Abstract:

Objective Atonic seizures occur without warning, and children with this condition may repeatedly fall, seriously affecting their safety and quality of life. Accurate diagnosis and management of atonic seizures are rather difficult, and the electroencephalography (EEG) and electromyography (EMG) features during the seizure period are the gold standard for differential diagnosis. This study summarizes the clinical, EEG, and EMG characteristics, treatment, and prognosis of children with epilepsy who have atonic seizures, with the aim of providing a reference for clinicians to correctly diagnose and treat this disease. Methods A retrospective analysis was conducted on the clinical data of children with atonic seizures admitted to the neurology department from August 2015 to December 2023. The clinical characteristics, etiology, treatment and follow-up of the children were analyzed and summarized. Results A total of 47 children had atonic seizures, including 32 boys and 15 girls. The median age of onset was 2.17 (1.17-2.92) years. Among them, 7 children had structural causes, 10 had hereditary causes, 1 had hereditary structural cause, and the causes were unknown in 29 children. The types of atonic seizures included generalized atonic seizures (33 cases), myoclonic-atonic seizures (5 cases), spasm-atonic seizures (2 cases), atypical absence seizures with atonic seizures (2 cases), both atonic seizures and myoclonic-atonic seizures (4 cases), and focal atonic seizures (1 case). The patients often have other types of seizures, with myoclonic seizures being the predominant type (15/47, 31.9%), followed by atypical absence seizures (6/47), and spasms (5/47), etc. Among the 47 children, the type of epileptic syndromes was clearly identified in 13 cases. Among them, 6 cases had epilepsy with myoclonic atonic seizures (EMAS), 5 had infantile epileptic spasms syndrome (IESS), 1 had Lennox-Gastaut syndrome (LGS), and 1 had Dravet syndrome (DS). Among the 47 patients, except for 5 patients with normal development, the remaining 42 all have some degree of intellectual disability. During atonic seizures, EEG manifestations included spike-slow waves in 20 cases, slow waves in 13 cases, multispike-slow waves in 8 cases, low-amplitude fast rhythms in 2 cases, slow waves composite fast waves in 2 cases, and slow waves followed by low-amplitude fast rhythms in 1 case. No EEG changes were observed in 1 case (electromyographic rest only). During seizures, EMG showed electromyographic suppression in 43 cases, while electromyographic suppression was inconspicuous in 4 cases. Among the 47 patients, 27 patients were controlled for at least 6 months without seizures, 14 patients had a 50% reduction in seizure frequency, and 6 patients were ineffective after anti-seizure medication. Conclusions Atonic seizures are more common in males than females and can be combined with multiple seizure forms, which are common in various epileptic syndromes. The etiology is mainly genetic and structural diseases, most of which are accompanied by intellectual disability. The main manifestations of ictal EEG are (multiple) spike slow waves, slow waves, low amplitude fast rhythms, slow wave composite fast waves, and slow waves followed closely by fast rhythms, and unchanged in EEG. Synchronous EMG monitoring is important for detecting atonic seizures.

Key words: atonic seizures, epilepsy, electroencephalography, epileptic syndromes, child