Myoclonus in childhood-onset neurogenetic disorders: The importance of early identification and treatment

• Early identification and treatment of myoclonus in childhood-onset neurogenetic disorders can lead to significant improvement.
• Searching for myoclonus in childhood-onset neurogenetic disorders is important, even with an established molecular diagnosis.
• We provide a list of childhood-onset neurogenetic disorders with myoclonus as important associated feature (Supplement).

BackgroundIn clinical practice, myoclonus in childhood-onset neurogenetic disorders frequently remains unrecognized, because it is often overshadowed by other neurological features. Since treatment can lead to significant functional improvement, accurate phenotyping is essential. To demonstrate the importance of early identification and treatment, we report on four patients with various childhood-onset neurogenetic disorders suffering from myoclonus.MethodsWe evaluated four patients with established childhood-onset neurogenetic disorders and involuntary jerky movements, who visited our young-onset movement disorder outpatient clinic.ResultsWe present the clinical data of four patients (aged 8–21 years) with childhood-onset neurogenetic disorders, including ataxia-telangiectasia, Coffin-Lowry syndrome and epileptic encephalopathy due to SCN1A mutations. All four suffered from jerky movements that hampered normal daily activities and that had gone unrecognized for several years. The presence of multifocal myoclonus was confirmed by polymyography. In all patients, treatment resulted in marked improvement of both myoclonus and overall functioning.ConclusionThese cases highlight the relevance of actively searching for myoclonus in childhood-onset neurogenetic disorders, even when a molecular diagnosis has already been established. To further improve the awareness and recognition of myoclonus in children, we provide a list of childhood-onset neurogenetic disorders with myoclonus as important associated feature.