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Hippocampal sclerosis in severe myoclonic epilepsy in infancy: a retrospective MRI study
Zsuzsanna Siegler1, Peter Barsi, Magdolna Neuwirth
1Epilepsy Center, Bethesda Children's Hospital, Budapest, Hungary.
Purpose:
Severe myoclonic epilepsy in infancy (SMEI; Dravet's syndrome) is a malignant epilepsy syndrome characterized by early prolonged febrile convulsions (PFCs) with secondary psychomotor delay and a variety of therapy-resistant seizures. Although the initial symptoms are repeated PFCs, the MRI performed at the onset of disease shows no hippocampal structural abnormalities. We aimed to assess clinical and serial MRI data of patients with SMEI with a special attention to the temporomedial structures. To our knowledge, this is the first systematic MRI study in this disease.
Methods:
Clinical and MRI data of all SMEI patients treated in our hospitals between 1996 and 2004 were reviewed.
Results:
Twenty-eight MRIs from 14 children (one to four images/patient) were included. Age at disease onset was between 3 and 9 months; age at initial MRI was 5 months to 13 years. Ten of 14 patients showed hippocampal sclerosis (HS) during the course of the disease (nine unilateral, one bilateral). Six of these 10 had a normal initial MRI. Age at the first verified HS was between 14 months and 13 years. Neither complex partial seizures nor anterior temporal irritative zone was recorded in these children.
Conclusions:
After initially normal structures, in most patients with SMEI, HS develops several months or years after the first PFC. These data support the hypothesis that PFC might be responsible for HS, but other factors and individual sensitivity should play a role in this process.
Insights
Hippocampal sclerosis (HS) develops in most children with Severe Myoclonic Epilepsy in Infancy (SMEI) months or years after initial prolonged febrile convulsions (PFCs). Early MRIs may appear normal, highlighting the progressive nature of HS in SMEI.
Area of Science:
- Neurology
- Pediatric Neurology
- Epileptology
Background:
- Severe Myoclonic Epilepsy in Infancy (SMEI), also known as Dravet's syndrome, is a severe epilepsy characterized by prolonged febrile convulsions (PFCs) and developmental delay.
- Initial MRIs in SMEI patients typically show no hippocampal abnormalities, despite PFCs being the primary symptom.
Observation:
- This study systematically reviewed clinical and serial MRI data from 14 children with SMEI.
- Twenty-eight MRIs were analyzed, with a focus on temporomedial structures.
Findings:
- Hippocampal sclerosis (HS) developed in 10 out of 14 patients during the disease course, with nine showing unilateral and one bilateral HS.
- Six of these 10 patients had normal initial MRIs, with HS appearing between 14 months and 13 years of age.
- No complex partial seizures or anterior temporal irritative zones were noted in affected children.
Implications:
- The findings suggest that HS in SMEI may develop progressively, potentially years after the initial PFCs.
- Prolonged febrile convulsions (PFCs) are hypothesized to contribute to HS development, though individual sensitivity and other factors likely play a role.
- This research underscores the importance of serial MRI monitoring in diagnosing and understanding the pathophysiology of SMEI.
