Concussions, often labeled as “mild” traumatic brain injuries, are anything but mild in their impact. These injuries, which result from a blow to the head or body, can disrupt the function of multiple physiological systems. One of these systems is the autonomic nervous system (ANS). Because the ANS plays a role in so many aspects of our health and function, disruption of its delicate balance can lead to a wide range of symptoms, as well as impair crucial neurological functions, including the pupillary light reflex (PLR). In this article, we’ll delve into the intricate interplay between the ANS, PLR, and concussions, exploring the importance of understanding ANS health and utilizing PLR to help implement effective strategies for concussion assessment and rehabilitation.

Understanding the Autonomic Nervous System (ANS)

The ANS serves as the body’s autopilot system, regulating myriad involuntary functions essential for survival. Made up of the sympathetic and parasympathetic branches, the ANS maintains homeostasis by dynamically adjusting physiological processes in response to internal and external stimuli. These responses are the “fight, flight, freeze” responses many people are familiar with. From heart rate and blood pressure to digestion and immune responses, the ANS plays a pivotal role in ensuring optimal bodily function. This wide-reaching role is how so many seemingly unrelated symptoms can actually be related and why assessing the ANS is a key part of evaluating concussions.

The Impact of Concussion on the Autonomic Nervous System:

Concussions disrupt the delicate balance of the ANS, leading to dysregulation of autonomic function. Following a concussion, the sympathetic branch of the ANS often becomes overactive, resulting in symptoms such as increased heart rate, blood pressure fluctuations, and heightened stress responses. On the other hand, the parasympathetic branch may exhibit impaired function, leading to issues such as dizziness, fatigue, and gastrointestinal disturbances. Both of these can occur at the same time within the same person. This makes objective measures of ANS dysfunction crucial for comprehensive concussion management and rehabilitation.

Assessing Autonomic Function: The Role of Pupillary Light Reflex (PLR)

The pupillary light reflex (PLR) serves as a valuable tool for assessing autonomic function, particularly in the context of concussions. PLR involves the constriction/shrinking or dilation/widening of the pupils in response to changes in light intensity. The speed, duration, and amplitude of this reflex are all controlled by the ANS. Following a concussion, abnormalities in PLR responses may manifest as changes in pupil size, asymmetry between pupils, or delays in response time. These alterations in PLR can provide valuable insights into the severity of the concussion and guide treatment decisions.

Utilizing PLR in Concussion Assessment

Incorporating PLR assessments into concussion evaluations can enhance diagnostic accuracy and inform treatment strategies. Objective measurements of PLR parameters, such as pupil size, latency, and constriction velocity, can complement subjective assessments and aid in monitoring recovery progress over time. Advanced technologies, such as pupillometry, offer precise quantification of PLR responses, allowing for early detection of autonomic dysfunction and tailored interventions.

Rehabilitating Concussions: A Comprehensive Approach

Effective concussion rehabilitation requires a multidisciplinary approach that addresses both physical and neurological aspects of injury. In addition to traditional symptom management protocols, interventions targeting ANS dysregulation and PLR abnormalities can play a pivotal role in promoting recovery. Various therapies offer promising avenues for optimizing ANS function and restoring neurological integrity following concussion. These include acupuncture, breathwork, biofeedback, and vestibular rehabilitation. Structured heart rate-based cardiovascular activity is also a great approach for supporting ANS function and concussion rehabilitation. For more guidance on how to use your favorite cardio exercise to address acute or persistent concussion symptoms, download this free worksheet.

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*PLEASE NOTE: this self-guided exercise is a safe and effective way to begin your recovery, but is NO replacement for professional care. If you’ve been injured or are experiencing persistent post concussion symptoms, please seek help from a specialist. If you need help finding resources in your area, email Jackupuncture.*


Concussions pose significant challenges to both athletes and non-athletes alike, highlighting the importance of understanding the complex interplay between the autonomic nervous system, pupillary light reflex, and concussion pathology. Leveraging PLR in concussion assessment and rehabilitation enhances diagnostic accuracy, improves treatment outcomes, and ultimately facilitates safe return to activity for individuals recovering from concussions. As part of our ANS assessment, we use ReflexPro pupillometry at Jackupuncture. This helps us not only assess PLR for concussion evaluation, but also monitor ANS function over time to ensure patients are responding to treatment and progressing well through rehabilitation. Thanks to pupillometry innovations like ReflexPro, we can provide PLR assessments in the clinic or anywhere our patients are with a mobile app, making concussion evaluation and rehabilitation more accessible.