a disorder of the nervous system, characterized either by mild, episodic loss of
attention or sleepiness or by severe convulsions with loss of consciousness.
epilepsy, a chronic
disorder of cerebral function characterized by periodic convulsive seizures.
There are many conditions that have epileptic seizures. Sudden discharge of
excess electrical activity, which can be either generalized (involving many
areas of cells in the brain) or focal, also known as partial (involving one area
of cells in the brain), initiates the epileptic seizure. Generalized seizures
are classified as tonic-clonic (grand mal), in which there is loss of
consciousness and involuntary contraction of all the muscles of the body,
lasting a few minutes; or absence (petit mal), in which there is clouding of the
consciousness for about 1 to 30 sec and no falling, with as many as 100 attacks
occurring daily. Partial seizures include Jacksonian epilepsy, characterized by
jerking in the hand and face on the side opposite the brain activity; and
psychomotor seizures, in which there may be localized convulsion with no loss of
consciousness, as well as incoherent speech and various involuntary movements of
the body. Often these are accompanied by a warning cluster of signs and symptoms
called an aura.
The cause is unknown in over half the cases of
epilepsy, especially in those with onset under age 20. Predisposing factors in
other cases include familial history, head injury, alcohol withdrawal,
infections (such as meningitis), and abnormalities (such as tumors) of the