Pupillometric Variation in Traumatic versus Ischemic Brain Injury

Introduction: The pupillary light reflex (PLR) is used to determine neurologic status. The study of the PLR as a biomarker for distinguishing between subjects with different neurological diseases is not established. We studied PLR alterations in subjects with traumatic brain injury (TBI) and acute ischemic stroke (AIS).

Methods: PLR recordings were taken with both a smartphone pupillometer and a digital infrared pupillometer. AIS subjects presented with large vessel occlusion and were recruited prior to mechanical thrombectomy. TBI subjects (patients with subdural hematoma, intraparenchymal hemorrhage, and/or traumatic subarachnoid hemorrhage in a neurological intensive care unit) were recruited from hospitalized patients in a neurological intensive care unit. PLR parameter measurements were compared between healthy and AIS, AIS and TBI cohorts for both devices using a student’s t-test.

Results: Eight subjects with AIS, 84 subjects with TBI, and 132 healthy subjects were enrolled in this study. Subject demographics were: 63% female, mean age 64, 7 Caucasian, 1 Hispanic for AIS; 67% female, mean age 36, 84 Caucasian, 12 African American, 24 Asian, 8 Hispanic, 4 Native American for healthy; and 30% female, mean age 62, 63 Caucasian, 4 African American, 7 Asian, 6 Hispanic, 3 Native American, 1 Pacific Islander for TBI. In AIS patients, all occlusions were in the middle cerebral artery territory. TBI subjects had either acute subdural hematoma or contusion as the primary lesion. A significant (p < 0.05) difference was seen between healthy and AIS subjects for percent change and mean and maximum constriction velocity for both devices. AIS and TBI subject comparison found significant differences between minimum and maximum diameter and mean dilation velocity.

Conclusion : These results suggest that the effects of ischemic stroke on PLR parameters are different from those of TBI. Such differences could be useful in distinguishing types of neurological injury during pre-hospital triage.