Abstracts

Rationale: In patients with Dravet syndrome MRI studies usually do not demonstrate brain lesions except mild or moderate cerebral, cerebellar or hippocampal atrophy. We performed diffusion tensor imaging (DTI) to reveal white matter abnormality in patients with Dravet syndrome. Methods: We studied 7 patients with Dravet syndrome. Age at the scan was from 6 to 13 years (mean 9 years). Status epilepticus was observed 1 to 10 times in each patient. One patient had scans twice at 6 and 11 years of age. Conventional MRI revealed enlargement of lateral ventricles or subarachnoid space in 2 patients, and right hippocampal mild atrophy and high intensity on T2-weighted image 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). TBSS projects all subjects' FA data onto a mean FA tract skeleton, before applying voxelwise cross-subject statistics. FA images of patients were compared with those of 36 controls from 5 to 14 years of age (mean 9 years). Age was used as nuisance covariate of no interest. Regions with significant differences were identified with threshold: p<0.05. TBSS analysis was also performed on axial, radial, and mean diffusivity. We calculated mean value of FA in the skeleton with significant difference on TBSS in each subject, and compared the FA values in patients with seizure frequency or number of status epilepticus. Results: TBSS revealed significantly decreased FA in widespread white matters of patients. Axial diffusivity increased dominantly in frontal white matters, and radial diffusivity increased in widespread whole white matters. Patients with frequent seizures and status epilepticus had more reduced FA compared with those of patients with less frequent seizures. Conclusions: DTI revealed widespread white matter abnormality in patients with Dravet syndrome. Frequent seizures may cause the wide spread white matter damage.