What is the significance of assessing pupillary reflex in Traumatic Brain Injury (TBI)?

From the Guidelines

Assessing pupillary reflex is a crucial component of traumatic brain injury (TBI) evaluation, as it provides vital information about brainstem function and potential intracranial pressure changes, and should be performed serially to monitor for changes over time. When examining a TBI patient, clinicians should check pupil size, symmetry, and reactivity to light, noting any abnormalities such as fixed, dilated pupils (particularly unilateral) which may indicate increased intracranial pressure and compression of the third cranial nerve 1. This is in line with the recommendation to assess the severity of TBI using the Glasgow coma scale, specifically the motor response, as well as pupillary size and reactivity 1.

The significance of assessing pupillary reflex in TBI can be highlighted by the following key points:

• Pupillary abnormalities, especially unilateral dilation with decreased reactivity (anisocoria), can signal life-threatening conditions requiring immediate neurosurgical intervention, such as an expanding hematoma causing brainstem compression.
• The pupillary light reflex is particularly valuable because it remains relatively resistant to confounding factors like medications or metabolic disturbances that affect other neurological assessments.
• Regular pupillary assessment is essential in the early management of TBI and should be documented using standardized methods, ideally with pupillometers when available, to detect subtle changes that might indicate deterioration requiring prompt intervention.
• The initial clinical evaluation of severe TBI, including pupillary size and reactivity, has been validated as a key issue of the neurological outcome at 6 months, even in recent studies 1.

In clinical practice, the assessment of pupillary reflex should be performed in conjunction with other neurological assessments, such as the Glasgow coma scale, to provide a comprehensive evaluation of the patient's condition. The frequency of pupillary assessment may vary depending on the patient's condition, but it should be performed regularly, ideally every hour, to monitor for changes over time 1.

From the Research

Significance of Assessing Pupillary Reflex in TBI

• Assessing pupillary reflex is a crucial aspect of traumatic brain injury (TBI) management, as it can provide valuable information about the patient's neurological status 2, 3.
• The pupillary light reflex (PLR) is a key component of the neurological examination, and its assessment can be standardized and objectified using quantitative pupillometry (QP) 4.
• Studies have shown that an abnormal Neurological Pupil index (NPi) is associated with increased intracranial pressure (ICP) and neuroworsening in TBI patients 2, 5, 4.
• The sensitivity and specificity of abnormal NPi in predicting neuroworsening have been reported to be 51.43% and 91.67%, respectively, indicating that NPi may be an early indicator of neurological changes within 24 hours of ED admission in patients with TBI 4.

Relationship between Pupillary Reflex and Intracranial Pressure

• Research has shown a weak but statistically insignificant relationship between NPi and ICP, where reduced pupil reactivity may indicate a raised ICP 2.
• The strength of this trend appears to diminish post-decompressive surgery, suggesting that pupillometry may not be a reliable surrogate marker for ICP 2.
• However, NPi may still prove to be a useful tool in a multimodal prognostic assessment of the patient with acute brain injury 2.

Clinical Applications of Pupillary Reflex Assessment

• Automated infrared pupillometry (AIP) has shown promising results in predicting neural damage in TBI patients and may be useful in triaging comatose patients after blunt TBI 5.
• AIP could be used to identify patients who require intervention, such as craniectomy or ICP monitor placement, and those who do not require intervention 5.
• The assessment of pupillary reflex can also be used to evaluate the effectiveness of treatments, such as mannitol and hypertonic saline, in reducing ICP and improving outcomes in TBI patients 6.