Massachusetts General Hospital

Home | About This Site | Site Map | Glossary | Video Index



Déjà Vu

Déjà vu is a French phrase that translates as "already seen." Déjà vu refers to a sensation or feeling that something being experienced for the first time has actually happened before. Déjà vu is a frequent type of aura for temporal lobe seizures.


neuronclick to enlarge photograph

Dendrites are branchlike projections through which nerve cells receive signals.

Deoxyribonucleic Acid (DNA)

Deoxyribonucleic acid (DNA) is made up of molecules that encode all the instructions necessary for a living organism to grow. Two long strands of DNA make up the familiar double helix shape.


A dietitian is a medical professional who specializes in diet and metabolism. A dietitian who is knowledgeable about epilepsy and has had specialized training in administering the ketogenic diet and other dietary therapies can instruct patients on how to implement these treatments.

Doose Syndrome or Myoclonic-Astatic Epilepsy (MAE)

Doose syndrome, also called myoclonic-astatic epilepsy (MAE), is an epilepsy syndrome that typically arises in children between the ages of one and five years. The seizures that result are generalized, and there is no known cause for this syndrome. In addition, seizures associated with Doose syndrome are often resistant to anticonvulsant medications, and other treatment options are often considered. Children with Doose syndrome typically experience mixed seizure types.

Drop Attack

A drop attack is a seizure that causes an individual to suddenly fall to the ground. Although many seizure types can cause drop attacks, they are most commonly associated with atonic seizures during which a child experiences a sudden loss of all muscle tone. Also referred to as drop seizure.

Early Intervention

Early Intervention programs vary from state to state, but are generally designed to provide services for infants and young children who are at risk for developmental delays. Services include occupational, speech, and physical therapy.

Educational Psychologist

An educational psychologist is a licensed psychologist who evaluates children with learning difficulties and advises educators and parents on the child's development and educational progress.

EEG Technologist

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.

Electrical Status Epilepticus of Sleep (ESES)

Electrical status epilepticus of sleep (ESES) is near-constant epileptiform activity during as much as 80 percent of sleep in the form of continuous spike and slow wave discharges. ESES is associated with childhood syndromes involving cognitive dysfunction and epilepsy, such as Landau-Kleffner syndrome.

Electrocorticography (EcoG)

Electrocorticography (EcoG) is a diagnostic test in which an electrode is placed onto the brain to record electrical activity. The test is performed in the operating room, typically during epilepsy surgery, and may show or confirm where in the brain seizures are coming from. The procedure is also used to define eloquent cortex, or regions of sensory function such as the areas of the brain that control motor function and speech. This is done by stimulating various parts of the brain with electrical current and then monitoring the effect in the body. Also known as brain mapping.

Electroencephalogram (EEG)

normal EEGclick to enlarge photograph

An electroencephalogram (EEG) is a noninvasive diagnostic test used to measure and record the electrical activity of the brain. An EEG is used to help locate the origins of seizures and help diagnose epilepsy.


Encephalitis is a brain inflammation often caused by a viral infection. Encephalitis can cause seizures.


Epilepsy, sometimes called "seizure disorder," is a neurological condition that manifests itself as a susceptibility to seizures. Individuals diagnosed with epilepsy have typically experienced two or more seizures as a result of factors other than preventable conditions, such as fever or low blood sugar levels, which can cause seizures but are not necessarily indicative of epilepsy.

Epilepsy Syndrome

An epilepsy syndrome is defined by patterns of recurrent seizures that follow a similar course from one individual to the next, including age of onset, seizure type, and, often, characteristic EEG patterns. Importantly, individuals with a particular epilepsy syndrome also respond in a predictable manner to medications, and such syndromes may relate to underlying genetic factors and point to a family history of or predisposition to this form of epilepsy.

Epilepsy syndromes are sometimes grouped into two classes: benign and catastrophic. Seizures associated with benign syndromes are typically well controlled with medications and are often outgrown. In contrast, seizures associated with catastrophic syndromes often persist despite medication or the age of the child, and typically result in more extensive developmental problems.


An epileptiform change is a pattern on an electroencephalogram (EEG) that shows abnormal electrical activity in the form of spike waves, sharp waves, and slow waves, which may be suggestive of seizures.


Epileptogenic means to cause seizures or epilepsy.


An epileptologist is a neurologist who specializes in treating epilepsy.


Etiology is the cause of a disease or disorder.


Excitation refers to the processes through which brain electrical activity is increased, causing nerve cells to fire. Healthy brain function relies on a balance of excitation and inhibition of nerve cells. Seizures are thought to occur when there is too much excitation, or too little inhibition, in the nerve cells of the brain.

Executive Functioning

Executive functioning, or executive control, describes the processes of developing and applying systematic approaches to solving problems and challenges. This is one of the most complex functions that our brains perform. It involves planning, self-regulation, and the ability to think flexibly or creatively. This allows us to consider more than one option, choose one, and then create a plan of action based on past experience, rather than acting on impulse or emotion.


Extensor refers to muscles that are involved in straightening or extending the joints in the body.

Febrile Seizure

A febrile seizure is a seizure that occurs in young children during rapid elevation of temperature. Febrile seizures are common in children under five years of age, often run in families, and are not considered epilepsy.


Flexor refers to muscles that are involved in bending the joints in the body.


The focus is the place in the brain from which the seizure originates. Foci refers to more than one place of seizure origin.

Frontal Lobe

brain sectionsclick to enlarge photograph

The frontal lobe makes up the largest portion of the cerebrum. Located just behind the forehead, this area of the brain is responsible for emotions, personality, memory, and skills associated with executive functioning, including problem solving, planning, and self regulation. The frontal lobe also includes the motor strip, which controls muscles in the limbs and face.

Functional Magnetic Resonance Imaging (fMRI)

Functional MRI is a noninvasive procedure that uses a special magnetic resonance imaging scanner to look at blood flow in the brain to determine which areas of the brain are activated during such physical activities as seeing, hearing, and touching.

Back to Top


This content was last reviewed on November 20, 2006.