Cortical (reflex) myoclonus vs. focal task-specific myoclonic dystonia: A case report

Many syndromes have been identified, characterised by movement disorders (MD): idiopathic torsion dystonia, task-specific focal dystonia, myoclonic dystonia (all with frequently positive family history, subcortical origin and no jerklocked cortical correlates), cortical reflex myoclonus (CRM) and reticular reflex myoclonus (RRM). We present a young boy who shares many signs with each of these syndromes. This patient, aged 8 years 6 months, suffered from moderate birth asphyxia, 2"d day convulsions, brain diffused oedema and spiky EEC, treated with PB for 12 months. He grew normally and was left-handed. When 7 years old, after a febrile generalised convulsion, he began to show task-specific MD, characterised by proximal dystonia, distal myoclonus (simultaneous cocontraction of antagonist muscles, lasting 40-150 ms) when writing. After a short period, spontaneous and reflex cortical myoclonus (a spike preceded the shock-like jerk on polygraphic study) appeared at rest and during activity. The boy was obliged to use his right hand, that almost immediately showed the same movement problem: dystonia plus myoclonus. MRI study showed trigonal white malter hyperintensity. He was treated with VPA, with remission of right hand dis-turbances and diminution of reflex responses. At that time, SEP study was normal and C-reflex was absent. We think that this boy has symptomatic cortical hyperexcitability with cortical spontaneous and reflex shock-like or longer myoclonus, linked to a task-specific dystonia and a RRM. which responded to antiepileptic therapy. It is difficult to classify myoclonic dystonia, which seems to be symptomatic too, but is of subcortical origin. In light of these data, we feel it is difficult to conclude if the patient suffers from partial reflex epilepsy or a complex movement disorder.