Visual pursuit in the severe disorder of consciousness

Visual pursuit is a key descriptor of the minimally conscious state (above 80% of cases). It is also observable in about 20% of subjects in vegetative state. Its reappearance after severe brain damage anticipates a favorable outcome, with recovery of consciousness in 73% of subjects (45% in the absence of it). We considered retrospectively 395 subjects in vegetative state because of traumatic (63%), massive acute vascular (30%), or diffuse anoxic-hypoxic (7%) brain damage consecutively admitted to one dedicated unit during the years 1998-2008. Visual tracking was observed in 290 subjects (73.4%) and was already detectable within 50 days from brain injury in about 60% of post-traumatic or vascular subjects and 21% of anoxic-hypoxic patients. After 230 days of follow-up or more, it was observed in 89% and 88% of post-traumatic and vascular subjects and in 67% of anoxic-hypoxic patients. Rating with the Glasgow Outcome Scale (GOS) was better in those subjects with recovered visual tracking and inversely correlated with the time of reappearance in post-traumatic and vascular subjects; also the subjects with late recovery of eye tracking (230 days or more) had better GOS outcome than those without it. The observation of visual tracking reappearing in subjects in vegetative state would reflect recuperation of the brainstem-cortical interaction and overall brain functional organization that are thought to sustain consciousness and are interfered with by the "functional disconnection," resulting in the vegetative state.