Medical Definition of tonic–clonic
: relating to, marked by, or being a seizure that affects both cerebral hemispheres and is characterized by the abrupt loss of consciousness with initially tonic muscle contractions followed by clonic muscle spasms During a generalized tonic-clonic seizure, also known as a grand mal seizure, the person might have a vocal outburst, stiffen and fall to the ground.—Jen Waters, The Washington Times, 4 July 2006 Most often, though, they [seizures] fall in a well-documented spectrum of mental and somatic anomalies, from the transient episodes of decreased awareness known as absence (formerly called “petit mal”) to the tonic-clonic (or “grand mal”) attack characterized by loss of consciousness, collapse and spasmodic stiffening and jerking.—Jerry Adler and Eliza Gray, Newsweek, 20 Apr. 2009
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