Hemiconvulsion-hemiplegia-epilepsy syndrome (HHE): Electro-clinical aspects in the acute phase and in the later course in 15 children

Abstract

Objectives Hemiconvulsion-hemiplegia epilepsy (HHE) syndrome is a rare condition occurring in infancy and early childhood, characterized by prolonged clonic convulsions with unilateral predominance followed by ipsilateral hemiplegia during a febrile illness. After a free interval of variable duration, most patients develop epilepsy. HHE may occur either in patients with previous structural brain pathology or without any identified cause, so-called “idiopathic HHE”. We aimed to characterize the electro-clinical aspects observed in the acute phase and in the later course of the disease. Methods Between January 1997 and December 2016, 15 patients (8 girls, 7 boys), presenting with hemiconvulsion-hemiplegia were identified. Mean age was 10 years (range 3–21years) with a mean follow-up of 53 months (range 1–19 years). Electro-clinical features in the acute stage and evolution are described. Two patients died, one girl during the acute phase (on day 7). Results Median age at onset of convulsive status was 27.73 months (range 9–84 months). Status epilepticus lasted 30 minutes up to several days, and was characterized by unilateral clonic seizures in 10 patients and generalized seizures with unilateral predominance in 5 patients. In the acute phase interictal EEG disclosed inter-hemispheric asymmetry (14/15), background slowing (15/15), and spikes and slow sharp-waves (5/15). Seizures were recorded in 3 patients. Periodic lateralized epileptiform discharges were observed in one patient, who died during the acute phase on day 7. All patients presented ipsilateral hemiplegia (10/15 left, 5/15 right). The motor deficit (hemiplegia or hemiparesis) disappeared in 3 patients and persisted in 11, in two of them spastic hemiplegia developed. Eleven patients developed epilepsy after a free interval lasting up to 80 months, in 2 of them pharmaco-resistant. At the end of the observation period, all children with follow-up presented learning difficulties. Conclusion We describe electro-clinical features in the acute phase and in the later course in 15 patients presenting with HHE syndrome.