Abstracts

Rationale: The cooling of brain tissue has been recognized to effectively suppress epileptiform discharges (EDs) and local brain cooling using a thermoelectric device has recently gained much attention since it has a potential to be a viable alternative for a surgical resection of epileptogenic foci. We have therefore developed an implantable focal cooling system including Peltier chips in order to automatically suppress epileptic seizures immediately after detecting EDs. However, when considering implantable systems , several problems such as the electric power supply or the arrangement of the whole system in the body have to be resolved. To resolve these problems, we developed a new cooling device with a heat pipe attached to the Pertier chip and also examined the performance of this device for the treatment of experimental neocortical seizures.Methods: We made a cooling device composed of a heat pipe and a Pertier chip with a heat sink. The heat pipe was a flat-type and the size was 100 x 5.3 mm in length and width and 2.0 mm thick. The size of the Pertier chip included a heat sink was 7.0 x 7.0 mm in length and width and 2.0 mm thick. One side of the heat pipe was exposed for the cortical cooling, while the Pertier chip was fixed to the other side of the heat pipe. The heat pipe between both sides was covered by heat insulation material. Experiments were performed on adult male Sprague-Dawley rats under halothane anesthesia. After performing a craniotomy (10x9 mm), one side of the heat pipe was placed on the surface of the cortex. A thermocouple and a needle electrode for recording electrocorticograms (ECoGs) were also placed just beneath the cooling site. Kainic acid (KA) was injected into the cooled cortex to provoke EDs. After confirming the appearance of EDs, the cortex was cooled by applying the current to the Pertier chip. We analyzed the changes in the temperatures and ECoGs during cooling.Results: After the KA injection, EDs appeared within 20 min and thereafter did not disappear spontaneously. Obvious amplitude reductions of EDs by local brain cooling were observed in all rats (n=5). The temperature of the cortical surface was maintained at 35.5 ± 0.4 °C before cooling and then decreased to below 25 °C within 15 seconds. We estimated the sequential changes of EDs by calculating the root-mean-squares (RMSs) of the ECoGs. The RMSs were significantly suppressed from 40 seconds and the slower components (0.5-8 Hz) of ECoGs also significantly decreased from 30 seconds after the start of cooling. After the temperature reached 25oC, the mean amplitude stayed low throughout the subsequent period.Conclusions: We developed a new focal cooling device with a heat pipe and a Pertier chip and confirmed its ability to successfully suppress EDs in an experimental seizure model. A cooling device with a heat pipe may therefore be the first step in developing a new type of implantable cooling system for the control of seizures in the future.