Restoring consciousness with vagus nerve stimulation

Patients lying in a vegetative state present severe impairments of consciousness [1Giacino J.T. Fins J.J. Laureys S. Schiff N.D. Disorders of consciousness after acquired brain injury: the state of the science.Nat. Rev. Neurol. 2014; 10: 99-114Crossref PubMed Scopus (452) Google Scholar] caused by lesions in the cortex, the brainstem, the thalamus and the white matter [2Adams J.H. Graham D.I. Jennett B. The neuropathology of the vegetative state after an acute brain insult.Brain. 2000; 123: 1327-1338Crossref PubMed Scopus (319) Google Scholar]. There is agreement that this condition may involve disconnections in long-range cortico–cortical and thalamo-cortical pathways [3Laureys S. The neural correlate of (un)awareness: lessons from the vegetative state.Trends Cogn. Sci. 2005; 9: 556-559Abstract Full Text Full Text PDF PubMed Scopus (503) Google Scholar]. Hence, in the vegetative state cortical activity is ‘deafferented’ from subcortical modulation and/or principally disrupted between fronto-parietal regions. Some patients in a vegetative state recover while others persistently remain in such a state. The neural signature of spontaneous recovery is linked to increased thalamo-cortical activity and improved fronto-parietal functional connectivity [3Laureys S. The neural correlate of (un)awareness: lessons from the vegetative state.Trends Cogn. Sci. 2005; 9: 556-559Abstract Full Text Full Text PDF PubMed Scopus (503) Google Scholar]. The likelihood of consciousness recovery depends on the extent of brain damage and patients’ etiology, but after one year of unresponsive behavior, chances become low [1Giacino J.T. Fins J.J. Laureys S. Schiff N.D. Disorders of consciousness after acquired brain injury: the state of the science.Nat. Rev. Neurol. 2014; 10: 99-114Crossref PubMed Scopus (452) Google Scholar]. There is thus a need to explore novel ways of repairing lost consciousness. Here we report beneficial effects of vagus nerve stimulation on consciousness level of a single patient in a vegetative state, including improved behavioral responsiveness and enhanced brain connectivity patterns.