ObjectiveEpileptic spasms are a type of seizure defined as a sudden flexion or extension predominantly of axial and/or truncal limb muscles that occur with a noticeable periodicity. Routine electroencephalogram supports the diagnosis of epileptic spasms, which can occur due to different causes. The present study aimed to evaluate a possible association between the electro-clinical pattern and the underlying etiology of epileptic spasms in infants.Materials and methodsWe retrospectively reviewed the clinical and video-EEG data on 104 patients (aged from 1 to 22  months), admitted to our tertiary hospital in Catania and the tertiary hospital in Buenos Aires, from January 2013 to December 2020, with a confirmed diagnosis of epileptic spasms. We divided the patient sample into structural, genetic, infectious, metabolic, immune, and unknown, based on etiology. Fleiss’ kappa (К) was used to assess agreement among raters in the electroencephalographic interpretation of hypsarrhythmia. A multivariate and bivariate analysis was conducted to understand the role of the different video-EEG variables on the etiology of epileptic spasms. Furthermore, decision trees were constructed for the classification of variables.ResultsThe results showed a statistically significant correlation between epileptic spasms semiology and etiology: flexor spasms were associated with spasms due to genetic cause (87.5%; OR < 1); whereas mixed spasms were associated with spasms from a structural cause (40%; OR < 1). The results showed a relationship between ictal and interictal EEG and epileptic spasms etiology: 73% of patients with slow waves and sharp waves or slow waves on the ictal EEG, and asymmetric hypsarrhythmia or hemi hypsarrhythmia on the interictal EEG, had spasms with structural etiology, whereas 69% of patients with genetic etiology presented typical interictal hypsarrhythmia with high-amplitude polymorphic delta with multifocal spike or modified hypsarrhythmia on interictal EEG and slow waves on the ictal EEG.ConclusionThis study confirms that video-EEG is a key element for the diagnosis of epileptic spasms, also playing an important role in the clinical practice to determine the etiology.