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Find terms and definitions to help you understand epilepsy.


Absence seizure: is a type of seizure that causes a brief loss of consciousness (also known as “dialeptic seizure” or as “petit mal seizure”, which is the older term describing absence seizures). During an absence seizure, the patient typically interrupts his/her activity, and appears to stare blankly. Rarely, there may be some eye blinking or other minor movements of the mouth and hands.

Absence seizures are more common in children (who may have a condition known as “childhood absence epilepsy”). Unlike generalized tonic-clonic seizures (“grand mal seizures”) absence seizures are often very brief (5 to 20 seconds), and may occur multiple times each day. Children with absence seizures may be mistakenly thought to be “daydreamers” in school. A significant number of children with absence seizures (up to 50-70%) may “outgrow” their seizures by late adolescence.

Adverse effect: side effect; negative, unwanted effect from a medication or other therapeutic intervention

Ambulatory EEG monitoring: a system for recording the electroencephalogram outside the hospital for prolonged periods of time (24 hours or longer, up to 3 to 4 days). This system gives the patient the capability to walk around and carry on normally, while EEG recordings are being made. EEG electrodes are connected to a special recorder that is slightly larger than a portable cassette player. The recorder can be strapped onto the patient’s waist, with the wire running either under or outside of his/her shirt.

Americans with Disabilities Act: a comprehensive civil rights law that makes discrimination against people with disabilities illegal; the act applies to employment, access to public places, and places of accommodation.

Amygdala: an almond shaped deep structure of the brain located by the hippocampus on the underside of the temporal lobe. Its main function is to take in the information from the environment, assess its emotional importance, and arrange a proper response.

Anticonvulsant: an anti-seizure medication used to control both convulsive and nonconvulsive seizures (usually referred to as “antiepileptic drug”).

Aseptic meningitis: irritation of the covering of the brain and spinal cord caused by blood or blood byproducts, usually treated with steroids, not antibiotics.

Atonic seizure: a type of seizure, that causes a sudden loss of muscle tone, particularly in the arms and legs; this seizure type often causes the patient to fall (“epileptic fall”).

Aura: a warning, which is usually the first symptom, that occurs at the beginning of a seizure; the aura refers to a subjective experience by the patient, and is not visible to observers. The type of symptom experienced depends upon the part of the brain that is affected first. Some of the typical auras include, episodes of “déjà-vu” (a sense that one has been in a certain situation before), epigastric auras (an uncomfortable abdominal sensation of “rising” numbness or tingling), unexplained tastes or odors or sometimes even a “hard to describe feeling”. Auras usually occur in patients with focal epilepsy, although not all patients with focal epilepsy experience auras. (Auras may occur in isolation, or progress to become a stronger focal or a “full-blown” convulsive seizure).


Basal ganglia: these are deep brain structures involved in movement. They are a relay station for impulses between the higher functioning part of the brain (cortex) and the brain stem.

Brain stem: this structure lies between the brain and the spinal cord and is critical for the transmission of impulses between the two parts of the nervous system. It holds many vital centers, including breathing and cardiovascular.

Brand-name drug: a medication manufactured by a major pharmaceutical company, and marketed under a proprietary, trademark-protected name. (Brand-name drugs are often expensive, but tend to be uniform in the amount of drug and the method of preparation).

Breath Holding Spell: is a pediatric condition that is usually seen in toddlers. Breath holding spells occur in response to a minor injury, or as an emotional response when a toddler gets upset and cries. During an episode the child cries out and then appears to hold his/her breath. The child’s lips and mucous membranes may appear bluish (“cyanotic breath holding spell”) or less commonly, a child may appear very pale (“pallid breath holding spell”) during the episode. If the episode is quite prolonged, it may result in a generalized convulsion. It is important to distinguish such a convulsion from epileptic seizures. Consultation with the primary care provider is the first step, and if necessary further subspecialty consultation with a neurologist may be obtained for accurate diagnosis.


Clonic seizure: a seizure type that consists of repetitive, rhythmic jerks involving all or part of the body.

Complex partial seizure: a seizure type that includes impairment of awareness, for example, patients seem to be "out of it" or "staring into space" (Automatisms or other purposeless or semi-purposeful movements, such as lip smacking, chewing, swallowing, picking at own clothes or other objects are frequently seen as part of this seizure type, which is also known as “automotor seizure”).

Patients are usually unaware of their surroundings and unable to interact during a seizure. Such seizures may result in confusion, combativeness or wandering about, putting patients at risk for sustaining injuries. It is therefore important for observers to maintain a cool and calm demeanor during a patient’s complex partial seizure, while preventing the patient from experiencing any harm.

Corpus callosotomy: an operation that cuts (transects) the corpus callosum, in order to interrupt the spread of seizures from one hemisphere of the brain to the other. (Callosotomies may be complete, or involve only a portion of the corpus callosum. Although seizures generally do not completely stop after this procedure, they usually become less severe).

Corpus callosum: a band of nerve fibers located deep in the brain that connects the two halves (hemispheres) of the brain. (The corpus callosum helps the two hemispheres communicate and share information).


Electrode: a conductive disk (usually metallic) attached to the scalp. Each EEG electrode conveys the electrical activity of the brain, through a wire, to an EEG recording machine (During a typical EEG recording 21 electrodes are temporarily pasted to the patient’s scalp).

Electroencephalogram (EEG): a diagnostic test that measures human brainwaves, the electrical impulses in the cerebral cortex. (This test helps a physician in making the diagnosis of epilepsy).

Epilepsy: a chronic medical condition marked by recurrent, unprovoked epileptic seizures. (Many individuals may experience a single, or more, seizure(s) as a result of fever, medicine withdrawal, electrolyte changes etc., but these individuals are not diagnosed as having epilepsy, if seizures do not recur spontaneously). It is therefore important to understand that the terms “seizure” and “epilepsy” are not synonymous and should not be used interchangeably.

Epilepsy surgery: a neurosurgical procedure that aims to eliminate the patient’s seizures; this is usually accomplished by removing (resecting) the epileptogenic zone. (This approach is successful in eliminating seizures in a large majority of patients, depending on the type and location of the patient’s epilepsy, as identified during video-EEG monitoring).

Epileptogenic zone: the region of the brain responsible for the abnormal electrical signals that cause seizures. (When the entire epileptogenic zone is removed during epilepsy surgery, patients are free of seizures after surgery).

Extratemporal cortical resection: an operation that aims to cut out (resect) brain tissue, which contains the seizure focus, and is located in an area outside the temporal lobe. (The term “extratemporal” simply means that the abnormal epileptic tissue is located in an area of the brain other than the temporal lobe, most often in the frontal lobe; less commonly the abnormal tissue is located in the parietal or occipital lobe).


Febrile seizure: a seizure associated with high fever in infants and children, typically seen from the age of 3 months up to 5 years, which results from abnormal electrical activity in the nerve cells of the brain brought on by the child’s fever. A febrile seizure usually manifests as tonic-clonic convulsion (and is therefore also known as a “febrile convulsion”). The exact cause of febrile seizures is not known. Seizures may occur when the child's temperature rises or falls rapidly. Febrile seizures are usually benign, and not a cause for concern.

Frontal lobe: the largest part of the brain, extending from the forehead to behind the ear. It controls movement on the opposite side of the body. This lobe also plays a role in complex thinking, controlling behavior, and speech production.


Generalized epilepsy: the patient’s epilepsy results from electrical impulses that are generated and recorded simultaneously throughout the entire brain, as opposed to “focal epilepsy” (also known as “partial epilepsy”, the other broad category of epilepsy), the abnormal electrical impulses are generated and recorded (at least initially) in a relatively small part of the brain. The part of the brain generating the seizures is sometimes called the “seizure focus” (also known as “epileptic focus”).

Generalized seizure: a seizure type that involves the entire brain (both sides of the brain) at the same time.

Generalized tonic-clonic seizure: is the type of seizure most people think of, when they hear about seizures (also known as “generalized convulsion”, or as “grand mal seizure”, which is the older term describing generalized tonic-clonic seizures). Although their duration may seem very long, most generalized tonic-clonic seizures last less than 2 minutes. During these seizures, the patient loses consciousness, and exhibits stiffening and contraction of all body muscles. The patient may give out a loud cry, and may briefly stop breathing and/or exhibit labored respirations. Stiffening of body muscles is then followed by jerking of these muscles, which gradually slows down and stops, leaving the patient in an exhausted, difficult-to-awake state, which lasts for several minutes. This state of exhaustion is referred to as the “post-ictal state”.

Generalized tonic-clonic seizures are physically violent, and may result in falls and/or seizure-related injuries. If you are witnessing such an event, it is important to lay the patient on a flat surface and place the patient on his/her side. Do not attempt to open a seizing person’s mouth, as this is more likely to injure you or the patient, or result in dangerous aspiration of objects into the patient’s lungs. A common myth about “grand mal seizures” is that the patient may “swallow their tongue." This never occurs.

Generic drug: a drug that is not sold under a proprietary, trademark-protected name (“brand-name”), but is chemically identical to the corresponding brand-name drug. The “Food and Drug Administration” (FDA) requires that all generic medications undergo rigorous testing to prove they are equivalent to the brand name drug with regards to dosage, safety, strength, how they are taken, quality, performance, and intended use – for example, carbamazepine can be obtained as a generic drug or as Tegretol or Carbatrol, its brand names.

Generic drugs are usually less expensive, because their manufacturers do not have to offset the investment costs incurred by the developer of the new drug. Although research is still limited, it appears that generic versions of many antiepileptic medications can be used safely and effectively for most individuals with epilepsy. At the same time concerns exist in the treatment of epilepsy, as the FDA allows for a certain range of variability – even though generic drugs must be equivalent to their brand counterpart. These equivalence standards may not be appropriate for all classes of antiepileptic medicines, for all types of epilepsy, and for all patient populations. At this time, generic substitution in epilepsy remains a controversial issue; such treatment decisions need to be individualized, and discussed in detail with the treating physician.


Hemianopsia: loss of vision in one half of the person’s visual fields.

Hemimegalencephaly: one hemisphere is much larger and overdeveloped as compared to the other.

Hemiparesis: severe or complete weakness of one side of the body.

Hemisphere: one half of the cerebrum (encephalon), which is the largest part of the human brain (also known as “cerebral hemisphere”).

Hemispherectomy: a surgical procedure, which aims to remove one cerebral hemisphere (one side of the brain), also known as “anatomic hemispherectomy”. The operation is often modified to remove only a portion of the hemisphere, disconnect the remaining portions, and split the corpus callosum – a procedure that is known as “functional hemispherectomy”. (This latter procedure interrupts the communication among the various lobes of the abnormal, epileptic hemisphere, as well as the communication between the two hemispheres of the brain).

Hippocampus: this is a crescent-shaped structure by the amygdala on the underside of the temporal lobe. It extends to the lateral ventricle. The main role of the hippocampus is in memory, with its primary responsibility being the formation of new memories. It is also involved in learning.

Hydrocephalus: increased fluid in the brain cavities either from increased production or a blockage in the fluid pathways. This usually causes increased pressure, resulting in headaches, changes in mental status, sleepiness, nausea, and/or vomiting.

Hyperventilation: is the state of breathing faster and/or deeper than necessary (over-breathing). Patients may be asked to hyperventilate for a few minutes during their EEG recording, to increase the chances of finding epileptic or other abnormal EEG activities.


Ictal: refers to the period during which the seizure (“ictus”) occurs – as opposed to the period in-between seizures, which is known as “interictal period”.


Ketogenic diet: a high-fat, low-carbohydrate diet used to treat seizures in some children, whose seizures are difficult to control with medications. The diet is called “ketogenic”, because it results in the generation of “ketones” (also known as “ketone bodies”) that are products of a fat burning metabolism. By maintaining a metabolic state similar to that of starvation or fasting, the diet works by changing how the brain obtains its energy to function. Instead of getting energy from sugar, the brain will get energy from fat breakdown.

Precisely how this helps to control seizures is not known. (Seizures often lessen or disappear during periods of fasting. The diet is very high in fat and low in carbohydrates, and is most often recommended for children ages 2 through 12, who have seizures that are difficult-to-control with medications. The diet has also been recommended for children with certain mitochondrial/metabolic disorders). An important requirement for beginning the diet is a commitment from those, who will be taking care of the child, as the diet requires extra time and effort.


Lesionectomy: surgery to remove an isolated brain lesion (such as a tumor or vascular malformation) that is responsible for generating the patient’s seizure activity.

Lobe: one of the four sections/subdivisions of each cerebral hemisphere. The cerebrum, which is the largest part of the brain, is subdivided into four paired sections: frontal, temporal, parietal, occipital. In focal epilepsies the seizure focus is usually located in one of these four lobes.

Lumbar puncture: a diagnostic procedure during which the fluid surrounding the spinal cord (cerebrospinal fluid) is withdrawn through a needle and examined in the laboratory (also known as “spinal tap”).


Magnetoencephalography (MEG): a diagnostic test that measures the brain's magnetic activity, which is generated by the brain’s electrical activity (in the cerebral cortex).

Malformation of cortical development: a broad term representing an abnormality present from birth that involves most of one side of the brain.

Multiple subpial transections: is a palliative surgical procedure aimed to decrease seizures, which begin from areas of the brain that cannot be safely removed, such as areas that control movements or language (The surgeon makes a series of shallow cuts “transections” within the brain tissue to interrupt the spread of seizure impulses).

Myoclonic seizure: a seizure type that consists of sporadic jerks, usually on both sides of the body. Patients sometimes describe the jerks as brief electrical shock-like movements. (Intense myoclonic seizures may cause the patient to drop or involuntarily throw objects).


Neurologist: a physician who specializes in the treatment of disorders of the nervous system (such as epilepsy, which is a disorder of the brain)

Neuron: a single nerve cell (The human brain is made up of billions of neurons. Many neurons malfunctioning together are necessary to produce a seizure).

Non-epileptic event: an event that resembles a seizure, but is actually produced by another condition, such as Tourette syndrome (and other movement disorders), and heart rhythm disturbances (so-called arrhythmias). Certain psychological conditions can also bring on a non-epileptic event (the so-called “psychogenic non-epileptic seizures”).


Occipital lobe: this part of the brain lies at the back of the skull. It is essential to vision.


Parietal lobe: this lobe extends from the frontal lobe back to the occipital lobe. It is the part of the brain that processes sensory information. It allows a person to understand what he is touching, tasting, smelling, as well as pain and temperature.

Partial seizure: a type of seizure that occurs in a limited area, in only one hemisphere of the brain (and is therefore also known as a “focal seizure”). Partial seizures represent one of the most common types of seizures, and are more amenable to treatment with epilepsy surgery, as compared to the so-called generalized seizures. Partial seizures most often originate from the temporal lobe. However, they can also begin from the frontal lobe, or the occipital or parietal lobes. If they spread to involve a large enough area of the brain, partial seizures can turn into a generalized tonic-clonic seizure (so-called “secondarily generalized tonic-clonic seizures”). So, it is possible for a patient to have both types of seizures (i.e. both partial and secondarily generalized seizures).

Perinatal infarction: a stroke that occurs around the time of birth.

Psychogenic non-epileptic seizure: a seizure-like reaction that may sometimes occur in response to stress or unfavorable events in a patient’s past or present life (these episodes are also known as “non-epileptic behavioral events”, or as “pseudo-seizures”, a less-preferred term that has been used in the past to describe this condition). Psychogenic non-epileptic seizures or behavioral events are often mistaken for epileptic seizures, but they are not due to underlying epilepsy. During an attack, the patient often exhibits shaking of the limbs and body as seen in epileptic seizures, and he or she may become unresponsive. A consultation with a neurologist is often necessary, in order to determine whether a patient’s symptoms are due to epilepsy or to an underlying psychological disorder. Observation of the seizures in the inpatient video-EEG-monitoring unit may be necessary to make a definitive diagnosis.


Rasmussen’s encephalitis: a rare neurological condition that presents with seizures, loss of motor skills and speech, weakness on one side of the body, and mental deterioration.


Seizure: a sudden episode of altered brain function caused by an abnormal and excessive electrical activity in the brain. (Most seizures cause sudden changes in behavior and/or motor function).

Seizure focus: the area of the brain that gives origin to the patient’s seizure.

Simple partial seizure: An epileptic seizure that involves only a part of the brain in one hemisphere, and is not associated with impairment of consciousness.

Staring spells due to inattention: Staring spells due to inattention (also known as “staring spells of non-epileptic origin” are commonly misdiagnosed as “absence seizures”. Both absence seizures and “staring spells due to inattention” may outwardly appear very similar. Both are associated with brief episodes of a blank stare, and lack of awareness for the surroundings. In order to prevent a misdiagnosis of epilepsy, and mistreatment with prolonged use of antiepileptic medications a consultation with a neurologist and EEG or video-EEG testing may be necessary.

Status epilepticus: a prolonged seizure lasting for several minutes* or a series of repeated seizures without regaining consciousness in between, resulting in a continuous state of seizure activity. Status epilepticus is a medical emergency, and can be life-threatening; medical help should be obtained immediately in this setting! (*Traditionally a duration of 30 minutes or longer has been used to define status epilepticus, although it is important to remember that treatment should be started as soon as possible, and certainly before 30 minutes have gone by).

Sturge-Weber disease: a congenital disease characterized by a facial birthmark (“port wine stain”) and neurological abnormalities caused by an excessive growth of blood vessels. The side of the brain involved is the same side as the port wine stain.

Syncope: is the medical term for “fainting”, a sudden and brief loss of consciousness, during which the patient may fall down, and from which recovery is spontaneous. Sudden emotional stress, severe pain, sudden standing up, or prolonged standing are some of the common causes, which may lead to syncope. Prior to syncope patients may feel dizzy or light-headed, feel their heart racing and/or have cold sweating. Things may start to look dimmer and blurry, and then all of a sudden the person appears to “black out”. Distinguishing syncope from seizure can sometimes be difficult. Misdiagnosis with epileptic seizures may occur if there is no clear history of a precipitating cause. On the other hand, although infrequent, some epileptic seizures may have syncope as one of their manifestations. The primary care provider may refer such patients to the neurologist for consultation, and specialized testing if needed (testing may include a “tilt table test” and continuous “video-EEG monitoring” to help establish the correct diagnosis).


Temporal lobe: this part of the brain lies above the ear. This lobe helps a person understand speech and plays a role in memory. It is also concerned with hearing. Some nerve fibers that are part of the visual system starting in the occipital lobe pass through the temporal lobe and help a person with space and depth perception along with understanding distance.

Temporal lobe resection: a surgical procedure during which brain tissue in the temporal lobe is cut away (resected) to remove the seizure focus, which is located within the temporal lobe (the most common surgical procedure in the temporal lobe is called “anterior temporal lobectomy”).

Thalamus: this is a deep brain structure concerned with relaying sensory and motor impulses between the brain and the rest of the nervous system. It creates much of the background electrical activity seen on an EEG. The thalamus works with the brain stem to maintain consciousness.

Tilt-table test: is a test used to determine the cause of unexplained syncope or fainting spells. This test (also known as “head upright tilt test”) involves being tilted, always with the head-up, at different angles for a period of time (2 minutes at 30 degrees, then 2 minutes at 45 degrees, then up to 45 minutes at 70 degrees). Heart rhythm, blood pressure and other symptoms are closely monitored and evaluated with changes in position. This test allows doctors to evaluate the patient's cardiovascular response to these changes in body position.

Tonic seizure: a seizure type that is characterized by stiffening of the muscles, which is sustained for more than a few seconds.

Tonic-clonic seizure: a seizure type that is characterized by stiffening, and then jerking of the muscles. (This sequence of muscle contraction is the hallmark of the “generalized tonic-clonic seizure”, which used to be called “grand mal seizure”).


Vagus nerve: is the longest of twelve paired cranial nerves, which connects the lower part of the brain to various organs in the mouth, chest and abdomen. The left and right vagus nerves belong to the so-called “autonomic nervous system”, the part of the nervous system responsible for controlling body functions that are not under voluntary control, such as the heart rate and the motility of the gut. (Each vagus nerve participates in the motor function of the voice box, diaphragm, gullet, stomach, gut and heart, and the sensory function of the ears, and tongue, among other organs).

Vagus nerve stimulation (VNS): a less invasive surgical treatment for epilepsy involving implantation of an electrode in the patient’s neck, which delivers electrical stimulation to the segment of the vagus nerve located in the neck. On the other end the electrode is connected to a pacemaker, which is placed under the skin in the patient’s chest. There is no physical involvement of the brain in this surgery, and the patient cannot generally feel these electrical pulses. The VNS device sends regular, mild pulses of electrical energy to various areas of the brain via the vagus nerve. (VNS is usually programmed to cycle on and off continuously, however the patient or a caretaker can turn the stimulator on – when the patients feels that a seizure is coming on – by swiping a small magnet over the pacemaker, so-called “on-demand activation”).

Video-EEG monitoring: continuous simultaneous recording of EEG (the patient’s brainwaves) and video (the patient’s behavior associated with these brainwaves). This technique (which is also known as “EEG-video monitoring”) is carried out at comprehensive epilepsy centers and aims to diagnose epilepsy and localize the seizure focus. The results are useful to determine appropriate (medical or surgical) therapy.