Pupil Abnormality Frequency in the First 72 Hours Improves IMPACT score in Traumatic Brain Injury

In patients with traumatic brain injury (TBI), baseline pupillary assessment is common. However, the incidence and frequency of pupil abnormalities within the first several days remain poorly characterized.

Our aim was to test the association between pupil abnormality frequency over the first 72 hours of admission and clinical outcomes.

We conducted a retrospective observational study of patients with a primary diagnosis of TBI with at least three quantitative pupillometry measurements within 72 hours at a single-center ICU from 2018 to 2022.

Neurological Pupil index (NPi), a quantitative composite metric for pupil reactivity, was obtained at each clinical neurologic assessment over 72 hours. Pupil measurements were defined as abnormal if they had a NPi of <3 in either eye, NPi asymmetry ≥0.7, or pupil size asymmetry ≥1mm. We tested the association of increased frequency of pupil abnormalities over 72 hours and unfavorable discharge disposition (death, hospice, or long-term care) using multivariable logistic regression, adjusting for confounders. We then compared whether the IMPACT model was improved by the frequency of pupil abnormalities using goodness-of-fit.

Of 131 patients, median age was 59 years, and 30% were women. Thirty-five percent had unfavorable discharge disposition. Pupil abnormalities occurred in 62%, 61%, and 88% of mild, moderate, and severe TBI patients, respectively. Odds ratio of unfavorable discharge for every 1% increase in pupil abnormality frequency was 1.03 (95% Cl, 1.01-1.05), equivalent to one additional abnormal pupil measurement within a 72-hour period. The adjusted IMPACT TBI model's goodness-of-fit improved with pupil abnormality frequency ( X ² =5.67, p =0.02).

Pupil abnormalities occur commonly in TBI and have the highest frequency in severe TBI. Increased pupil abnormality frequency is associated with unfavorable discharge disposition and improves performance of prognostic TBI models.

The goal of this study was to test the association between pupil abnormality frequency over the first 72 hours of admission and unfavorable discharge disposition and whether it improved the IMPACT model. In this retrospective observational study of 131 TBI patients at a single-center, we found that an increased frequency of pupil abnormalities across 72-hours significantly correlated with unfavorable discharge in patients and improved the IMPACT model's goodness-of-fit. These findings highlight the potential of long-term pupillary metrics and their role as not only a prognostic indicator in patients but also a tool that improves the performance of prognostic TBI models.