Blink reflex as a prognostic indicator for patients with prolonged disorders of consciousness: a prospective case-control study.

Objective: This study aimed to investigate the characteristics of the blink reflex and its prognostic value for consciousness improvement in patients with prolonged disorders of consciousness (DOC).

Design: Prospective case-control study.

Setting: This study was conducted in a local hospital between March 2022 and March 2023.

Participants: Patients in a vegetative state/unresponsive wakefulness syndrome or in a minimally conscious state were enrolled within 3 months from their brain injury.

Primary And Secondary Outcome Measures: The early component (R1), ipsilateral late component (iR2) and contralateral late component (cR2) responses at baseline were recorded using electromyography. The patients' clinical diagnosis and the best Coma Recovery Scale-Revised (CRS-R) total score were assessed based on Chinese CRS-R evaluations.

Outcome Definition: At the 6-month follow-up, patients were categorised as improved or non-improved based on CRS-R score changes (improved (transition to a higher consciousness state); non-improved (worsened condition, static or death)).

Results: A total of 58 DOC patients were included in this study. Of the 58 DOC patients, 32 were classified as the improved group and 26 as the non-improved group. In the improved group, R2 responses were elicited in 30 patients, while only 16 patients in the non-improved group had elicited R2 responses. The non-improved group exhibited significantly lower R2 mean amplitudes (iR2 (105.08 µV vs 173.25 µV, p=0.01); cR2 (55.15 µV vs 114.03 µV, p=0.01)) and longer mean latencies (iR2 (41.08±6.72 ms vs 37.77±3.94 ms, p=0.03); cR2 (41.32±6.28 ms vs 37.48±4.07 ms, p=0.01)) compared with the improved group. The result demonstrated that the iR2 mean amplitude (OR=1.01, area under the curve (AUC)=0.78 (95% CI 0.63 to 0.93), sensitivity=78.12%, specificity=83.33%, p=0.02) and cR2 mean amplitude (OR=1.02, AUC=0.76 (95% CI 0.62 to 0.90), sensitivity=81.25%, specificity=72.22%, p=0.02) were significant predictors of consciousness improvement. Meanwhile, Pearson correlation analysis revealed that iR2 mean amplitude (r=0.42, p=0.003) and cR2 mean amplitude (r=0.53, p=0.001) significantly correlated with CRS-R score at baseline.

Conclusion: The R2 amplitude in patients with prolonged DOC may serve as a prognostic indicator for consciousness improvement.