Every neurologist will agree that traumatic brain injuries can be challenging to diagnose. Traumatic brain injuries can cause various symptoms, including loss of consciousness, confusion, dizziness and personality changes. Unfortunately, these symptoms are common in patients with other conditions, such as head injury, psychological issues and stroke.
With these often-confusing symptoms, it’s difficult to distinguish between the different conditions. This is where pupillary evaluation comes into play during a neuro exam. Neurologists use pupillary evaluation to determine whether a patient has suffered a traumatic brain injury or another condition.
This article will discuss how pupillary evaluation works and why it’s one of the most important neurological tools for diagnosing brain damage.
The Basis of the Pupillary Response in Traumatic Brain Injury
While every traumatic brain injury case is unique, neurologists can use a few common symptoms to help tell the difference between TBI and other conditions.
One of these symptoms is the pupillary response in traumatic brain injury, which refers to how the patient’s pupils react in different situations. In a healthy person, the pupil will dilate when exposed to light and constrict when looking at an object up close.
And since there is a link between the eyes and the brain, neurologists can use the pupillary response in traumatic brain injury to help determine whether there is damage to one or both sides of the brain.
What Pupillary Response Parameters Should You Check?
During every evaluation of pupillary reaction, physicians will look at several parameters, including:
- Direct Response: The direct response is the quickest and most reliable method of evaluating pupillary reaction. When a light is shined in one eye and then quickly moved to the other, the pupil will usually constrict in both eyes if there is no damage in either hemisphere of the brain.
- Consensual Response: The consensual response is a method of evaluating pupillary reaction that involves shining a light in one eye and then moving it to the other. If there is damage to only one hemisphere of the brain, there will be a delay in the pupils’ response. The consensual response takes longer than the direct response because it requires more neural processing time for both eyes to communicate.
- Neurological Pupil Index: The neurological pupil index (NPi) is a method of evaluating pupillary reaction by measuring the time it takes for both pupils to constrict after exposure to light. This test measures the integrity of the brainstem and its connections between the eyes, ears, and those areas of the brain that control eye movement.
- Pupil Size: Traumatic brain injury can affect the size of the pupils. The pupils may become enlarged because of increased pressure within the brain, which causes fluid to leak out through membranes in the spinal cord. This leaking fluid can cause an increase in intracranial pressure and make it more difficult for blood vessels to constrict, resulting in dilated or enlarged eyes.
Pupilometry and Traumatic Brain Injury Treatment
Since we’ve established that pupillary evaluation is an integral part of a complete neurological exam, it’s essential to know how this evaluation is done. Pupilometry measures the size and shape of a person’s pupils during various light levels or stimuli.
A specialized machine called a pupilometer measures the size of the pupil in millimeters. This measurement is then recorded, and the examiner can use it to assess the integrity of the optic nerve and other visual pathways.
This device detects changes in a person’s pupils when they look at different light levels. If a person has damage to their visual pathways, such as from head trauma, their pupils will not react appropriately to the test stimuli. This can help doctors determine whether there is any damage to that person’s vision or brain function.
Why Use the Pupilometer?
Although doctors can use several other tools to measure eye size, the pupilometer is a popular option because it is inexpensive and easy to use. A person sits in front of the device and looks into one end while a light source measures their pupils.
This allows doctors to make quick and accurate assessments of a patient’s brain health without resorting to more expensive methods that require advanced equipment.
The device is also non-invasive and portable, making it an excellent option for various settings. Doctors, nurses, and other medical professionals who need to assess their patient’s health quickly frequently use it.