Describe the manifestations of epilepsy in Alternating Hemiplegia of Childhood (AHC) and our experience in managing it.

AHC is characterized by recurrent episodes of hemiplegia, double hemiplegia, dystonia, and, frequently, epilepsy. However, the characteristics of epilepsy in AHC have yet to be described in detail.

We analyzed clinical and electrophysiological data of a cohort of 50 consecutive AHC patients who underwent systematic evaluations as per our clinical pathway.

31/50 had epilepsy (seizure age of onset: 1.89±3.04 years). In seven, seizures preceded other AHC spells. Eighteen (58%) were drug resistant. Seventeen had focal seizures, frontal more frequently than temporal, then parietal, and occipital. Eleven had primary generalized seizures: 11 generalized tonic-clonic (GTC), 3 myoclonic, and 2 absence. Three had GTCs of unknown onset. Therapies includedantiepileptics (31/31), ketogenic diet (6/31), repurposed drugs (11/31) and pulse steroids (2/31), andhad mixed results. Vagal nerve stimulation resulted in >50% reduction in seizure frequency in 5/6. Although the majority had epileptiform EEGs, 7 initially had normal EEGs that later became epileptiform. MRI, normal in the majority, showed in some cerebral atrophy (3/31), cerebellar atrophy (3/31) or abnormal spectroscopy (4/5, all had prior status epilepticus-SE). Eleven (35%) had SE, refractory or super refractory in all. 8/11 had multiple SE episodes. 3/11 had regression after SE.26/50 also had, previously not characterized, spells we termed Reduced Awareness Spells (RAS),consisting of isolated lethargy, drowsiness, staring, and reduced responsiveness without concomitant clinical epileptic manifestations or EEG changes.

Epilepsy in AHC: 1) is focal or generalized, 2) can be the initial manifestation of AHC, 3) manifests high frequency of drug resistance and of often recurrent refractory SE that at times is followed by regression, and 4) RAS, likely non-epileptic in nature, occur frequently.