Nerve fiber impairment of anterior thalamocortical circuitry in juvenile myoclonic epilepsy

Abstract

<b>Background:</b> Juvenile myoclonic epilepsy (JME) is a syndrome of idiopathic generalized epilepsy (IGE) without structural brain abnormalities detectable by MRI or CT. <b>Objective:</b> 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. <b>Methods:</b> 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”). <b>Results:</b> 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 (<i>p</i> &lt; 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, <i>p</i> = 0.05). No significant correlations were found in the JME sample between FA reduction and the duration of antiepileptic medication. <b>Conclusions:</b> 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. <b>CPE</b> = cryptogenic partial epilepsy; <b>DTI</b> = diffusion tensor imaging; <b>EPI</b> = echoplanar imaging; <b>FA</b> = fractional anisotropy; <b>GMC</b> = gray matter concentration; <b>GTCS</b> = generalized tonic-clonic seizures; <b>IGE</b> = idiopathic generalized epilepsy; <b>JME</b> = juvenile myoclonic epilepsy; <b>MNI</b> = Montreal Neurological Institute; <b>ROI</b> = region of interest; <b>VBM</b> = voxel based morphometry; <b>WM</b> = white matter.