Can changes in cortical excitability distinguish progressive from juvenile myoclonic epilepsy?
OBJECTIVE
We used transcranial magnetic stimulation (TMS) to investigate whether there were any characteristic cortical excitability changes in progressive myoclonic epilepsy (PME) compared to juvenile myoclonic epilepsy (JME).


METHODS
Six patients with PME were studied. Motor threshold (MT) at rest and recovery curve analysis using paired-pulse stimulation at a number of interstimulus intervals (ISIs) was determined. Results were compared to those of 9 patients with chronic refractory JME and 10 with chronic well-controlled JME.


RESULTS
PME showed a marked increase in cortical excitability at all the long ISIs (p < 0.01), compared to refractory JME (effect sizes ranging from 1.4 to 1.9) and well-controlled JME (effect sizes ranging from 2.0 to 2.4). Significant differences at the short ISIs 2-5 ms were seen only on comparison with the well-controlled group (p < 0.05, effect size 0.6, 0.7). There were no significant differences in MTs of PME compared to either JME groups.


CONCLUSIONS
Our findings demonstrate specific differences in cortical excitability using TMS between PME and those with JME, particularly at long latencies in the paired-pulse paradigm, implicating a role for γ-aminobutyric acid (GABA)(B) -mediated networks.
Badawy
Radwa A B
RA
Department of Neurology, Austin Health, Heidelberg, Victoria, Australia.
Macdonell
Richard A L
RA
Jackson
Graeme D
GD
Berkovic
Samuel F
SF
D000328:Adult; D000927:Anticonvulsants / Q000627:therapeutic use; D002540:Cerebral Cortex / Q000503:physiopathology; D002908:Chronic Disease; D003937:Diagnosis, Differential; D004351:Drug Resistance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D020191:Myoclonic Epilepsies, Progressive / Q000175:diagnosis* / Q000188:drug therapy / Q000503:physiopathology; D020190:Myoclonic Epilepsy, Juvenile / Q000175:diagnosis* / Q000188:drug therapy / Q000503:physiopathology; D050781:Transcranial Magnetic Stimulation / Q000379:methods / Q000706:statistics & numerical data*; D020194:Unverricht-Lundborg Syndrome / Q000175:diagnosis / Q000503:physiopathology; D005680:gamma-Aminobutyric Acid / Q000502:physiology
D000927:Anticonvulsants; D005680:gamma-Aminobutyric Acid