Generalized tonic-clonic seizures

Generalized tonic-clonic (GTC) seizures (formerly called grand mal seizures) usually are not difficult to diagnose. The loss of consciousness usually occurs simultaneously with the onset of a generalized stiffening of flexor or extensor muscles (the tonic phase). After the tonic phase, generalized jerking of the muscles (clonic activity) occurs. A GTC seizure is almost always followed by deep postictal sleep.

Some patients may have a simple partial seizure (aura) preceding the loss of consciousness. This indicates that the onset of the seizure is located in a limited area. As the seizure spreads in the cortex, the seizure develops into a GTC seizure. This type of seizure is classified as a simple partial seizure with secondary generalization.

Two types of episodes that may end with brief generalized tonic-clonic seizures should not be treated with antiepileptic drugs:

• breath-holding attacks in toddlers
• syncope in both children and adults

Adapted from: Holmes GL. Classification of seizures and the epilepsies. In: Schachter SC, Schomer DL, eds. The comprehensive evaluation and treatment of epilepsy. San Diego, CA: Academic Press; 1997. p. 1-36.
With permission from Elsevier (www.elsevier.com)
Reviewed and revised January 2004 by Gregory L. Holmes, MD, Dartmouth Medical School