Once upon a time in an ED not so very long ago, a patient who presented after a blow to the head was subjected to history and physical examination, and at the discretion of the examining physician, a CT scan of the brain. When the scan came back negative there was cause for relief. The patient was deemed lucky, advice was doled to avoid operating heavy machinery until the headache cleared, and everyone lived happily ever after ... or at least we thought they did.
Then along came the NFL, the lawsuits and the media. Almost overnight, awareness that concussion could have lasting effects dawned on the public. All of a sudden a condition with no clear definition, no diagnostic, and no validated treatment was recognized as having a potentially significant impact. All we knew for sure was that the problem was invisible: it could not be seen on CT. Without an accurate diagnostic it is almost impossible to know the incidence of the affliction or project how many patients seek care in an ED, primary care office or elsewhere. We also don't know how many suffer in obscurity, self-medicate or develop post-concussive syndrome, or how many recover fully.
Evaluation of conjugate eye movements has been a key component of the neurologic examination for at least 3500 years. Concussions are typically associated with post-traumatic vision problems, such as difficulty with reading, visual accommodation, and saccadic eye movements (rapid eye movements which refocus a peripheral image onto the central retina) [1,2,3,4,5]. Eye tracking dysfunction is one objective measure of concussion, but methods of tracking have not been well refined, and even so, require highly skilled examiners, and have never been translated into the ED environment. However, for more than 30 years, eye movement tracking technology has been widely used for marketing studies, video games, and neuropsychiatric research. We took advantage of the old and the new, and developed an eye-tracking tool that can objectively identify and quantify signs of concussion after injury, even at the initial ED evaluation.
Patients are seated in a chair, head on a chinrest, and look through a small aperture focused on a video screen. Imagine a patient seated at a Haag-Streit slit lamp -- only instead of looking straight ahead, the patient is looking at a music video (we used Shakira Waka Waka or K'NAAN Wavin'Flag) for 220 seconds. The aperture moves over a set trajectory along the video screen, and a computerized algorithm tracks binocular pupil movements in horizontal and vertical planes while the video plays and the aperture moves. The tracking tool then plots and quantifies eye tracking movements which we can distinguish as 'normal' or 'abnormal-concussion', as long as there were no pre-existing CNS or oculomotor abnormalities [6,7]. In addition, we can track concussion improvement through subsequent eye tracking tests [7].
What exactly will this mean for the ED physician, or more importantly, for the head-injured child or adult wheeled through the ED doors? Any new technology is likely to have a learning curve. Currently we are engaged with the FDA in the clearance process for our tracking technology. Once it is FDA-cleared, the tool will be available to EDs. But because there is currently no globally accepted definition, diagnostic or treatment for concussion, I would predict something more akin to a roller coaster. We know from our clinical studies conducted in the ED of Bellevue Hospital [7] that many people with head injuries have disrupted neuronal circuitry controlling eye movements even if the CT scan is negative. Does this mean eye tracking can detect all concussions? This depends on how you define concussion. The technology detects mass effect and neuronal pathway disruption. The technology is not a substitute for head CT scan where clinically indicated -- it only detects mass CNS lesions or blood if they are either causing mass effect or disruption. Tracking is an assessor of physiologic function whose nearest living relative is the exquisitely detailed optometric examination. It tells us how the brain feels, not how it looks. Most importantly it reveals when physiologic function is distressed.
For the patient with a possible brain injury, or for a concerned parent, this technology can either mean peace of mind, or create cause for additional concern. The advantage of being able to detect an injury, however, is that the efficacy of potential treatments can be measured. A recent editorial in the New England Journal postulated that the cause of 30 consecutive failed trials for brain injury might be inadequate classification of disease severity and lack of outcome measures [8]. The first step is admitting we have a problem. The next will be developing treatments for it.
For the ED doc, this tool might be a potential timesaver. The ability to identify concussion in < 3 minutes, without sedation, radiation or a needle inserted anywhere, almost sounds like something from a fairy tale. Once upon a time, a patient came into the ED with absolutely no indications for CT scan, and was sent home happy within an hour of triage, knowing he would be okay.
Visit the EP Monthly YouTube page to see this technology in action.
Uzma Samadani MD, PhD, FACS is the Co-Director at the Steven and Alexandra Cohen Veterans Center for Post-Traumatic Stress and Traumatic Brain Injury at NYU Langone Medical Center; Assistant Professor Departments of Neurosurgery, Psychiatry, Physiology and Neuroscience, New York University School of Medicine, New York; Chief Neurosurgeon New York Harbor Health Care System. A version of this article originally appeared at Emergency Physicians Monthly.