Fast and Slow Recovery of Consciousness Following Traumatic Brain Injury.

Background: Consciousness recovery after severe traumatic brain injury (sTBI) can take minutes to years. Despite this variability, we hypothesized that we could identify subgroups with distinct temporal recovery trajectories and that these subgroups would have distinct clinical features.

Methods: We conducted a retrospective cohort study to analyze recovery trajectories for patients with sTBI (Glasgow Coma Scale [GCS] score ≤ 8) admitted to Stony Brook University Hospital from 2010 to 2019. Patients meeting our criteria for recovery (GCS score ≥ 13) were classified into cohorts using the slopes of their recovery trajectories. We then characterized these groups by their clinical features, neuroimaging, and electroencephalography (EEG).

Results: A total of 501 patients with sTBI (348 men, mean age 51 years) were included in this study. Of these, 299 recovered. After analyzing their recovery rates, two distinct groups emerged, (1) fast recovery (n = 215) and (2) slow recovery (n = 84), with a median recovery time of 6 (interquartile range [IQR] 2-12) vs. 33 (IQR 27-44.75) days. Slow recovery patients had higher Injury Severity Scores (median 30 [IQR 25-41.75] vs. 24 [IQR 16-30]; 95% confidence interval [CI] 4.4495-10.6105; P < 0.001), more thalamic injury on neuroimaging (normalized volume [voxels] - 0.664 vs. 1.74; R² = 0.781; P < 0.016), and impaired interhemispheric connectivity on EEG (phase-locking value 0.35 vs. 0.44; 95% CI 0.055-0.14; P < 0.001).

Conclusions: Recovery after sTBI falls into two broad categories, distinguishable by injury severity, thalamic injury, and disrupted interhemispheric connectivity. This model accounts for heterogeneity in TBI outcomes and represents progress toward identifying targets for future neuromodulatory therapeutic development.