Epileptic Seizure Suppression by Focal Brain Cooling With Recirculating Coolant Cooling System: Modeling and Simulation

Abstract

A focal brain cooling system for treatment of refractory epilepsy that is implantable and wearable may permit patients with this condition to lead normal daily lives. We have developed such a system for cooling of the epileptic focus by delivery of cold saline to a cooling device that is implanted cranially. The outflow is pumped for circulation and cooled by a Peltier device. Here, we describe the design of the system and evaluate its feasibility by simulation. Mathematical models were constructed based on equations of fluid dynamics and data from a cat model. Computational fluid dynamics simulations gave the following results: 1) a cooling device with a complex channel structure gives a more uniform temperature in the brain; 2) a cooling period of <10 min is required to reach an average temperature of 25.0 • C at 2 mm below the brain surface, which is the target temperature for seizure suppression. This time is short enough for cooling of the brain before seizure onset after seizure prediction by an intracranial electroencephalogrambased algorithm; and 3) battery charging would be required once every several days for most patients. These results suggest that the focal brain cooling system may be clinically applicable.

Optimal Design of Neuroprotective Focal Brain Cooling Device Using Surrogate Model Approach

“…Thus, up to 2 mm below the brain surface should be cooled [13]. Ensuring that up to 2 mm from the surface of the brain is cooled is an essential point of treatment; however, we confirmed that the temperature 2 mm below the brain surface reaches the target temperature when the brain surface becomes the target temperature [14]. Thus, in this study, we focus not on the temperature 2 mm below the brain surface, but on the brain surface temperature.…”

“…The brain surface region just below the cooling device was 20 × 20 mm, which was divided into (50 × 50)-point grids for temperature measurement. Since we have confirmed that it takes less than 600 s to cool the brain to the target temperature, the simulation was run from the start of cooling (0 s) to 900 s, which we considered to be sufficient time for the brain surface temperature to reach the steady-state [14]. The sampling rate was 2 s. The total number of meshes in the FE simulation was about 400,000, which is within a range we have confirmed not to affect simulation results.…”

“…The wearable FBC system under development consists of a cooling device made of titanium, with a water channel inside, embedded in the skull, a recirculating coolant apparatus, and a battery, as shown in Fig. 1 [14]. The coolant is cooled outside the body, flows into a cooling device directly attached to the brain, removes heat from the brain, and is then cooled again outside the body by the recirculating coolant apparatus.…”

“…Animal and clinical studies are required for designing the cooling device and validating its cooling performance; however, it is not realistic to perform many experiments due to ethical problems as well as cost and time burden. Hata et al developed finite element (FE) simulation models of the FBC system to reduce the number of animal and clinical experiments [14]. A complex FE simulation takes several hours, sometimes days, to perform one simulation run.…”

“…The frequency of battery charge is a key performance indicator of the FBC because frequent charging or exchanging of the battery is undesirable. Hata et al estimated the energy consumption of the FBC system and showed that charging or exchanging of the battery would usually be required every few days in patients with temporal lobe epilepsy [14]. This frequency of required battery charging does not detract from the usability of the FBC system.…”