Normally, the brain's nerve cells (neurons) communicate with one another by firing tiny electric signals that pass from cell to cell. The firing pattern of these electric signals reflects how busy the brain is. The location of these signals indicates what the brain is doing, such as thinking, seeing, feeling, hearing, controlling the movement of muscles, etc. A seizure occurs when the firing pattern of the brain's electric signals suddenly becomes very abnormal and unusually intense, either in an isolated area of the brain or throughout the brain.
If the whole brain is involved, the electrical disturbance is called a generalized seizure. This type of seizure used to be called a grand mal seizure. The most easily recognizable symptom of a generalized seizure is the body stiffness and jerking limbs known as tonic-clonic motor activity.
To continue reading this article, you must login
Subscribe to Harvard Health Online for immediate access to health news and information from Harvard Medical School.