Abstracts

Rationale: The few days before and after birth are a time of special risk for stroke in infant, probably related to activation of coagulation mechanisms. Arterial ischemic stroke around the time of birth is recognised in about 1/4000 full-term infants. Neonatal seizures are most common clinical finding that triggers assessment. In other children, perinatal stroke is recognised only retrospectively, with emerging hemiparesis or seizures after the early months of life. Our aim is to elucidate whether photothrombic stroke induced in period before initial jump in EEG development can induce epileptogenesis. Methods: To find an age of rapid development of EEG activity immature rats at postnatal days 7, 9, 12 and 15 were anaesthetized with isoflurane and implanted with epidural EEG silver electrodes. In order to distinguish between behavioral states EMG bipolar steel electrodes were placed in extracellular space of nuchal muscles. After recovery period (~2h) animals were connected to the experimental system and Video-EEG + EMG was recorded for 30minutes. After energy and entropy analysis of EEG we selected age P7 for further experiments. After intravenous application of Bengal Rose (BR, 2mg/ml, 0.15ml per animal) the exposed skull above left motor cortex was illuminated with concentrated beam from high power green laser (50mW, Roithner Laser, Austria) for 5 minutes with 0.1s on/off cycle. To assess motor deficits rotarod and bar holding test was performed 2months after the stroke. The animals then underwent implantation of EEG cortical and hippocampal electrodes and after 1 week of recovery they were continuously Video-EEG monitored for 5 consecutive days. The animals were then overdosed with urethane and transcardially perfused and the brains cut in 50um slices for further histological staining. Results: Analysis of spontaneous EEG activity during development revealed biphasic rhytmogenesis. Both Shannon entropy and energy of the signal have risen with age. However, highest increase was in the interval P7 to P9 and P12 to P15 respectively while P9 to P12 period remains stable. Thus for further experiments we have used P7 animals to induce ischemic stroke before first developmental jump in EEG genesis. The ischemic photothrombic lesions in experimental animals penetrated whole thickness of the motor cortex frequently reaching external capsule or cerebral ventricle. The diameter of the lesion was 2.4 -3.7 mm. Motor skills were tested using rotarod and bar holding test. Rotarod nor barholding test did not reveal significant change in latency, however, detail analysis of the step cycle on rotarod with high resolution video revealed changes in forepaw and shoulder blade posture during stance and swing phase on contralateral side. Preliminary results of video EEG monitoring has shown partial hippocampal seizures with secondary generalization. Conclusions: Our results suggests that perinatal cortical ischemic lesion induces epileptogenesis in rats. The project was supported by grant from the Academy of Sciences of the Czech Republic number 1QS501210509.