A head injury, medically categorized as a Traumatic Brain Injury (TBI), is often publicly associated with dramatic visual signs, such as a noticeable change in the size of the eyes’ pupils. This belief leads many people to incorrectly assume that without this visible symptom, a serious brain injury like a concussion has not occurred. Understanding the true relationship between pupillary changes and different severities of TBI is important for proper assessment and management. A concussion can happen even when the eyes appear completely normal, making reliable indicators of injury crucial.
The Relationship Between Pupils and Concussion Severity
A person can sustain a concussion, defined as a mild Traumatic Brain Injury (mTBI), without showing any sign of dilated pupils. Concussions involve a temporary disturbance in brain function, typically at a cellular or chemical level, and do not usually result in structural damage that affects pupil control. The pupillary light reflex is controlled by cranial nerves that pass through the brainstem, which is generally not compromised in an isolated mild concussion. Therefore, the absence of dramatic pupillary changes does not rule out a concussion.
Pupillary changes, especially one pupil becoming significantly larger than the other, are more indicative of a severe TBI (sTBI) or a complication like intracranial hemorrhage. These severe injuries cause swelling or bleeding within the skull, leading to increased intracranial pressure (ICP). This pressure can mechanically compress the oculomotor nerve, causing the pupil on the affected side to dilate and become non-reactive to light. While mTBI can cause subtle, temporary changes like a slowed pupillary light reflex, these are often only detectable with specialized equipment.
Recognizing Common Concussion Symptoms
Since pupillary signs are not a reliable marker for a mild injury, recognizing the spectrum of common concussion symptoms is the most helpful diagnostic tool. Concussion symptoms are typically grouped into physical, cognitive, and emotional categories, and they can manifest immediately or be delayed.
Physical Symptoms
Physical symptoms often include a headache that may feel like pressure, dizziness, problems with balance, and nausea or occasional vomiting. Individuals also report heightened sensitivity to light (photophobia) or noise (phonophobia), along with a general feeling of fatigue.
Cognitive Symptoms
Cognitive symptoms are often described as “brain fog,” involving feeling slowed down, dazed, or confused. An injured person may experience temporary memory issues, such as difficulty remembering the events surrounding the injury. They might also have trouble concentrating, focusing attention, or processing new information. These changes in thinking are a hallmark of the functional disruption caused by an mTBI.
Emotional and Sleep Disturbances
Emotional and sleep disturbances frequently accompany a concussion and may persist even after physical symptoms improve. Mood changes, such as increased irritability, anxiety, or sadness, are commonly reported. Changes to sleep patterns, including sleeping much more or having difficulty falling or staying asleep, are also characteristic. Any combination of these varied symptoms following a head impact warrants medical evaluation.
Warning Signs Requiring Immediate Medical Attention
Although a concussion itself does not typically cause dramatic pupillary changes, certain symptoms signal a medical emergency requiring immediate intervention. These “red flag” signs indicate a potential complication, such as a severe brain bleed or swelling. One of the most serious signs is anisocoria, where one pupil is noticeably larger than the other, suggesting dangerous pressure on the brainstem.
Other severe warning signs include a headache that continuously worsens and does not respond to pain relievers. Repeated or persistent vomiting, convulsions, or seizures are also major concerns. Any deterioration in consciousness, such as being unable to wake up, excessive drowsiness, or increasing confusion, signals an urgent need for professional care. Difficulty with speech, weakness or numbness in any part of the body, or loss of coordination are also signs of a serious neurological event.