[SP3-3A-2] Atonic Elements Combined or Uncombined with Epileptic Spasms in Infantile Spasms
Infantile spasms is characterized by an unique type of seizure called epileptic spasms and gross EEG abnormalities of hypsarrhythmia. Here, we report a novel clinical phenomenon that atonic elements combined or uncombined with epileptic spasms in infantile spasms. A total of 29 electroencephalogram (EEG) with polyelectromyography (PEMG) recordings were analyzed in 12 patients with atonic elements. All the patients demonstrated hypsarrhythmia or hypsarrhythmia variants on the interictal EEG. And insular or clustered of epileptic spasms occurred in all. Three subtypes of atonic elements combined or uncombined with epileptic spasms were observed: spasm-atonic seizures, pure atonic seizures and atonic-spasm seizures, which could present insularly or in cluster, or altered with epileptic spasms in the same cluster. Similarly to epileptic spasms, its ictal EEG showed generalized high-amplitude slow waves presenting alone or combined with other patterns, such as episodes of fast activity or voltage attenuation. And the corresponding PEMG showed an obvious electrical silence alone, or preceding or following a crescendo-decrescendo pattern generated from myoelectric burst. Most patients were refractory to various antiepileptic drugs or adrenocorticotropic hormone. At the last follow-up, all patients available had severe psychomotor development delay. In conclusion, atonic elements combined or uncombined with epileptic spasms was a new electro-clinical phenomenon noticed in infantile spasms, which was ignored previously and should be taken seriously in clinical practice. It might be a variant of the epileptic spasms or an unique seizure type, but further studies are needed for clarifying the detailed neurophysiologic mechanism in the future.