 This is characterized by ataxia and lethargic behaviour at early stages of development followed within days by the onset of both focal motor seizures as well as episodes of behavioural immobility which correlates with patterns of cortical spike and wave discharges at the EEG A premature-termination mutation R482X was identified in a patient with JME while an additional missense mutation C104F was identified in a German family with generalized epilepsy and praxis – induced seizures.The R482X mutation results in increased current amplitudes and an accelerated fast time constant of inactivation.Whether these modest functional differences may be in charge of JME remains to be established.