Atonic elements combined or uncombined with epileptic spasms in infantile spasms

•Atonia combined or uncombined with spasms was an ignored phenomenon in infantile spasms.•Atonic elements combined or uncombined with spasms were artificially divided into three subtypes.•Atonic elements in infantile spasms might be a variant of epileptic spasms or a new seizure type.

ObjectiveTo study the atonic elements combined or uncombined with epileptic spasms in infantile spasms.MethodsThe demographic data, clinical characteristics, electroencephalogram (EEG), and polyelectromyography (PEMG) features were analyzed in 12 infantile spasm patients with atonic elements.ResultsA total of 29 EEGs were recorded. Hypsarrhythmia or hypsarrhythmia variants were identified during interictal EEG. Insular or clustered epileptic spasms occurred in all. Three subtypes of atonic elements combined or uncombined with epileptic spasms (spasm-atonic, pure atonic, and atonic-spasm seizures) were observed electroclinically, which could present insularly or in cluster or altered with epileptic spasms in the same cluster. The ictal EEG showed generalized high-amplitude slow waves presenting alone or combined with other patterns. The corresponding PEMG showed an obvious electrical silence alone or preceding or following a crescendo-decrescendo pattern generated from myoelectric burst.ConclusionsAtonic elements combined or uncombined with epileptic spasms was a newly noticed phenomenon in infantile spasms, which was artificially divided into three subtypes here. It might be a variant of epileptic spasms or a unique seizure type.SignificanceAtonic elements combined or uncombined with epileptic spasms was a previously ignored phenomenon in infantile spasms, which should be seriously considered in clinical practice.