A key contributor to outcome following a stroke or a traumatic brain insult is the development of secondary brain injury. This is a process of more damage to brain tissue that occurs over a number of hours and days after the original event. Currently, there is little we can do to restore normal working in brain regions that have been damaged beyond repair by the initial trauma or stroke. However, we might be able to prevent secondary brain injury if we were able to detect this as it progresses. After an injury, a region of vulnerable but still potentially viable brain tissue is established around the injury core. This is the region that is susceptible to secondary brain injury and is called the 'penumbra'. We now know that electrical brain waves, called "spreading depolarisations" (SD), frequently occur in the penumbra after an injury. We believe a special class of these SDs to be very harmful and to contribute significantly to the process of secondary injury. However, there is another group of SDs that bring with them an extra supply of oxygen and glucose. This can be very beneficial to the neurons in the penumbra in helping them to recover. As such, whilst we would like to prevent SDs that are harmful, we do not want to prevent those that might be favourable. The problem is, we currently have no way of telling the difference between them. One way we might be able to tell the difference though is to examine the effect they have on the health of the neurons. Over the last few years I have worked to develop a method to probe neuronal health and to monitor changes in the viability of the neurons in real-time. Now I would like to use this method to characterise the changes that indicate declining neuronal viability. This would enable us to see secondary brain injury happening live at the patient's bedside, giving us a much better opportunity to intervene before it is too late. I would also like to use this method to identify which SDs are causing harm to the neurons and which ones are potentially helping them recover. This would mean that we could personalise treatments for patients experiencing harmful SDs. Furthermore, because even just one harmful SD will likely damage or kill neurons in the penumbra we would ideally like to prevent them from happening at all. This would mean though, that we would have to identify the changes that make neurons vulnerable only to harmful SDs. Luckily, we know from pre-clinical experiments that there are some very specific changes in the tissue environment that predispose neurons to harmful SD. Importantly, these changes are not seen before those that might be beneficial. As a part of the work I have done in developing a method to probe neuronal health, I have also established a way of assessing changes in the tissue environment that predispose neurons to harmful SDs. I would like to use this method to see if I can predict which patients are likely to begin having harmful SDs. This would mean that in the future, instead of waiting for them to start we could give pre-emptive treatments to susceptible patients. Finally, in order to actively prevent secondary brain injury, we need to know both when neuronal health is in decline and also what treatments are effective in improving this. By continuously tracking neuronal health status in real-time I aim to provide physicians with an online bedside tool that will both identify declining health and provide immediate feedback on the effectiveness of therapeutic interventions. The implementation of such a tool into clinical practice has the potential to limit the amount of secondary brain damage that occurs after an injury and thereby to significantly improve the outcome of the patients.