A prospective case-control study to develop biomarkers for individualised visual perturbation responses in epilepsy patients

This study involves analysing brain electrical activity (EEG), during administration of intermittent photic stimulation. This will involve a single one hour session, with 5 stimulation blocks and a 5 minute rest in between each block. This is administered by experienced hospital staff at the Neurology Department of St Vincent's Hospital Melbourne. During the session, you will be asked to sit on a comfortable chair, and your head will be measured with a measuring tape to determine the correct placement of the electrodes. The technician will then use a small amount of gel to attach the electrodes to your scalp. While the gel may feel slightly cool, it will not be uncomfortable. The gel helps to conduct the electrical signals from the brain to the electrodes. Electrodes will also be placed on the chest to record your heart rate. Once all the electrodes are in place, the technician will connect them to an EEG machine that will record the electrical activity. Setting up the electrodes initially should take no longer than 10-20 minutes. After the test, the electrodes will be removed from the scalp, and any remaining gel will be wiped away. After setting up the electrodes, you will receive photic stimulation – viewing a flashing light – while your brain’s electrical activity is being recorded with an EEG machine. This procedure is usually called Intermittent Photic Stimulation (IPS), though we will instead be using a very similar, but extended protocol called Randomised and Repeated Intermittent Photic Stimulation (RRIPS). In routine IPS, photic stimulation involves a series of 10s flashing lights in an increasing frequency (the speed of flashing) order. If a photo-paroxysmal response (PPR: brain waves caused by photic stimulus that are associated with seizures) is observed on the EEG, stimulation frequencies are then presented in decreasing (slower) order. This is because the aim of routine IPS is to determine whether someone is photosensitive (light sensitive) or not, and the frequency range that causes a PPR. In comparison, we will use the RRIPS protocol, where the photic stimulation frequency order is instead randomised. This is so we can remove any speed order effects which may occur, so that we know responses are not due to increasing or decreasing stimulation frequency. Also, instead of just one stimulation block, we will have 5 blocks. This is so we have multiple repeated examples for each stimulation frequency, to confirm that responses are consistent when repeated. If PPR is observed on the EEG, the photic stimulation round will be ceased and a break will be initiated for at least 5 minutes, before continuing with the stimulation block. The same procedure is administered for all participants.