Focal seizures occur with behavioural arrest, impaired awareness, automatisms, head/eye version, and clonic movements (often alternating from one side to the other, and progressing to a hemiclonic or focal to bilateral tonic-clonic seizure). Seizures are brief (<3 minutes) but frequent e.g. 5-10 per day over 1-3 days at onset. One third of patients present with a single isolated seizure 10-15 days before frequent seizures commence. Longer seizures (3-6 minutes in duration) can occur at onset and in familial cases. Seizures abate but may recur after 1-3 months in a third of patients.
CAUTION Prolonged focal or hemiclonic seizures (>10 minutes) are not seen in this syndrome consider Dravet syndrome.