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Motor system hyperconnectivity in juvenile myoclonic epilepsy: a cognitive functional magnetic resonance imaging study.

Vollmar C, O'Muircheartaigh J, Barker GJ, Symms MR, Thompson P, Kumari V, Duncan JS, Janz D, Richardson MP, Koepp MJ - Brain (2011)

Bottom Line: With increasing cognitive demand, patients showed increasing coactivation of the primary motor cortex and supplementary motor area.This effect was stronger in patients still suffering from seizures, and was not seen in healthy controls.Furthermore, we found impaired deactivation of the default mode network during cognitive tasks with persistent activation in medial frontal and central regions in patients.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK.

ABSTRACT
Juvenile myoclonic epilepsy is the most frequent idiopathic generalized epilepsy syndrome. It is characterized by predominant myoclonic jerks of upper limbs, often provoked by cognitive activities, and typically responsive to treatment with sodium valproate. Neurophysiological, neuropsychological and imaging studies in juvenile myoclonic epilepsy have consistently pointed towards subtle abnormalities in the medial frontal lobes. Using functional magnetic resonance imaging with an executive frontal lobe paradigm, we investigated cortical activation patterns and interaction between cortical regions in 30 patients with juvenile myoclonic epilepsy and 26 healthy controls. With increasing cognitive demand, patients showed increasing coactivation of the primary motor cortex and supplementary motor area. This effect was stronger in patients still suffering from seizures, and was not seen in healthy controls. Patients with juvenile myoclonic epilepsy showed increased functional connectivity between the motor system and frontoparietal cognitive networks. Furthermore, we found impaired deactivation of the default mode network during cognitive tasks with persistent activation in medial frontal and central regions in patients. Coactivation in the motor cortex and supplementary motor area with increasing cognitive load and increased functional coupling between the motor system and cognitive networks provide an explanation how cognitive effort can cause myoclonic jerks in juvenile myoclonic epilepsy. The supplementary motor area represents the anatomical link between these two functional systems, and our findings may be the functional correlate of previously described structural abnormalities in the medial frontal lobe in juvenile myoclonic epilepsy.

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Motor cortex coactivation correlates with disease activity and treatment. (A) Activation in the left central region in ‘2-back minus 0-back’ contrast was stronger in patients with JME with more active disease. The section on the left shows voxels, negatively correlated with time since last seizure (uncorrected, P < 0.05). Crosshair indicates voxel for which correlation is plotted on the right (R = −0.49). (B) Post hoc analysis of drug effects indicates a specific effect of valproate in JME. Left central activation decreased with increasing daily valproate dose (uncorrected, P < 0.05, R = −0.52). (C) Activity within the typical bilateral frontal and parietal working memory network, on the other hand, correlated positively with valproate dose, indicating a normalizing effect of valproate on the cortical activation pattern in JME (C, uncorrected, P < 0.05, R = 0.63).
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Figure 2: Motor cortex coactivation correlates with disease activity and treatment. (A) Activation in the left central region in ‘2-back minus 0-back’ contrast was stronger in patients with JME with more active disease. The section on the left shows voxels, negatively correlated with time since last seizure (uncorrected, P < 0.05). Crosshair indicates voxel for which correlation is plotted on the right (R = −0.49). (B) Post hoc analysis of drug effects indicates a specific effect of valproate in JME. Left central activation decreased with increasing daily valproate dose (uncorrected, P < 0.05, R = −0.52). (C) Activity within the typical bilateral frontal and parietal working memory network, on the other hand, correlated positively with valproate dose, indicating a normalizing effect of valproate on the cortical activation pattern in JME (C, uncorrected, P < 0.05, R = 0.63).

Mentions: The interval between the last seizure and the functional MRI scan ranged from 1 to 4500 days. Left motor cortex activation correlated negatively with duration of the seizure-free interval (Fig. 2A, voxels overlaid in sectional image thresholded at P < 0.05 uncorrected, correlation coefficient R = −0.49); i.e. greater motor cortex activation was seen in those with more recent seizures (no patient reported any myoclonic jerks during the experiments).Figure 2


Motor system hyperconnectivity in juvenile myoclonic epilepsy: a cognitive functional magnetic resonance imaging study.

Vollmar C, O'Muircheartaigh J, Barker GJ, Symms MR, Thompson P, Kumari V, Duncan JS, Janz D, Richardson MP, Koepp MJ - Brain (2011)

Motor cortex coactivation correlates with disease activity and treatment. (A) Activation in the left central region in ‘2-back minus 0-back’ contrast was stronger in patients with JME with more active disease. The section on the left shows voxels, negatively correlated with time since last seizure (uncorrected, P < 0.05). Crosshair indicates voxel for which correlation is plotted on the right (R = −0.49). (B) Post hoc analysis of drug effects indicates a specific effect of valproate in JME. Left central activation decreased with increasing daily valproate dose (uncorrected, P < 0.05, R = −0.52). (C) Activity within the typical bilateral frontal and parietal working memory network, on the other hand, correlated positively with valproate dose, indicating a normalizing effect of valproate on the cortical activation pattern in JME (C, uncorrected, P < 0.05, R = 0.63).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3102244&req=5

Figure 2: Motor cortex coactivation correlates with disease activity and treatment. (A) Activation in the left central region in ‘2-back minus 0-back’ contrast was stronger in patients with JME with more active disease. The section on the left shows voxels, negatively correlated with time since last seizure (uncorrected, P < 0.05). Crosshair indicates voxel for which correlation is plotted on the right (R = −0.49). (B) Post hoc analysis of drug effects indicates a specific effect of valproate in JME. Left central activation decreased with increasing daily valproate dose (uncorrected, P < 0.05, R = −0.52). (C) Activity within the typical bilateral frontal and parietal working memory network, on the other hand, correlated positively with valproate dose, indicating a normalizing effect of valproate on the cortical activation pattern in JME (C, uncorrected, P < 0.05, R = 0.63).
Mentions: The interval between the last seizure and the functional MRI scan ranged from 1 to 4500 days. Left motor cortex activation correlated negatively with duration of the seizure-free interval (Fig. 2A, voxels overlaid in sectional image thresholded at P < 0.05 uncorrected, correlation coefficient R = −0.49); i.e. greater motor cortex activation was seen in those with more recent seizures (no patient reported any myoclonic jerks during the experiments).Figure 2

Bottom Line: With increasing cognitive demand, patients showed increasing coactivation of the primary motor cortex and supplementary motor area.This effect was stronger in patients still suffering from seizures, and was not seen in healthy controls.Furthermore, we found impaired deactivation of the default mode network during cognitive tasks with persistent activation in medial frontal and central regions in patients.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK.

ABSTRACT
Juvenile myoclonic epilepsy is the most frequent idiopathic generalized epilepsy syndrome. It is characterized by predominant myoclonic jerks of upper limbs, often provoked by cognitive activities, and typically responsive to treatment with sodium valproate. Neurophysiological, neuropsychological and imaging studies in juvenile myoclonic epilepsy have consistently pointed towards subtle abnormalities in the medial frontal lobes. Using functional magnetic resonance imaging with an executive frontal lobe paradigm, we investigated cortical activation patterns and interaction between cortical regions in 30 patients with juvenile myoclonic epilepsy and 26 healthy controls. With increasing cognitive demand, patients showed increasing coactivation of the primary motor cortex and supplementary motor area. This effect was stronger in patients still suffering from seizures, and was not seen in healthy controls. Patients with juvenile myoclonic epilepsy showed increased functional connectivity between the motor system and frontoparietal cognitive networks. Furthermore, we found impaired deactivation of the default mode network during cognitive tasks with persistent activation in medial frontal and central regions in patients. Coactivation in the motor cortex and supplementary motor area with increasing cognitive load and increased functional coupling between the motor system and cognitive networks provide an explanation how cognitive effort can cause myoclonic jerks in juvenile myoclonic epilepsy. The supplementary motor area represents the anatomical link between these two functional systems, and our findings may be the functional correlate of previously described structural abnormalities in the medial frontal lobe in juvenile myoclonic epilepsy.

Show MeSH
Related in: MedlinePlus