Myoclonic seizure

What it is

A myoclonic seizure is brief, often repetitive, jerking movements of the limbs, neck or trunk. Consciousness and memory are not impaired.

It sits inside the wider division of seizures. Partial seizures are simple partial with no LOC, complex partial with LOC, and partial seizure with secondary generalization. Generalized seizures are either nonconvulsive, which is the absence seizure, or convulsive: tonic, myoclonic, clonic or tonic clonic.

The same movement is also seen physiologically, in hiccoughs, which are myoclonus of the diaphragm, and on passing through stage II sleep, which is sleep myoclonus.

How it presents

A myoclonic seizure may cause a child to spill or drop what s/he is holding, or to fall from his/her chair.

The seizure set beside it is the atonic one, and the two are told apart by consciousness. In sudden loss of muscle tone the child abruptly loses consciousness without warning, collapses and falls to the floor, with no convulsion; after a few seconds the child regains consciousness and can stand and walk again, usually with no postictal confusion. A very brief atonic seizure may cause a quick head drop or nodding movement, while a longer one will cause the patient to collapse.