Abstracts

Rationale: Hemiconvulsion-hemiplegia (HH) syndrome is characterized by the occurrence of prolonged unilateral convulsions during the course of a febrile illness in children less than 4 years of age, followed by ipsilateral, transient or definitive, hemiplegia. Later, focal epilepsy is often observed (Gastaut H., 1960). HH syndrome can be idiopathic or symptomatic; the former being provoked during non-specific febrile episode and the latter emerging in cases with underlying brain pathology (Sakakibara T., 2009). Although the clinical features and natural history of HH syndrome have been well described (Gastaut H., 1960), the differential diagnosis of HH in the acute phase is a challenge requiring exclusion of infective, vascular and metabolic aetiologies. A few neuroradiological longitudinal studies were reported with a peculiar aspect of unilateral brain oedema at the time of the initial status epilepticus (SE), followed by global cerebral hemiatrophy independent of any vascular territory (Sankhyan N., 2008). Methods: We report longitudinal neuroimaging data of 6 patients presenting idiopathic HH syndrome. Results: All 6 patients presented during a febrile illness hemiclonic status epilepticus leading in 4 patients to persistent hemiplegia and to transitory deficit in 2. Median age at last observation was 6.5 years (range: 2.2-15 years). Follow-up ranged from 1 to 13 years. Early MRI (1-10 days from the SE) showed in all a hemispheric cytotoxic oedema. T2 and FLAIR hyperintensities were observed in temporal, parietal and occipital areas in 3 patients, in caudate and thalamus nuclei in 2 and in hippocampus in one. In intermediate stage (11 days- 1 month), the reduction of signal intensity abnormalities and of ADC values were consistent with a reduction of cytotoxic oedema. During late stage (> 6 months), a selective cortical-subcortical atrophy of the affected hemisphere was documented in all, affecting thalamus and caudate nuclei in 2 patients and hippocampus in one. Temporal and occipital gliotic areas were observed in 2 patients. Conclusions: This is the largest series of patients presenting idiopathic HH with longitudinal MRI follow-up including diffusion sequences. Our MRI findings showed a hemispheric cytotoxic reversible oedema involving mostly temporal and posterior cerebral regions and followed by a cortical-subcortical atrophy. We discuss the role of a selective brain vulnerability to an inflammatory-mediated insult in the determinism of HH. From a developmental point of view, an age-depending selective brain vulnerability could act as a modulator on the effects and the extension of inflammatory mechanisms and might explain a large spectrum of immune mediated epilepsies. Caudate and thalamus involvement, not previously reported, suggests a mainly functional and/or metabolic phenomenon.