Abstracts

Rationale: Cooling of the brain tissue has been shown to effectively suppress epileptiform discharges (EDs). However, the influence of such cooling on the normal function and histology has not yet been thoroughly investigated. This study reports the neurophysiopathological consequences of focal cooling applied to terminate EDs.Methods: Experiments were performed on adult male Sprague-Dawley rats (250-350 g) under halothane anesthesia. A thermoelectric (Peltier) chip (6x6x2mm) was used as a cooling device and was placed on the surface of the sensorimotor cortex after a craniotomy (10 x 10mm). A thermocouple was then placed between the Peltier chip and the brain surface. Focal cooling of the cortex was performed at the temperatures of 20°C, 15°C, 10°C, 5°C, 0°C and -5°C for 1 hr (5 rats in each group), which are all temperatures shown to suppress EDs. Then the cranial window was repaired. Motor function was evaluated by the beam walking score (BWS) every day for 7 days. The rats were next either deeply anesthetized and sacrificed 7 days after the operation for a histological examination of the neural tissue following staining of the tissue sections with hematoxylin-eosin, the Klüver-Barrera and the TUNEL. Results: The BWS decreased on the day after cooling only in the -5°C group (p≤0.05), while the BWS did not change in the other temperature groups. Histologically, necrosis of the neurons and proliferation of the astrocytes were only observed in the -5°C group. Conclusions: Focal cooling of the cortex for 1 hour above a temperature of 0°C was thus found to be effective for the termination of EDs without any irreversible damage.