Structural Brain Abnormalities in Epilepsy with Myoclonic Atonic Seizures

Objectives: Epilepsy with myoclonic atonic seizure (EMAS) is a rare generalized epilepsy syndrome with early seizure onset children with normal to subnormal development. Routine brain imaging shows no abnormalities. The course is highly variable, ranging from seizure freedom with preserved cognitive abilities to refractory epilepsy with intellectual disability (ID). Fine motor and executive deficits are frequently observed on follow-up. This study aims at evaluating the brain morphology of EMAS patients compared with healthy participants, several years after epilepsy onset, and to correlate these findings to epilepsy and cognitive outcome.

Content: Methods: Fourteen EMAS patients (four females, 5–14 years of age) and 14 matched healthy controls were included in the study. Clinical evaluations were used to classify the patients into three outcome groups. Group 1: no seizure, normal cognition ± minor executive and/or learning difficulties; group 2: no seizure, normal intellectual quotient (IQ), marked executive, and learning difficulties; group 3: active epilepsy and mild-to-moderate ID. Individual anatomical data (T1-weighted sequence) were processed and used for group-comparison using the FreeSurfer 5.1.0 software to extract cortical volume (CV), cortical thickness (CT), local gyrification index (LGI), and subcortical volumes (basal ganglia and cerebellum).

Results: Morphometric comparison between EMAS patients and healthy controls revealed (1) reduced CV in frontal, temporal, and parietal lobes (p ≤ 0.001, 0.009, and 0.024 respectively); (2) reduced CT and LGI in frontal lobes (p = 0.036 and 0.032, respectively); and (3) analyses of subcortical structures only showed cerebellar volume reduction (p = 0.011). The worse outcome was correlated to lower LGI in parietal, temporal, occipital lobes, and cingulate gyrus. The number of antiepileptic drugs was negatively correlated to thalamic but not cerebellar volumes.

Conclusion: Structural brain changes were detectable in our small sample of children with EMAS and were mainly located in the frontal lobes and cerebellum. These findings are similar to those found in patients with genetic/idiopathic generalized epilepsies who share similar seizures and cognitive characteristics. Outcome was best correlated with LGI that seems to be a more sensitive indicator of aberrant prenatal brain development than CV and CT. Whether these changes reflect genetically determined abnormal neuronal networks or a consequence of epilepsy remains to be solved with prospective longitudinal studies.

Publication History

Article published online:
16 March 2022