscious mental activity.
For more about seizure types, see the Seizure Types and Syndromes section of this site.
Diagnosing epilepsy relies on a variety of tools, techniques, and observations. Some of these are sophisticated technologies that enable physicians to identify abnormalities in brain structure or function. Although these tools are integral to the process of epilepsy diagnosis today, some of the most important diagnostic information comes to doctors from patients and their families.
Eyewitness Accounts and Family Histories
Observations of the events, behaviors, and movements that lead up to, accompany, and follow a possible seizure are critical in determining whether or not the event is a seizure and, if so, the specific seizure type. Such firsthand accounts provide the foundation for nearly all epilepsy diagnoses and help physicians, patients, and families determine the best treatment options going forward.
Because physicians seldom witness their patients' seizures, they must try to learn as much information as possible from those who have experienced or observed them. This is where the partnership between doctor, patient, and parent is forged. Teachers and schools play a role in this process as well.
Physicians typically ask individuals and their families a series of detailed questions about a seizure episode and the events leading up to it. Below are some of the questions that a physician might ask:
- When did the episode happen?
- What was the child doing at the time?
- Was the child sick or overly tired, or did the child have a high fever?
- Were there any other unusual events that may have provoked the seizure?
- Did the child's behavior change in any way prior to seizure onset?
- How did the seizure start, and what was the child doing during the seizure?
- Did his/her eyes move to one side?
- Did his/her head turn to one side?
- Did the child become stiff or limp during the episode?
- How long did the seizure last?
- Did the child lose continence of bowel or bladder?
- Was the child tired or confused following the seizure?
- Did his/her extremities appear weak following the seizure?
The particular list of questions a physician poses following a child's seizure will often vary from one case to the next. If a child has had more than one seizure, a physician will often attempt to identify a pattern to the child's seizures with regard to events that precede the seizures and how the seizures play out.
Physicians encourage those who have witnessed a seizure to write down all details about the event, before their memory of that event fades. Physicians also recommend that parents videotape seizures if possible. These videos help doctors identify subtleties that other observers might miss and thereby improve the prospect of an accurate diagnosis.
For more information about the role videotaped seizures and eyewitness accounts play in the diagnosis of epilepsy and particular seizure types, see the Brain Interactive.
Single vs. Recurrent Seizures
The diagnosis of a single seizure would seem to suggest a potential course of evaluation and treatment. However, one seizure does not lead to a diagnosis of epilepsy, nor does it necessarily indicate any immediate course of treatment. In practice, doctors often do not treat a single seizure because approximately 60 to 70 percent of individuals who have one seizure will never have a second. Even so, doctors often obtain an EEG after a child's first seizure and recommend that parents watch a child for signs of recurrence. In some specific situations in which the risk of recurrence after a single seizure is thought to be higher than normal, physicians may begin epilepsy treatment immediately, rather than waiting for a second seizure to occur.
For children who experience recurrent seizures, the diagnostic and treatment protocol is aimed at providing complete seizure control. Recurrent seizures can undermine normal brain development, especially in infants and children, so they need prompt attention. Importantly, certain types of anticonvulsant medications and other treatments are most effective on particular seizure types. What's more, some types of medications, if not matched properly to an individual's seizure type, can actually make seizures worse. This makes accurate diagnosis a critical step both in epilepsy treatment and in the prevention of developmental delays.
To learn more about specific seizure types, see the Seizure Types and Syndromes section.
To learn more about effective treatments for epilepsy, see the Treatment section.
Eyewitness accounts of seizure events provide information that is critical to developing an accurate diagnosis. In conjunction with this, physicians also use a number of sophisticated technologies to better understand brain structure and function in an individual with epilepsy. The most important and commonly used tools are the electroencephalogram (EEG), computed tomography (CT) scans, and magnetic resonance imaging (MRI).
The EEG is a safe and painless procedure that provides direct evidence of abnormalities associated with epilepsy. The procedure records electrical fluctuations in the brain over time via electrodes placed on the scalp. These electrodes are connected by wires to an EEG machine that displays the brain's electrical activity as a series of wiggly lines known as traces.
Doctors and EEG technologists are trained to observe the brain's electrical activity and differentiate between normal and abnormal patterns. Patterns characteristic of epilepsy are called epileptiform changes. These patterns, which are commonly observed during periods between seizures in individuals with epilepsy, are most often represented as spikes, sharp waves, and spike-and-wave discharges (see images at right). Although most seizure types can be seen as abnormal patterns on the EEG, it is important to know that some people with epilepsy show normal EEG patterns because their seizures arise from regions deep within the brain.
Focal spikes and sharp waves are characteristic of partial seizures, whereas spike-and-wave discharges occurring diffusely across a larger portion of the brain are suggestive of generalized seizures. By assessing these patterns, doctors can in most cases identify specific seizure types and can locate the seizure origin, or focus, in partial seizures. This information helps the physician to identify an appropriate course of treatment.
The video EEG provides simultaneous recording of video and electrical activity in the brain. This enables physicians to relate any abnormal electrical patterns to any physical manifestations that a seizure might cause. This can help physicians identify the seizure focus, estimate seizure frequency, and differentiate seizures from nonepileptic events.
Computed Tomography (CT)
Like x-rays, CT scans use small amounts of radiation to create an image of the internal structures of the brain. CT scans help doctors identify brain abnormalities commonly associated with seizures. These include tumors, atrophy (decrease in brain size), scar tissue, and abnormal blood vessels or brain structures. CT scans are typically more readily available than are magnetic resonance imaging scans. The technique is also faster and easier to use in many cases and so can be important in emergency situations.
Magnetic Resonance Imaging (MRI)
MRI produces images of the internal structures of the brain with far more detail than CT scans reveal. MRI is particularly important in identifying brain abnormalities that are small or only subtly different from normal tissue. These include small tumors, malformed brain regions, abnormal blood vessels, small amounts of scar tissue, and mild atrophy. Because of the high-resolution images they produce, MRI scans are considered the "gold standard" in imaging technology. However, they are not readily available at all hospitals.
Other Diagnostic Tools
Physicians may use a variety of other technologies to more precisely locate the origin of seizures, particularly if the seizures are not easily treatable with medication and if a surgical treatment is being considered. Single photon emission spectroscopy (SPECT) and positron emission tomography (PET) measure changes in blood flow and metabolic rate in brain tissue and help physicians to identify areas of neuronal dysfunction; magnetic resonance spectroscopy (MRS) provides functional and biochemical information that can be used in conjunction with structural imaging; and magnetoencephalogram (MEG) technology records electromagnetic changes in the brain, providing another way to assess brain activity.
It Is Important to Remember
- Early diagnosis and treatment can make a tremendous difference in the developmental outcome for a child with epilepsy.
- Accurate diagnosis of an individual's seizure type is critical to identifying an appropriate course of treatment.
- Seizure diagnosis can be a complex process.
- Sixty to seventy percent of people who have one seizure never experience a second seizure.
- The occurrence of two or more seizures not caused by a preventable condition, such as fever or low blood sugar, defines the diagnosis of epilepsy.
- Patients and families often provide a great deal of firsthand information that can help physicians more accurately diagnose cases of epilepsy and particular seizure types.
- In some cases, diagnostic tests can help pinpoint where in the brain a seizure originates, leading to more precise treatment options.
- Even though seizures have varied precursors and manifestations, the person living with epilepsy, with the help of family, can learn to identify his or her own particular seizure pattern.
An EEG technologist is a person who administers the EEG test and who is trained to recognize the abnormal patterns that are characteristic of epileptic seizures.
A neurologist and a pediatric neurologist are physicians who care for people affected by disorders of the nervous system. An epileptologist is a neurologist or a pediatric neurologist who specializes in the treatment of epilepsy.
A neuroradiologist is a physician who interprets images, including x-rays, ultrasounds, CT scans, and MRIs of the central nervous system, including the brain. A neuroradiologist is trained to recognize abnormalities in brain structure.
A neurosurgeon is a surgeon who specializes in performing surgery on the nervous system, including the brain. A neurosurgeon who treats people with epilepsy is trained in the identification and resection (surgical removal) of brain regions where seizures originate. These neurosurgeons are often also qualified to treat epilepsy with implants such as the vagus nerve stimulator (VNS).