About one third of epilepsy sufferers are refractory to drug treatment. When drugs are ineffective, these people find their hope in brain-applied electrical stimulation. Several commercial neuroprosthetic devices have been successful in providing at least partial relief. They include a vagal nerve stimulator (VNS) from Cyberonics Inc., and a deep brain stimulator from Medtronic Inc., and cortical stimulation device from NeuroPace Inc. These devices are surgically implanted and cut the number of seizures in half or more in about 40% of drug-resistant patients. Currently, there is no neurological test to predict who will benefit from electrical stimulation. To solve this problem, Dr. Christopher DeGiorgio, a neurologist at UCLA, decided to use an external stimulator to estimate whether the epilepsy sufferers would benefit stimulation therapy before an invasive surgery is performed to implant a permanent device. His stimulator activates a superficially-located trigeminal nerve, a large cranial nerve that projects to key parts of the brain that modulate seizure and mood. The stimulation is applied at the forehead, while the electrode leads are connected to a small wearable pulse generator. According to the initial clinical test, the stimulator has similar efficacy to the implantable VNS. A positive side-effect of trigeminal nerve stimulation is an improvement in mood, which is important as many epilepsy patients suffer from depression. A startup company NeuroSigma Inc. has licensed the approach to stimulate the trigeminal nerve for epilepsy, depression, and PTSD, and is developing an implantable version for those who find relief with the externally-applied device.