Myoclonic-atonic Seizure (aka Myoclonic-Astatic)

The myoclonic-atonic seizure is rare and unique to MAE and is one of the most important and distinct features which helps distinguish it from other epilepsy syndromes.

Like myoclonic seizures, myoclonic-atonic seizures (also called atonic or drop attacks) are sudden, single events. Myoclonic-atonic seizures involve abrupt loss of muscle control causing the person to fall to the ground, often resulting in injury. For any family and child, the sudden, violent impact and resultant injuries are seen with myoclonic-atonic seizures make them one of the most frightening and distressing types of seizures to live with.

As the label myoclonic-atonic epilepsy (MAE) suggests, myoclonic-atonic seizures are the core seizure type associated with the disorder. In Doose syndrome, myoclonic-atonic seizures can be serious because they may be difficult to control, occur frequently daily putting the child at persistent risk of injury, and because they are only one manifestation of this mixed seizure disorder.

What happens?

Myoclonic-atonic seizures are sudden involuntary events like myoclonic seizures, however, rather than a sudden increase in muscle tone causing a jerk, atonic seizures involve a sudden loss of muscle tone.

Myoclonic-atonic seizures we see in Doose syndrome involve this atonic seizure (loss of muscle tone) often preceded by a short myoclonic (jerk) component as well. Arms, legs, or torso muscles that support the body by their tone, suddenly go limp; the body gives way with a jolt. The torso may slump, the legs may give way, or the body may fall to the ground. If a myoclonic-atonic seizure occurs while a child is standing, the seizure may cause the child to slam violently to the ground, perhaps hitting his/her face, breaking a tooth, or causing a facial laceration. Some describe this seizure as someone cutting the strings on a marionette puppet.

Like myoclonic seizures, atonic seizures arise from deep structures in the brainstem that control muscle tone. Since the areas that increase tone are close to those that decrease tone, children with seizures involving sudden changes in tone may have either myoclonic or atonic seizures and often both which is what we see typically with Doose syndrome.

As is the case with all generalized seizures, the child is not conscious during the event but the seizure is so brief that he/she usually recovers quickly. Sometimes a child may be mildly agitated or disorientated following an atonic seizure. If an injury has resulted, he/she may be duly distressed.