Nerve fiber impairment of anterior thalamocortical circuitry in juvenile myoclonic epilepsy

Background: Juvenile myoclonic epilepsy (JME) is a syndrome of idiopathic generalized epilepsy (IGE) without structural brain abnormalities detectable by MRI or CT. Objective: In the present study, we addressed the question of whether diffusion tensor MRI (DTI) can detect disease-specific white matter (WM) abnormalities in patients with JME. Methods: We performed whole head DTI at 3 T in 10 patients with JME, 8 age-matched patients with cryptogenic partial epilepsy (CPE), and 67 age-matched healthy volunteers. Nerve fiber integrity was compared between the groups on the basis of optimized voxel-by-voxel statistics of fractional anisotropy (FA) maps obtained by DTI (analysis of covariance, categorical factor “group,” covariate “age”). Results: FA was reduced in a WM region associated with the anterior thalamus and prefrontal cortex in patients with JME compared to both control subjects and patients with CPE (p < 0.001). The patients with CPE showed normal values in this particular WM region. The FA reductions in the patients with JME correlated with the frequency of generalized tonic-clonic seizures (Spearman R = 0.54, p = 0.05). No significant correlations were found in the JME sample between FA reduction and the duration of antiepileptic medication. Conclusions: The results support the hypothesis that juvenile myoclonic epilepsy is associated with abnormalities of the thalamocortical network that can be detected by diffusion tensor MRI. CPE = cryptogenic partial epilepsy; DTI = diffusion tensor imaging; EPI = echoplanar imaging; FA = fractional anisotropy; GMC = gray matter concentration; GTCS = generalized tonic-clonic seizures; IGE = idiopathic generalized epilepsy; JME = juvenile myoclonic epilepsy; MNI = Montreal Neurological Institute; ROI = region of interest; VBM = voxel based morphometry; WM = white matter.