Strength of Recommendations: Weak.
Quality of Evidence: Low, from Class III studies and indirect evidence.

Adult and Pediatrics

1. Pupils should be assessed in the field for use in diagnosis, treatment, and prognosis.
2. When assessing pupils:
   • Evidence of orbital trauma should be noted.
   • Pupils should be measured after the patient has been resuscitated and stabilized.
   • Left and right pupillary findings should be identified
     • Unilateral or bilateral dilated pupil(s).
     • Fixed and dilated pupil(s).

Asymmetry is defined as > 1mm difference in diameter. A fixed pupil is defined as < 1mm response to bright light

The pupillary exam is an essential component of the post-traumatic neurological exam. It consists of assessment of the size, symmetry and reaction to light of both pupils. The light reflex depends on a properly functioning lens, retina, optic nerve, brain stem, and oculomotor nerve (cranial nerve III). The direct pupil response assesses unilateral function of the III nerve; the consensual response assesses the function of the contralateral III nerve. Absence or asymmetry of these reflexes may indicate a herniation syndrome or ischemia of the brain stem.

Pupillary asymmetry less than 1 mm is normal and has no pathologic significance.10 In one study of 310 healthy volunteers with 2,432 paired measurements using advanced technology, asymmetry of pupillary size greater than 0.5 mm was seen in less than 1% of patients and was rarely seen in TBI patients unless the ICP exceeded 20 mm Hg.17

Increased intracranial pressure resulting in uncal herniation compresses cranial nerve III, resulting in a reduction of parasympathetic tone to the pupillary constrictor fibers, producing a dilated pupil with decreased reactivity. Destruction of the nerve also results in a dilated and fixed pupil. Bilaterally dilated and fixed pupils are consistent with direct brain stem injury, as well as with marked elevation of ICP. Metabolic or cardiovascular disturbances including hypoxemia, hypotension, and hypothermia are associated with dilated pupils and abnormal reactivity, making it necessary to resuscitate and stabilize the patient before assessing pupillary function.11,13

Direct trauma to cranial nerve III in the absence of significant intracranial injury or herniation may result in pupillary abnormalities usually associated with ocular motor deficits. Asymmetric pupillary constriction can make the contralateral pupil appear dilated. Following trauma, as the result of a carotid dissection, sympathetic chain function may be impaired, resulting in Horner's syndrome.4 These patients also have ptosis associated with the miotic eye, with the contralateral "dilated" pupil having a normal brisk constriction to light. This assessment may be difficult in the field.

Pupillary function may be an indicator of brain injury after trauma, but it is neither a specific indicator of injury severity or involved anatomy. Nevertheless, studies support the assessment of pupillary functions in the acute setting of trauma as both a guide to immediate medical decision making, and as a long term prognosticator.2,6,9,16,7

For this update Medline was searched from 1996 through July 2006 using the search strategy for this question (see Appendix B), and results were supplemented with literature recommended by peers or identified from reference lists. For adult studies, of 24 potentially relevant publications, 5 were used as evidence for this topic. For pediatric studies, of 9 potentially relevant publications 4 were used as evidence for this topic. (Note: In the previous edition of these guidelines, there were no evidence tables for this topic.)

1. Pupils should be assessed in the field for use in diagnosis, treatment, and prognosis.
2. When assessing pupils:
   • Evidence of orbital trauma should be noted.
   • Pupils should be measured after the patient has been resuscitated and stabilized.
   • Left and right pupillary findings should be identified
     • Unilateral or bilateral dilated pupil(s).
     • Fixed and dilated pupil(s).

Asymmetry is defined as > 1mm difference in diameter. A fixed pupil is defined as < 1mm response to bright light

Adult

Foundation. The relationship of pupillary findings in the field to outcome has not been studied. Though there are no prehospital data, studies frominhospital settings support a relationship between pupillary findings and outcome.1,12,14 There is a strong correlation between fixed, dilated pupils and ultimate mortality.6,9,16 Also, inhospital studies suggest that the pupillary findings have prognostic value, especially when combined with other physical findings.1,12,14,15

Chesnut et al. retrospectively analyzed data from 608 patients with severe TBI to assess the reliability of pupillary asymmetry in predicting the presence and location of intracranial mass lesions.3 Pupillary asymmetry had a positive predictive value of 30% with almost 80% of those patients having a contralateral lesion to the pupil finding. Anisocoria had a sensitivity of 40% and a specificity of 67%; even when the pupils were different by more than 3 mm there was a 43% positive predictive value. Thus, a single measurement of pupillary asymmetry is neither a sensitive nor specific finding in either identifying or localizing an intracranial mass lesion.

Mamelak et al. studied 672 TBI patients aged 0 - 80+ years. They found that age was the most important predictor of outcome, followed by initial motor exam and then by pupil response, demonstrating some correlation between pupillary response and outcome.7

Pediatrics

Foundation. There are few studies that specifically address the pupillary assessment in children following TBI. A prospective study of 98 pediatric patients found that 33% of those with aCT scan abnormality had a normal neurologic exam.5 In a prospective study of 265 pediatric patients the clinical predictors of intracranial injury were evaluated. Headache, pupillary response and initial GCS all indicated intracranial injury. However, a detailed clinical exam had no diagnostic value in detecting lesions found on head CT, supporting the poor sensitivity of pupil findings found in the first study.2

Massagli et al. studied 33 pediatric TBI patients and found that severity score and initial pupillary response were significantly related to long term outcome after 5-7 years, measured by the GOS (Glasgow Outcome Scale).8 McCabe et al. evaluated 30 pediatric patients diagnosed with "shaken baby syndrome" and found a 100% mortality for the 8 with bilateral fixed pupils on arrival.9

The prehospital and inhospital environments are significantly different. In the field pupillary exam is difficult to perform and is less reliable than when performed in the hospital. Given that prehospital providers are increasingly involved in decision making regarding therapeutic interventions and transport destinations, it is important to further investigate methods of enhancing accuracy of assessment measures such as pupillary examination. The following key questions need to be addressed:

1. Can prehospital providers accurately assess pupil size and light reactivity in the prehospital environment?
2. Are there ways to improve reliability of the pupillary exam in the field?
3. Is there acceptable interobserver reliability in the prehospital pupil examination?
4. Are pupil findings in the field predictive of patient outcome in both adult and pediatric TBI patients?
5. Does the common practice of performing serial pupillary examinations improve prognostic capability? The frequency at which examinations are performed needs to be determined.