Diffusion tensor imaging of cryptogenic and acquired partial epilepsies

Current optimal MRI identifies a relevant structural abnormality in up to 8 0% of patients with refractory partial seizures, Identification of a struct ural lesion is fundamental to pre-surgical evaluation, We used diffusion te nsor imaging (DTI) and statistical parametric mapping (SPM) to examine obje ctively the diffusion properties, and hence structural organization, of cer ebral tissue in 10 patients with partial seizures and acquired lesions and 30 patients with partial seizures and normal MRI, Fractional anisotropy and mean diffusivity maps were calculated and, using SPR I, individual patient s were compared with a group of 30 control subjects, Diffusion tensor imagi ng and voxel-by-voxel statistical comparisons identified significant increa ses in diffusivity and significant reductions of anisotropy in all patients with acquired nonprogressive cerebral lesions and partial seizures, In all of these patients, the areas of increased diffusivity, and in nine patient s the areas of decreased anisotropy, concurred with abnormalities identifie d on visual inspection of conventional MRI, In addition, there were 10 area s which were normal on conventional imaging which exhibited abnormal anisot ropy or diffusivity, Individual analyses of the 30 patients with partial se izures and normal optimal MRI identified a significant increase in diffusiv ity in eight of the subjects, In six of these, the areas of increased diffu sivity concurred with the localization of epileptiform EEG abnormality, Ana lysis of anisotropy in the MRI-negative patients revealed significant diffe rences in two patients, one of which concurred with electroclinical seizure localization, Group analysis of nine patients with normal conventional MRI and electroclinical seizure onset localizing to the left temporal region r evealed a significant increase in diffusivity and a significant reduction i n anisotropy within the white matter of the left temporal lobe, DTI analyse d using SPM was sensitive in patients with acquired cerebral damage, Signif icant differences in the diffusion indices in individual MRI negative patie nts and the group effect in patients with left temporal lobe epilepsy sugge st that minor structural disorganization exists in occult epileptogenic cer ebral lesions, These techniques are promising, non-invasive imaging methods for identifying the cause of partial seizures, and can contribute to pre-s urgical evaluation.