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Teaching NeuroImage: Hemiconvulsion-hemiplegia-epilepsy syndrome: Sequential MRI follow-up

Division of Pediatric Neurology, Department of Pediatrics, All India Institute of Medical Sciences, New Delhi, 110029 India.
Neurology (Impact Factor: 8.3). 10/2008; 71(11):e28. DOI: 10.1212/01.wnl.0000325475.04616.e3
Source: PubMed
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    ABSTRACT: Hemi convulsion-hemiplegia syndrome (HHS) is a rare severe epilepsy of infancy consisting of unilateral convulsive status epilepticus immediately followed by transient or lasting ipsilateral hemiplegia. HHS may occur either in patients with previous brain pathology or without any identified cause, so-called 'idiopathic HHS'. We retrospectively analysed clinical and MRI longitudinal findings of a series of 10 patients (six females, four males) presenting with HHS. Age at the study inclusion ranged from 2 years 6 months to 15 years (mean of 5y 10mo, median 4y 2mo). After defining magnetic resonance imaging (MRI) features as 'typical', i.e. strictly unilateral involvement, and 'atypical', i.e. bilateral, we compared clinical data from both groups. Cognitive level was assessed using Brunet-L├ęzine or Wechsler scales. HHS occurred at a mean age of 20.5 months (range 8-48mo). In all cases, status epilepticus lasted for more than 1 hour and was characterised by unilateral clonic seizures followed by ipsilateral hemiplegia (persistent in five patients). Two patients in this series died: the first from multi-organ failure 2 weeks after the status epilepticus and the other from a second episode of ipsilateral intractable febrile status epilepticus 3 years after the first episode. Early MRI (days 1-7 from status epilepticus) showed hemispheric cytotoxic oedema in all, extending to the contralateral side for one. T2 hyperintensity in the basal ganglia was disclosed in 70% of patients and in the hippocampus in 60%. After 1 month (in intermediate and chronic phases), all surviving patients but one showed hemispheric cortical atrophy corresponding to the regions involved during the early stage. Comparing clinical features of patients presenting with 'typical' features, to those with 'atypical' findings, the second group presented psychomotor delay before status epilepticus. This series underlines the major value of early MRI for the prompt diagnosis of HHS, and shows that involvement of subcortical structures has been underestimated. Hippocampal involvement is not constant.
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    ABSTRACT: Hemiconvulsion-hemiplegia-epilepsy (HHE) syndrome is an uncommon outcome of prolonged focal status epilepticus in childhood. The prolonged focal motor seizure usually occurs during the course of a febrile illness and is followed by hemiplegia ipsilateral to the side of convulsions. This is accompanied by radiologic evidence of acute cytotoxic edema in the affected hemisphere followed by chronic atrophy. Intractable epilepsy may develop at a time remote from the initial presentation. The clinical features of HHE syndrome were first described more than 5 decades ago but its pathophysiology remains poorly understood and the long-term cognitive outcomes are unclear. Early recognition of the syndrome may help provide patients and families with an accurate prognosis regarding the subsequent development of epilepsy.
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