Abstracts

Rationale: Majority of patients with Dravet syndrome exhibit no gross abnormalities on brain MRI, although cerebral atrophy, increased white matter signal, and hippocampal atrophy were occasionally reported. Main question is whether these brain damages are caused by intractable seizures. We performed diffusion tensor imaging (DTI) and hippocampal volume (HV) measurements, and compared the results with seizure frequency to reveal the correlation of brain damages and seizures.Methods: We studied 8 patients with Dravet syndrome. Age at the scan was from 6 to 14 years (mean 9 years). Status epilepticus was observed 0 to 10 times in each patient (median 3 times). Number of seizures within 1 year before the scans except for myoclonic jerks and absences was from 3 to 200. Conventional MRI revealed right hippocampal atrophy in 1 patient. DTI was acquired using 3T MRI (3.0T Trio, Siemens) and fractional anisotropy (FA) images were constructed. Statistical analysis of FA images was carried out using tract-based spatial statistics (TBSS) implemented in FSL (The Oxford FMRIB Software Library). FA images of patients were compared with those of 36 controls by TBSS. We calculated a mean FA value in the skeleton with significant difference on TBSS in each subject, and compared the FA values in patients with seizure frequency within 1 year before the scan. HV measurements were carried out on T1-weighted 3D MPRAGE sequence. HVs were compared with those of controls and seizure frequency.Results: TBSS revealed significantly decreased FA in widespread white matters of patients. Patients with frequent seizures and status epilepticus had more reduced mean FA values compared with those of patients with less seizures. Left HV in patients were smaller than those of controls. HV were not correlated with seizure frequency.Conclusions: Patients with Dravet syndrome have widespread white matter abnormality and small left hippocampus. Frequent seizures may cause the wide spread white matter damage. On the other hand, HV reduction is related to other factors than frequent seizures and status epilepticus.