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Abstract
Objectives: Juvenile myoclonic epilepsy (JME) is characterized by myoclonic jerks of the upper limbs, often triggered by cognitive stressors. Here we aim to reconcile this particular seizure phenotype with the known frontal lobe type neuropsychological profile, photosensitivity, hyperexcitable motor cortex, and recent advanced imaging studies that identified abnormal functional connectivity of the motor cortex and supplementary motor area (SMA).
Methods: We acquired fMRI and diffusion tensor imaging (DTI) in a cohort of 29 patients with JME and 28 healthy control subjects. We used fMRI to determine functional connectivity and DTI-based region parcellation and voxel-wise comparison of probabilistic tractography data to assess the structural connectivity profiles of the mesial frontal lobe.
Results: Patients with JME showed alterations of mesial frontal connectivity with increased structural connectivity between the prefrontal cognitive cortex and motor cortex. We found a positive correlation between DTI and fMRI-based measures of structural and functional connectivity: the greater the structural connectivity between these 2 regions, the greater the observed functional connectivity of corresponding areas. Furthermore, connectivity was reduced between prefrontal and frontopolar regions and increased between the occipital cortex and the SMA.
Conclusion: The observed alterations in microstructural connectivity of the mesial frontal region may represent the anatomic basis for cognitive triggering of motor seizures in JME. Changes in the mesial frontal connectivity profile provide an explanatory framework for several other clinical observations in JME and may be the link between seizure semiology, neurophysiology, neuropsychology, and imaging findings in JME.
GLOSSARY
- DTI=
- diffusion tensor imaging;
- FA=
- fractional anisotropy;
- JME=
- juvenile myoclonic epilepsy;
- MNI=
- Montreal Neurological Institute;
- SMA=
- supplementary motor area
Footnotes
Study funding: Supported by the Wellcome Trust (project grant 079474), the Big Lottery Fund, the Wolfson Trust, and the Epilepsy Society. Infrastructure support was provided by the National Institute for Health Research (NIHR) Specialist Biomedical Research Centre for Mental Health at the South London and Maudsley NHS Foundation Trust and the Institute of Psychiatry, King's College London. Part of this work was undertaken at University College London Hospitals, which received a proportion of funding from the NIHR, Biomedical Research Centres funding scheme.
Supplemental data at www.neurology.org
- Received August 15, 2011.
- Accepted January 17, 2012.
- Copyright © 2012 by AAN Enterprises, Inc.
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