DECREASED GABA[sub]B[/sub]-ERGIC INHIBITION IN THE IPSILATERAL MOTOR CORTEX IN FOCAL EPILEPSY
Abstract number :
2.175
Submission category :
Year :
2003
Submission ID :
3886
Source :
www.aesnet.org
Presentation date :
12/6/2003 12:00:00 AM
Published date :
Dec 1, 2003, 06:00 AM
Authors :
Hajo M. Hamer, Janine Reis, Hans-Helge Mueller, Katja Hattemer, Wolfgang H. Oertel, Felix Rosenow Epilepsy Center - Dept. of Neurology, University of Marburg, Marburg, Germany; Medical Biometry and Epidemiology, University of Marburg, Marburg, Germany
It is unclear whether focal epilepsies influence the processing of cortex distant of the epileptogenic zone. In this study, possible changes in the motor cortex were analyzed in patients with temporal and extratemporal epilepsies.
Single and paired-pulse transcranial magnetic stimulation (TMS) was applied to 20 healthy controls and to 24 patients with focal epilepsy (38.3 + 13.2 years; 12 right, 12 left, 14 temporal, 9 extratemrporal: 5 frontal, 1 central, 2 parieto-occipital; 1 fronto-temporal) ipsi- and contralateral to the epileptogenic zone. The active and resting motor threshold (MT), the cortical silent period (CSP), the intracortical inhibition (ICI; interstimulus intervals (ISI) 2 and 3ms) and the intracortical facilitation (ICF; ISI 10 and 15ms) were determined. The measures obtained ipsilateral to the epileptogenic zone were compared to the contralateral hemisphere and to controls using non-parametric tests including Hodges-Lehmann estimates of median differences (HLE).
The CSP elicited in the ispilateral motor cortex (median: 163.2ms) was shorter as compared to the contralateral CSP (median: 177.5ms; HLE: 17.5ms; confidence intervall (CI): 7.7-28.4ms; P=0.001). This difference was more pronounced in extratemporal (HLE: 26.6ms; CI: -0.5-62.5ms) as compared to temporal epilepsies (HLE: 14.3ms; CI: 4.7-26.2ms). No significant differences were found between the ipsi- and contralateral MT, ICI or ICF (p[gt]0.05). There was a trend towards a shorter ipsilateral CSP as compared to controls (median 173.4ms; HLE: 11.4ms; P=0.17) in contrast to the contralateral CSP (HLE: -2.1ms; P=0.89).
Since the CSP reflects most likely GABA[sub]B[/sub]-ergic IPSP, the results suggest that focal epilepsies lead to a decreased GABA[sub]B[/sub] receptor mediated inhibition in the ipsilateral motor cortex even when the epileptogenic zone is distant to it. The modulation of this inhibtion appears to decrease with the distance of the epileptogenic zone.
[Supported by: Partially supported by the Ulran-professorship for Neurology/Epileptology]