The brain, which identifies who we are as individuals, remains our most delicate organ. With the average human lifespan progressively increasing, it is very likely that brain health will become the rate-limiting step for determining longevity and quality of life for the elderly. One major way that the health of our brains can be affected is by any type of unexpected acute brain injury: traumatic brain injury, stroke, brain hemorrhage, cardiac arrest-induced brain ischemia or other emergency situations. When an acute brain injury occurs, it is paramount to protect further neurological deterioration, act proactively to treat the underlying cause, and support the brain’s acute and chronic recovery. As a critical care neurologist, my job is to do precisely this for patients in the emergency room and the neuro-intensive care unit. The best feedback a clinician can currently obtain regarding the brain’s function is the neurological exam: whether the patient is awake, can comprehend and speak, and can move his/her body parts appropriately. Most patients with a severe acute brain injury are in a coma or have minimal consciousness. For such patients, timely diagnosis can become guesswork. In some cases, CT or MRI scans can assist in diagnosis, but transporting unstable patients on life support for these scans carries risks. While the spatial resolution of portable CT scans is improving, CT and MRI scans lack the temporal resolution to closely monitor acute brain injury. In addition, the scans cannot be performed with high frequency because of cost, difficulty in transportation and (for CT) risk of overexposure to harmful radiation. Multiple studies have shown that monitoring the brain continuously can improve the neurological outcome after acute brain injury. However, there remains a critical unmet need for continuous bedside monitoring tools capable of real-time diagnosis and feedback. Photonics can help meet this need, as well as strengthen the initial diagnoses in the critical first few moments and hours following a brain injury. Brain monitoring involves measurement of cerebral electrical activity (to determine whether neurons are firing properly), cerebral blood flow (CBF), intracranial pressure (ICP; pressure inside the brain while it is contained by the skull), and metabolic activity of brain cells. While cerebral electrical activity can often be done by noninvasive electroencephalogram (EEG) monitoring despite some limitations, the vast majority of brain monitors are invasive, causing many challenges to both clinicians and patients. Traditionally, measurements of CBF, ICP and metabolic activity have required drilling a small hole into the skull and introducing a device onto the surface or inside the brain. Photonic devices have shown increasing potential to provide minimally invasive and noninvasive brain monitoring. Indeed, noninvasive CBF monitors utilizing near-infrared spectroscopy (NIRS) technology are commercially available. And, fortunately, noninvasive ICP monitors utilizing NIRS and diffuse correlation spectroscopy (DCS) are being developed. These photonic devices allow brain monitoring similar to how we currently apply a pulse oximeter to a patient’s finger to measure tissue oxygen saturation. They allow for continuous brain monitoring without invasive techniques. But they also promise to improve outcomes at the earliest stages of treatment by enabling effective intervention and treatment during the critical first few minutes and hours following acute brain injury. The creation of noninvasive monitors means that a paramedic in the field may be able to apply a photonic device to the head of a patient, allowing rapid diagnosis of an acute brain injury without having to wait until the patient arrives to the hospital and receives a CT or MRI. After the patient is hospitalized, this means continuous monitoring of the brain to minimize evolving brain injury, allowing clinicians to alter CBF as needed, administer critical medication and offer emergency surgery (endovascular or open craniotomy). With time, I envision that all of the important brain function parameters — including CBF, ICP, metabolism and electrical activity — will be rapidly measured in a noninvasive way by medical professionals who may not necessarily be neurological experts. But to achieve this milestone, we need the photonics community to come together with clinical neuroscientists to work closely and synergistically toward developing technologies designed for these unmet needs. Together, we can help protect and treat our most delicate bodily organ, the organ that defines us as individuals. Meet the author Yama Akbari, M.D., Ph.D., is a board-certified neurologist with specialty training in critical care neurology and an assistant professor of neurology and neurological surgery at UC Irvine. His research laboratory is designed to mimic the neuro-intensive care unit with a focus on improving neurological recovery after severe brain injury. He collaborates closely with professors Bruce Tromberg and Bernard Choi at the UC Irvine Beckman Laser Institute to help address unmet needs in neurocritical care. The views expressed in Biopinion are solely those of the author and do not necessarily represent those of Photonics Media. To submit a Biopinion, send a few sentences outlining the proposed topic to marcia.stamell@photonics.com. Accepted submissions will be reviewed and edited for clarity, accuracy, length and conformity to Photonics Media style.