Spontaneous blinking behaviour in persistent vegetative and minimally conscious states: Relationships with evolution and outcome

There is evidence that spontaneous blinking correlates with cognitive functions. This arises from the observation that blinking rate (BR) is modulated by arousal levels, basic cognitive processes (e.g., attention, information processing, memory, etc.) and more complex cognitive functions (e.g., reading, speaking, etc.). The aim of this work was to test the role of BR evaluation in the assessment of cognitive network functioning in awake patients with consciousness deficits. Thirteen patients were recruited for the study, and were assessed by the Glasgow coma scale (GCS) and Glasgow outcome scale (GOS) on admittance and discharge, respectively. A level of cognitive functioning scale (LCFS) score was assigned at every change in awareness or at least every 2 weeks. At the same time as the clinical tests, the BR was observed for a 5-min period. Ten healthy subjects, observed throughout three non-consecutive days, formed the control group. The BR underwent a different temporal behaviour in the two diagnostic categories. In the persistent vegetative state (PVS) group it remained stable throughout time and linked with the clinical conditions of the patients; whereas in the non-persistent vegetative state (NPVS) group it decreased over time as the cognitive conditions improved. Moreover, a strong inverse correlation was found between overall BR values and LCFS scores. We have concluded that the blinking behaviour changes manifested in PVS and NPVS patients reflect different evolution phases of a cholinergic–dopaminergic imbalance, and that a reduced BR characterizes the early stages of consciousness recovery.