What happens in the tonic and in the clonic phase of a convulsive seizure? · Grey Matter

In the tonic phase, about 10 to 20 seconds long, the discharge drives the motor system continuously, so muscles contract together and stay contracted; the EEG shows fast activity building into high-amplitude polyspikes.

What happens in the tonic and in the clonic phase of a convulsive seizure?

In the tonic phase, about 10 to 20 seconds long, the discharge drives the motor system continuously, so muscles contract together and stay contracted; the EEG shows fast activity building into high-amplitude polyspikes. In the clonic phase the discharge is broken by pauses, each a slow wave on the EEG during which inhibition gains ground, and every burst between pauses is a jerk. The pauses lengthen until the seizure ends, usually within a minute or two, and the exhausted brain enters the postictal state of sleep and confusion.