OBJECTIVE Deep brain stimulation of the thalamus was introduced more than 40 years ago with the objective of improving the performance and attention of patients in a vegetative or minimally conscious state. Here, the authors report the results of the Cortical Activation by Thalamic Stimulation (CATS) study, a prospective multiinstitutional study on the effects of bilateral chronic stimulation of the anterior intralaminar thalamic nuclei and adjacent paralaminar regions in patients affected by a disorder of consciousness. METHODS The authors evaluated the clinical and radiological data of 29 patients in a vegetative state (unresponsive wakefulness syndrome) and 11 in a minimally conscious state that lasted for more than 6 months. Of these patients, 5 were selected for bilateral stereotactic implantation of deep brain stimulating electrodes into their thalamus. A definitive consensus for surgery was obtained for 3 of the selected patients. All 3 patients (2 in a vegetative state and 1 in a minimally conscious state) underwent implantation of bilateral thalamic electrodes and submitted to chronic stimulation for a minimum of 18 months and a maximum of 48 months. RESULTS In each case, there was an increase in desynchronization and the power spectrum of electroencephalograms, and improvement in the Coma Recovery Scale-Revised scores was found. Furthermore, the severity of limb spasticity and the number and severity of pathological movements were reduced. However, none of these patients returned to a fully conscious state. CONCLUSIONS Despite the limited number of patients studied, the authors confirmed that bilateral thalamic stimulation can improve the clinical status of patients affected by a disorder of consciousness, even though this stimulation did not induce persistent, clinically evident conscious behavior in the patients. Clinical trial registration no.: NCT01027572 ( ClinicalTrials.gov ).

Objective: To investigate functional connectivity between the default mode network (DMN) and other networks in disorders of consciousness. Methods:We analyzed MRI data from 11 patients in a vegetative state and 7 patients in a minimally conscious state along with age-and sex-matched healthy control subjects. MRI data analysis included nonlinear spatial normalization to compensate for disease-related anatomical distortions. We studied brain connectivity data from resting-state MRI temporal series, combining noninferential (independent component analysis) and inferential (seed-based general linear model) methods.Results: In DMN hypoconnectivity conditions, a patient's DMN functional connectivity shifts and paradoxically increases in limbic structures, including the orbitofrontal cortex, insula, hypothalamus, and the ventral tegmental area. Conclusions:Concurrently with DMN hypoconnectivity, we report limbic hyperconnectivity in patients in vegetative and minimally conscious states. This hyperconnectivity may reflect the persistent engagement of residual neural activity in self-reinforcing neural loops, which, in turn, could disrupt normal patterns of connectivity. Patients in a vegetative state (VS) (also called "unresponsive wakefulness syndrome" 1 ) exhibit apparent dissociation between wakefulness and awareness, the 2 cardinal elements of consciousness.2 Onset of a VS, in which awareness is negatively affected, typically follows a coma and can be chronic and may evolve into a minimally conscious state (MCS).3 The current literature assumes a "passive" model of unawareness in both the VS and MCS, which is associated with widespread cerebral connectivity loss.In severe brain injury and postcomatose states, the default mode network (DMN), a major frontoparietal connectivity network of the resting brain connecting anterior and posterior cingulate with parietal and hippocampal regions, shows a breakdown of connectivity depending on the level of consciousness.4 Similar findings were found in healthy controls during altered states of consciousness such as anesthesia and sleep. 5The DMN 6 has been proposed as a correlate of the baseline cognitive state of a subject, and its link to memory and executive functions in normal and pathologic conditions suggests profound implications for consciousness. 7To date, interplay between the DMN and other brain networks has not been well explored in disorders of consciousness. We hypothesized that neural connectivity measured by resting-state From the Department of Neuroradiology (C.D.P., A.P., P.V.),