The pupillary response is the involuntary constriction or dilation of the pupil in response to various stimuli. It is a critical component of the neurological examination and can be used to assess brainstem, spinal cord, and cortical function and localize lesions within these structures.
The pupillary response is also vital in diagnosing traumatic brain injury (TBI) and other forms of head trauma. The pupil is a highly vascular organ; therefore, its size can be used as an indirect measure of intracranial pressure (ICP).
This post discusses the pupillary light reflex in TBI and how doctors can use it to aid diagnosis. The pupillary response is a valuable prognostic indicator of injury severity, recovery potential, and mortality risk.
What Happens During a TBI?
Head trauma can lead to several injuries, including contusions (bruises), lacerations, hematomas (blood clots), and fractures. The seriousness of the damage depends on several factors, including the force with which the person sustained it and the location of the impact.
In general terms, TBI is classified into three categories: mild traumatic brain injury (mTBI) refers to a loss of consciousness lasting less than 30 minutes; severe TBI is associated with loss of consciousness for over 30 minutes, and moderate TBI is characterized by a loss of consciousness lasting between 30 minutes and 24 hours.
Besides the severity of the injury, other factors that contribute to its effects include age, gender, and pre-existing conditions.
What Does Pupillary Response Show About the Severity of a TBI?
Traumatic brain injury can cause a variety of symptoms. One of the most common is a change in pupillary response, or how a patient’s eyes react to light.
When light hits the retina, it causes nerve cells to send signals to the brain; these signals travel through the optic nerve and down another set of neurons to reach the hypothalamus.
From here, hormones that tell the adrenal gland how much cortisol (aka epinephrine) it should release into the patient’s bloodstream are released.
But in traumatic brain injury, the signals can get cross and cause the hypothalamus to think there’s a threat in the environment when there isn’t one.
So, patients with TBI often have trouble falling asleep; they’re being kept awake by cortisol-related hormones released into their bloodstreams by their bodies as a response to perceived danger.
Eye exams may reveal more about a patient’s head injury than an MRI scan.
MRI scans have long been the gold standard for diagnosing traumatic brain injury, but recent research has shown that the evaluation of pupillary reaction may provide just as much information about a patient’s condition.
Recent studies have found that health experts can use specific eye movements to predict whether a person has suffered a concussion or other traumatic brain injury (TBI). The test measures how quickly patients can shift their gaze between two different points; faster times indicate more severe damage.
There are several eye parameters medical professionals can check for and use in their diagnosis, including:
- Eye tracking: This test measures how well patients can follow an object with their eyes. It’s beneficial for assessing whether someone has suffered from brain damage.
- Visual acuity: Visual acuity refers to the sharpness of one’s vision—the ability to see clearly. Visual acuity testing can help determine whether a person has suffered from brain damage and the severity of their condition.
- Visual fields: This refers to the areas of the patient’s vision that are visible without moving their eyes. If a person has suffered from brain damage, they may have limited visual fields—meaning they can only see things in specific areas of their field of vision.
The pupillary response is a good determinant of Traumatic Brain Injury
Doctors can detect many indicators of brain damage during a person’s initial examination. The pupillary response is one of these indicators. If a patient has suffered from brain damage, their pupils will not normally react to light or other stimuli.
For example, if they are in a dark room and someone turns on the lights, their pupils should constrict (become smaller). With brain injury, however, this doesn’t happen.
The reason is that the brain is damage and cannot send out the signals to cause this response. In addition, if a patient’s pupils do not dilate (become larger) when they are in bright light, this can also indicate that they have experienced brain damage.
Although there are many indicators of Traumatic Brain Injury or TBI, pupil response is one of the most common ways doctors can determine whether a person has suffered from brain damage.
Doctors should use the pupillary response in combination with other tests
Although the pupillary test is a beneficial indicator of brain damage, it is not conclusive. For example, some patients with TBI may be able to dilate their pupils normally but do not have the cognitive function necessary to perform other tests. In these cases, doctors will also look at brain scans and other indicators of Traumatic Brain Injury or TBI.
Doctors must combine the pupillary response with other diagnostic tests to determine whether a person has suffered from brain damage.
Other tests doctors can employ alongside evaluating their pupillary response include the Glasgow Coma Scale (GCS) Test, a three-part evaluation of the brain that doctors can use to measure the severity of a patient’s TBI and determine if they are likely to suffer from long-term effects.
Injury and Determine
They can use an electroencephalogram (EEG), which measures electrical activity in the brain by placing electrodes on the head and recording brain waves.
Doctors may also use an MRI scan which works by taking a series of detailed images of the brain and surrounding tissue. This can help doctors detect any areas of damage or injury and determine if there is any bleeding or swelling in the brain.
The CT scan is a type of medical imaging that uses a series of x-rays to create cross-sectional images of the body. Doctors can use these images to see how much damage has been done to the brain and if there is any bleeding or swelling.
It’s essential to have trained medical professionals evaluate the pupillary response of patients.
There are several risks associate with wrongly performing pupil evaluations. That is why it’s crucial to have trained medical professionals evaluate the pupillary response of patients. The dangers of incorrectly assessing pupil size include misdiagnosis, mistreatment, or over-treatment of an injury or even death.
These risks are severe and can have a lasting impact on the patient’s health. The good news is that medical professionals can accurately assess pupil size and react appropriately to any changes with proper training.
The pupilometer and its effectiveness in treating traumatic brain injuries
Given the risks we mentioned, it’s essential to have a device that can accurately assess the size of your patient’s pupils. The pupilometer is a tool use by medical professionals to measure the size of a person’s pupil and determine if there is any trauma to the brain.
Pupilometer works by utilizing a light source to illuminate the eye. The pupilometer then uses a lens to create an image of the patient’s pupils on a screen for easy viewing by medical professionals. This is an effective way of assessing trauma in patients with traumatic brain injuries because it can be use anytime and does not require assistance from other people.