Examining Objective Concussion Monitoring in Collegiate Athletes

Sports neurology is an evolving subspecialty of neurology dedicated to the evaluation, diagnosis, and management of neurologic conditions related to athletic participation. Clinicians in this field employ a comprehensive neurologic approach that encompasses acute injury assessment, return-to-play decision-making, long-term brain health monitoring, and multidisciplinary care in collaboration with sports medicine, rehabilitation, and neuropsychology specialists. Neurologists have become increasingly integral to concussion management as the understanding of biomechanics, pathophysiology, and individualized recovery trajectories in athletes grows, and fellowship training programs are expanding to meet this need. The goal of sports neurology is to optimize neurologic outcomes while safely supporting athletes’ continued participation in sport and physical activity.¹

With the subspecialty on the rise over the last decade, more studies have emerged in the field of sports neurology. Among those at the forefront of this research is Kyle Marden, MD, a sports neurologist at Northwestern Medicine. Marden is the lead study author on a presentation titled “Feasibility of Pupillometry in Concussion Diagnosis and Recovery Monitoring in Collegiate Football Athletes” that was recently published in BMJ Journals. For context, the study evaluated pupillometry as a concussion assessment in collegiate football players and found that pupillometry shows promise as an objective tool for concussion evaluation.

To gain further insight, NeurologyLive spoke with Marden, who also serves as an assistant professor of neurology at the Feinberg School of Medicine at Northwestern University, about his recent research. In the Q&A, he discussed efforts to introduce more objective, physiology-based tools into concussion care, the feasibility of sideline implementation, and how this approach may help inform recovery and return-to-play decisions. Martin also reflected on the broader direction of sports neurology and the growing emphasis on multimodal strategies to better assess and manage brain injury in athletes.

NeurologyLive: Can you provide an overview of your role as a sports neurologist?

Kyle Marden, MD: My role sits at the intersection of acute injury care and long-term brain health. I evaluate and manage concussions and symptoms like post-traumatic headache, along with peripheral nerve injuries and other neurologic conditions affecting athletes. A big focus of mine is building centers of care. Currently at Northwestern Medicine, we’re developing a multidisciplinary concussion program that combines neurological evaluation, rehabilitation therapies, neuropsychology, and a structured return-to-activity pathway. I’m also involved in team coverage with Northwestern University athletics, as well as education for athletes, coaches, and the broader community.

Let’s focus on your recent publication. What were the main takeaways or key findings?

A key takeaway is that quantitative pupillometry is feasible in a real collegiate football environment. It’s quick, portable, and practical, both on the sideline and in the clinic. Within that framework, we found that dynamic pupil response measures — especially minimum diameter at peak constriction — appear more informative than static pupil size. These reflect autonomic and oculomotor pathways that can be affected after a concussion.

We also observed meaningful baseline variability within athletes that defines a physiological noise floor and reinforces that pupillometry should be interpreted longitudinally rather than using single cutoffs. Overall, pupillometry shows a physiologic signal after concussion, but that signal has to be understood within normal variability and individual trends.

Why did you and your colleagues feel conducting research of this nature was important?

Concussion diagnosis is still largely symptom-driven, which introduces subjectivity. Athletes may underreport symptoms, and clinicians lack physiologic measures that directly reflect brain function. The pupillary light reflex offers a rapid, noninvasive window into brainstem and autonomic networks. Demonstrating feasibility is the first step toward using this physiology in clinical monitoring. This is part of a broader effort to see whether pupillometry can support diagnosis and track recovery over time.

What were some of the limitations of this study?

The main limitation was sample size, especially in the concussed group, so we can’t define diagnostic thresholds yet. Measurements are also susceptible to external factors — lighting, fatigue, exertion, circadian effects, and even the device used and its positioning on the eye can influence results. Concussion itself is heterogeneous, and pupillometry captures only one physiologic domain, so It needs to be part of a multimodal approach. Those limitations help shape the next phase of our research.

What needs to be studied further?

The next steps focus on understanding the signal and then integrating it into care. That includes defining normal variability and individual noise floors, determining whether early pupillary changes predict prolonged recovery or specific symptom phenotypes, and using multiparameter analytic approaches rather than relying on a single metric. That may mean combining multiple domains within pupillometry. And lastly, comparing findings across different sports and even against non-athlete controls.

What do these findings mean for student-athletes and for the broader field of sports neurology?

For athletes, this represents progress toward more objective monitoring of brain function after concussion and potentially more individualized recovery decisions. For the field overall, it reflects a shift toward physiology-informed care. Feasibility studies like this help move promising tools into real athletic settings. Pupillometry most likely won’t be a standalone test, but it could be one piece of a multimodal framework to diagnose injury and track recovery.

Is there anything else about your presentation or the field in general that you’d like to add?

Overall, the future of sports neurology isn’t a single concussion test — it’s multiple physiologic signals coming together, and pupillometry may be one piece of that puzzle. I’d also highlight the advantages of having a sports neurologist on the sidelines or in the clinic. We combine expertise in brain function and peripheral nerve function and are available to support our sports medicine and primary care colleagues in caring for athletes — whether they’re high school athletes, professional athletes, or even weekend warriors. Our goal is to help our colleagues treat these athletes and return them to activity — or even to work — as quickly and safely as possible.

Transcript edited for clarity.

REFERENCES
1. Zafonte R, Pascual-Leone A, Baggish A, et al. Sports neurology: An emerging subspecialty. Neurology. 2014;83(21):1926-1932. doi:10.1212/WNL.0000000000001011