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Glossary

 

Temporal Lobe

brain sectionsclick to enlarge photograph

The temporal lobe, as the name implies, is located near the temples, just below the center of the cerebrum. This area of the brain is responsible for language and memory, as well as speech and auditory perception.

Thalamus

brain sectionsclick to enlarge photograph

The thalamus is a structure in the inner brain, located at the top of the brain stem. The thalamus is responsible for receiving sensory information (except smell) and relaying it to the rest of the brain.

Tonic Seizures

Tonic seizures are generalized seizures characterized by prolonged contraction of the large muscle groups involved in posture, as well as stiffening of the limbs. In contrast to many seizure types, tonic seizures do not produce rhythmic convulsions. They usually occur shortly before or after waking and usually involve most of the brain, typically resulting in a loss of consciousness.

Tonic-Clonic Seizures

Tonic-clonic seizures (formerly known as grand mal seizures) are the type most people imagine when they think about epilepsy, and they are a common type of seizure in children. These convulsive generalized seizures typically begin with a cry or sound caused by air being forced from the lungs, then progress to the tonic phase, which often involves a fall to the floor, stiffening of the limbs, clenching of teeth, and rolling back of the eyes. The tonic phase, which rarely lasts more than 30 seconds, is followed by the clonic phase, which presents itself as the rapid, rhythmic jerking of the limbs and torso. This phase is also characterized by shallow breathing, a bluish appearance to the skin, and loss of bladder and/or bowel control. The clonic phase typically lasts for a few minutes before it gradually begins to slow and eventually stops. After the seizure, individuals are typically difficult to rouse and, if awakened, will be sleepy and confused.

Tuberous Sclerosis Complex (TSC)

Tuberous sclerosis complex (TSC) is a genetic disorder that can affect most major organs, including the brain, and causes seizures in approximately 80 percent of patients. Approximately one-third of children with TSC experience infantile spasms.

Uncus

The uncus is a structure of the brain located in the mesial, or middle, of the temporal lobe. The uncus functions in processing smells.

Vagus Nerve Stimulator (VNS)

The vagus nerve stimulator (VNS) is a therapy used to treat seizures. This technique relies on a pacemaker-like device that is implanted under the skin of the chest and supplies intermittent electrical impulses to the vagus nerve as it passes through the neck. The vagus nerve is a cranial nerve within the autonomic nervous system that influences motor functions in the larynx, diaphragm, stomach, and heart. Intermittent stimulation of this nerve with low-intensity electrical impulses may reduce seizures in some people. This therapy is most often used in conjunction with medications.

Video Electroencephalogram (vEEG)

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. See also Electroencephalogram.

WADA Test

The WADA test is typically performed before seizure surgery on the temporal lobe to test the temporal lobe functions of language and memory. During the WADA test, doctors put each half of the brain to sleep for a few minutes. This allows a neuropsychologist to test the language and memory functioning of each side of the temporal lobe in isolation. The results of the test show doctors how much of the language and memory functions are located in the right and left sides of the brain, and are used to determine how much of the temporal lobe can be removed. The Wada test is named after the neurologist Juhn A. Wada, MD, who first performed the test.

West Syndrome

West syndrome is a neurological disorder of infancy and early childhood, characterized by the presence of three features: a highly chaotic EEG pattern known as hypsarrhythmia, a type of seizure called infantile spasms, and mental retardation.

Working Memory

Working memory is the ability to not only access information previously acquired, but also to make generalizations about this information and apply it to other types of situations. By accessing this prior knowledge, an individual acquires a deeper understanding by discovering how the original information fits within the context of other knowledge.

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This content was last reviewed on November 20, 2006.