Early-onset spontaneously relieved spasms of infancy in sleep: electroclinical characteristics and differential diagnoses

Objectives: Infantile spasm-like paroxysms are often difficult to classify as epileptic or non-epileptic. We aimed to study spontaneously relieved (non-epileptic) spasms of infancy in sleep. Elucidation of the electroclinical characteristics and differential diagnoses of such spasms could facilitate accurate diagnosis in the future. Methods: We retrospectively analyzed the clinical data, video-EEG recordings, and other laboratory test results of patients with spontaneously relieved spasms of infancy during sleep. All the enrolled patients were followed up at least 5 months. Results: Seven infants were included in this study. The median age at spasm onset was 0.5 months (range: 0.1-2 months). The episodes were characterized by clusters of non-epileptic spasms of the head, trunk, or extremities lasting approximately 0.5 - 2 seconds, and were validated by ictal electromyography (EMG)/video EEG. All episodes occurred several times daily in clusters, particularly during sleep; two patients also experienced episodes while awake. Additionally, non-epileptic jerks were recorded in 3 patients. All non-epileptic spasms were completely resolved 2 weeks to 3 months after onset. Moreover, neuropsychomotor development in all patients was normal at the last follow-up (5 to 12 months). Conclusions: Spontaneously relieved spasms of infancy in sleep is a self-limiting movement disorder characterized by onset between 0.1 and 2 months of age, and by clusters of spasms occurring in sleep. Correct differential diagnosis relies on familiar clinical and electrophysiological features.