Related Experiment Videos
Paroxysmal movement disorders in severe myoclonic epilepsy in infancy
Yoko Ohtsuka1, Iori Ohmori, Tatsuya Ogino
1Department of Child Neurology, Okayama University Graduate School of Medicine and Dentistry, 2-5-1 Shikatacho, Okayama, Japan. ohtsuka@md.okayama-u.ac.jp
Insights
Severe myoclonic epilepsy in infancy patients may experience movement disorders due to anti-epileptic drug therapy, particularly phenytoin. Genetic factors and sodium channel dysfunction may predispose patients to these adverse effects.
Area of Science:
- Epilepsy genetics
- Clinical neuropharmacology
- Pediatric neurology
Background:
- Severe myoclonic epilepsy in infancy (SME) and borderline SME (BSME) are epilepsy syndromes.
- Paroxysmal movement disorders like choreoathetosis and dystonia can occur in epilepsy patients.
- The role of anti-epileptic drugs (AEDs) in precipitating these movements is not fully understood.
Observation:
- Patients with typical SME and BSME exhibited paroxysmal movement disorders during treatment.
- These movements resolved upon reduction or discontinuation of phenytoin (PHT).
- Some patients experienced similar movements even without PHT treatment, suggesting complex interactions.
Findings:
- One TSME and two BSME patients had SCN1A gene mutations, indicating a genetic predisposition.
- Phenytoin therapy was strongly associated with the onset of paroxysmal movement disorders.
- Sodium channel dysfunction may contribute to the predisposition for movement disorders in SME and BSME.
Implications:
- Clinicians should monitor for movement disorders in SME/BSME patients, especially those on PHT.
- Understanding the interplay between genetics, AEDs, and movement disorders is crucial for optimizing epilepsy management.
- Further research into sodium channel dysfunction and its role in AED-induced movement disorders is warranted.
Abstract:
We report on the electroclinical findings and the results of a molecular genetic study of a patient with typical severe myoclonic epilepsy in infancy (TSME) and three with borderline SME (BSME) who showed paroxysmal movement disorders, such as choreoathetosis, dystonia and ballismus, during their clinical course. BSME was defined as a clinical entity that shares common characteristics with TSME but lacks myoclonic seizures associated with ictal EEG changes. When the paroxysmal movement disorders were first observed, all the patients in this study were being treated with polytherapy including phenytoin (PHT), and these abnormal movements disappeared when PHT was discontinued or reduced. However, on other occasions, two of our cases also showed the same abnormal movements even when not being treated with PHT. One patient with TSME and two of the three patients with BSME had SCN1A gene mutations that lead to truncation of the associated protein. We conclude that paroxysmal movement disorders seen in SME patients were closely related to their AED therapy, especially the use of PHT. It is thought that patients with both TSME and BSME have some predisposition toward paroxysmal movement disorders, and that this predisposition is partly related to sodium channel dysfunction, although some other factors might influence the occurrence of this phenomenon.