Microstructural and volumetric abnormalities of the putamen in juvenile myoclonic epilepsy

Patients with juvenile myoclonic epilepsy (JME) show evidence of microstructural white matter (WM) damage of thalamocortical fiber tracts and changes of blood oxygen level dependent (BOLD) signal in a striatothalamocortical network. The objective of the present study was to investigate microstructural and volumetric alterations of the putamen in patients with JME using diffusion tensor imaging (DTI) and conventional magnetic resonance imaging (MRI).

We performed DTI and MRI for 10 patients with JME and 59 age-matched neurologically healthy volunteers. Evaluation of microstructural damage was investigated using calculation of mean fractional anisotropy (FA) values in a priori regions of interest (ROIs) for the putamen, frontal lobe, and a thalamocortical region, after application of an improved eddy current correction method and a new statistical parametric mapping (SPM)-compatible toolbox incorporating intensive multicontrast FA image registration. Stereologic analysis on MRI was performed to estimate macroscopic volume of the putamen in both cerebral hemispheres for all subjects.

Relative to controls, patients had significantly reduced FA in the frontal lobe (p = 0.01) and thalamocortical fiber WM (p < 0.001). In contrast, putamen FA was bilaterally increased (p = 0.01) and correlated with decreasing putamen volume (r(2) = -0.63, p = 0.004) in patients only. Putamen FA correlated negatively with onset of JME (total: r(2) = -0.50, p = 0.01), duration of JME (r(2) = 0.52, p = 0.01), and thalamocortical fiber FA (r(2) = -0.47, p = 0.01).

This is the first evidence of combined microstructural and macrostructural putamen abnormalities in patients with JME, with early age of onset and a longer duration of epilepsy being significant predictors for greater architectural alterations. These findings are consistent with studies indicating neurophysiologic abnormalities of frontostriatal networks in patients with JME, and may contribute to explain the frequent presentation of executive dysfunction in these patients. Confirmation and further exploration of the increase in putamen FA in patients with JME is required in larger samples.