Neuropsychiatric Consequences of Subjective Return-to-Activity Measures

Pupillary light reflex (PLR) has shown potential as a diagnostic and near-term prognostic mild traumatic brain injury (mTBI) biomarker. An initial assessment of 146 West Point cadets who sustained an mTBI found that about half did not return to their baseline PLR values despite being cleared for unrestricted return to activity (uRTA). The present analysis investigates the possible immediate neuropsychiatric consequences of the failure to return to baseline PLR values.

The study included 146 cadets (agemean = 19.09 ± 1.25 years) at the United States Military Academy who sustained a concussion and successfully completed return-to-activity (RTA) progression. Assessments included PLR from both eyes (Neuroptics PLR 3000) and standard concussion testing as well as psychological (BSI-18) and neurocognitive (ImPACT) tests. Each cadet's PLR diameter change, maximum constriction velocity, and average dilation velocity at the unrestricted return to activity (uRTA) was compared to their baseline value. Psychological and neurocognitive differences at uRTA between cadets who did (i.e., returners) or did not (i.e., nonreturners) return to their baseline PLR values by uRTA were assessed via general/generalized linear models based on dependent variable structure.

Nonreturners demonstrated discrepancies in PLR measures and standard RTA criteria in that standard RTA criteria were met but PLR measures had not returned to baseline. Although there was some variation among the cohort, the majority of cadets who did not return to their baseline MCV had higher depression ( χ2[1] = 9.96, P = .002), anxiety ( χ2[1] = 5.49, P = .019), and somatization ( χ2[1] = 9.45, P = .002) symptom scores and took longer to return to activity ( χ2[1] = 6.22, P = .013). In contrast, cadets who did not return to their baseline average dilation velocity tended to return to activity faster ( χ2[1] = 10.49, P = .001). No significant cognitive differences were found between returners and nonreturners.

Results indicate that PLR nonreturners tended to have worse scores for some neuropsychological symptoms when cleared for full activity. Experiences of depression, anxiety, and somatization are not only unpleasant but may interfere with optimal functioning. Objective measures to understand risk profiles for returning service members to duty are vital to preserving far-forward combat power and providing commanders with much needed information to make tactical decisions.