The epileptology of alternating hemiplegia of childhood.

Objective: To report our experience and investigate 5 original hypotheses: (1) multiple types of epileptic seizures occur in alternating hemiplegia of childhood (AHC), and these can be the initial presentation; (2) epileptiform abnormalities often appear well after clinical seizures; (3) nonepileptic reduced awareness spells (RAS) occur frequently; (4) epilepsy is commonly drug resistant but may respond to vagal nerve stimulation (VNS); and (5) status epilepticus (SE) is common and is usually refractory and recurrent.

Methods: We analyzed a cohort of 51 consecutive patients with AHC.

Results: Thirty-two of 51 patients had epilepsy: 18 focal seizures, frontal more frequently than temporal, and then posterior. Eleven had primary generalized seizures (tonic-clonic, myoclonic, and/or absence). Epileptic seizures preceded other AHC paroxysmal events in 8 (lag 5.63 ± 6.55 months; = 0.0365). In 7 of 32, initial EEGs were normal, with the first epileptiform EEG lagging behind by 3.53 ± 4.65 years ( = 0.0484). RAS occurred equally in patients with epilepsy (16 of 32) and patients without epilepsy (10 of 19, = 1.0). Twenty-eight patients had video-EEG; captured RAS showed no concomitant EEG changes. Nineteen patients (59%) were drug resistant. VNS resulted in >50% reduction in seizures in 5 of 6 ( < 0.04). Twelve patients (38%) had SE (9 of 12 multiple episodes), refractory/superrefractory in all ( < 0.001), and 4 of 12 had regression after SE.

Conclusions: Epilepsy in AHC can be focal or generalized. Epileptic seizures may be the first paroxysmal symptom. EEG may become epileptiform only on follow-up. Epilepsy, although frequently drug resistant, can respond to VNS. RAS are frequent and nonepileptic. SE often recurs and is usually refractory/superrefractory. Our observations are consistent with current data on AHC-ATP1A3 pathophysiology.