Spontaneous eye blink rate a good marker of consciousness after brain injury

In the postacute phase after brain injury, the spontaneous eye blink rate (EBR) is higher in patients in a minimally conscious state (MCS) and may help distinguish MCS from the vegetative state/unresponsive wakefulness syndrome (VS/UWS), a recent study has found.

Researchers enrolled 10 VS/UWS patients (mean age 50.3±17.8 years, 3 women) and 14 MCS patients (mean age 52.9±17.5 years, three women) who were admitted to a rehabilitation unit during the acute phase of their injury. EBR was recorded using online visual and offline electro-oculographic counts during two separate 3-minute rest conditions and while performing two auditory oddball tasks.

At rest, raw EBR was consistently higher in MCS patients than in VS/UWS comparators. This was true for both the first (17.99±3.39 vs 8.05±3.10 respectively; adjusted p=0.03) and second (25.80±3.97 vs 6.35±1.82; adjusted p<0.001) sessions. In the overall group and in either diagnostic subgroup, resting EBR did not change significantly from the first to the second session.

Similarly, EBR differed between two groups under cognitive load. Average EBR across both task sessions was significantly higher in the MCS vs VS/UWS groups (22.00±4.75 vs 3.70±1.46; adjusted p=0.04). As in the resting state, EBR showed no significant change between the two sessions in either diagnostic group.

“If our results will hold true in larger study populations, a simple and low-burden but decisive clinical marker, such as counting eye blinks over 3 min, will help to reduce rate of misdiagnosis in disorders of consciousness … without the need for additional high-tech methods,” the researchers said.