Focal motor seizure focal motor seizure with negative myoclonus true true https://www.ncbi.nlm.nih.gov/pubmed/8848969 A sudden interruption in normal tonic muscle activity lasting 500 milliseconds or less, without evidence of preceding myoclonus. This is seen in the epilepsy syndrome atypical childhood epilepsy with centrotemporal spikes, where an upper limb or the head is affected by localized brief interruption in normal muscle tone. The interruption in muscle tone is briefer than seen in a focal atonic seizure. The patient may correct for the loss of tone with overshoot past the primary position.