What characterizes a tonic-clonic seizure?

A tonic-clonic seizure is characterized by a sudden loss of consciousness followed by muscle contractions and jerking movements that typically involve multiple muscle groups bilaterally. The seizure consists of two phases: the tonic phase, where the person’s muscles stiffen and they lose consciousness, followed by the clonic phase, which is marked by rhythmic jerking of the limbs. This combination of symptoms distinguishes tonic-clonic seizures from other types of seizures, which may not involve loss of consciousness or generalized muscle contractions.

The other options describe different phenomena that are not indicative of tonic-clonic seizures; for instance, localized symptoms would suggest a focal seizure rather than a generalized seizure like tonic-clonic. Changes in behavior that mimic seizures can refer to non-epileptic seizures or other medical conditions affecting behavior without the characteristics of true epilepsy, while inflammation of the gray matter of the spinal cord pertains to conditions such as myelitis, which is unrelated to the seizure activity.