Abstracts

Rationale: Cryptogenic West syndrome (C-WS) has normal development before the onset, and no structural abnormalities are observed on conventional MRI. However, seizure and developmental outcome is very diverse. Diffusion tensor imaging (DTI) is an MRI technique that can provide information about white matter fiber orientation and integrity. We prospectively performed DTI to assess white matter abnormality in patients with C-WS. The results were compared with focal cortical hypometabolism on FDG-PET to clarify if the white matter abnormality on DTI may reflect underlying focal lesions.Methods: We studied 14 consecutive patients with C-WS. DTI using 3T MRI (3.0T Trio, Siemens) and FDG-PET were acquired at 24 months of age. Images of fractional anisotropy (FA) in patients were compared with those of 13 controls with mean age 24 months. 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. Regions with significant differences were identified with threshold: p<0.05. FDG-PET images at 24 months of age were analyzed with visual inspection to identify cortical hypometabolism. We compared FA images in patients with PET hypometabolism or patients without hypometabolism with those of controls by TBSS analysis. We also compared FA images in subgroups of patients with right side hypometabolism or left side hypometabolism with those of controls.Results: FDG-PET revealed cortical hypometabolism in 7 of 14 patients. Five of 7 patients with hypometabolism had persistent or recurrent seizures after initial treatments, while 5 of 7 patients without hypometabolism were free of seizures after initial treatments. Four patients had hypometabolism in the left hemisphere, 2 patients had hypometabolism in the right hemisphere, and 1 patient had bilateral hypometabolism. TBSS analysis showed decreased FA in widespread white matters in 7 patients with PET hypometabolism, but not in 7 patients without hypometabolism. Both patients with right side hypometabolism and patients with left side hypometabolism had decrease of FA in symmetrical bilateral white matters.Conclusions: Patients with PET hypometabolism had white matter abnormality on DTI. Distribution of the white matter abnormality was diffuse and not consistent with localization of PET hypometabolism. DTI abnormality in patients with C-WS may not reflect micro-structural abnormality of focal cortical dysplasia, but rather delayed maturation of diffuse white matters.