MTL Annual Research Report 2011

Figure 1: Simplified system block diagram.

Epilepsy is a common chronic neurological disorder that affects about 1% of the world population ^[1] . It is characterized by repeated seizures, which are caused by an abnormal neuronal firing rate of the affected brain area. One way to detect a seizure is through an electroencephalogram (EEG), which is the recording of the electrical activity produced by the firing of neurons in the brain. Continuous EEG recording is extremely important for patients with epilepsy because doctors cannot only track the number of seizures the patient has, but also have access to the recordings during the attacks which allows doctors to determine the efficacy of the treatment.

The most common EEG recording place is at the scalp; however, it can also be obtained at the skull (subdermal) or at the brain (subdural). Continuous EEG recordings through measurements at the scalp require that the patient wears an external medical device at all times, which can be extremely inconvenient. One way to solve this problem is to implant the medical device. A subdural EEG implant would require a very complex surgery, so we have decided to do a subdermal EEG and avoid such complications. Our minimally invasive implant will be placed between the scalp and the skull behind the right ear, and the electrodes will run to the front part of the skull.

Our system consists of 2 EEG channels sampled at approximately 250 Hz with a 12-bit resolution. Figure 1 shows the simplified system block diagram.