A team of researchers from Yamaguchi University in Japan has submitted a patent application for an implantable brain cooling device that would be used to develop a new treatment for severe cases of epilepsy.
Epilepsy is a condition that is characterised by abnormal electrical activity in the brain. Many epileptics experience seizures, during which they convulse – sometimes violently – before losing consciousness. These seizures are caused by an “electrical storm” of abnormal neuronal activity that spreads from the locus (or point of origin) to adjacent tissue.
The brain cooling device is based on the principle that this frenzied activity of cells results in overheating of adjacent areas of the brain, which in turn causes cells in those areas to become overactive themselves, so that the abnormal activity spreads across the cortical tissue.
The device is a small thermoelectric heat pump similar to the one below. It consists of two ceramic plates containing semiconductor wafers that would be implanted into the cerebral cortex, at the focal point of abnormal activity associated with the seizures. This pump would collect excess heat from the surface of the brain, and transfer it to a heat sink.
The device is designed to detect the abnormal activity associated with seizures and switch on the pump in response. This causes a rapid increase in the temperature of one of the wafers. Continual transfer of this heat to a sink embedded in the skull on the outside causes rapid cooling of the other wafer. This reduces the temperature of the brain tissue into which the implant is embedded to about 20 degrees Celcius; the tissue is temporarily inactivated, and the abnormal electrical activity ceases.
These devices were initially developed for the computer industry, where they are used to control the temperature of microprocessors. The first in vivo animal studies in which they were used were carried out in 2001 by Steven Rothman and Xiao-Feng Yang of the Department of Neurology at Washington University School of Medicine in St. Louis, Missouri, who found that the device could abolish drug-induced seizures in rats within 10 seconds if activated at the time of seizure onset.
About 60% of epileptics have some kind of focal epilepsy, and 15% of these patients do not respond to anti-convulsant medications. Such patients have few options – for example, a surgical procedure called a hemispherectomy (which involves the removal of an entire hemisphere of the brain) can be performed as a last resort.
Local cooling was first recognized as being of potential benefit to epileptics about 100 years ago. With thermoelectric devices, the method could in the near future provide an alternative to the drastic surgical procedures currently used to treat patients with intractable epilepsy.
Researchers have been testing these devices in primates for about two years. If the Japanese team’s application is granted, human clinical trials could be commenced soon. Rothman and Yang envision a hand-held device for intraoperative cooling of the brain by the end of the decade.
Rothman, S. & Yang, X.-F. (2003). Local cooling: A therapy for intractable epilepsy. Epilepsy Curr. 3: 153-156. [Full text]