In this study, researchers will show to caregivers of patients how to use a tDCS device (this device was designed to be easy to use, with fixed parameters and only one button to press to run the stimulation). They will be asked to apply a stimulation every day, 5 days per week during for 4 weeks, in chronic patients in minimally conscious state (MCS).

2 sessions of 4 weeks of stimulations will be realized, one anodal and one sham in a randomized order. Before and after each session, behavioral improvement will be assessed with the Coma Recovery Scale Revised (CRS-R). A final assessment will be done 8 weeks after the end of the sessions to assess the long term effect of tDCS.

A single session of tDCS showed positive effects on patients in MCS (study published in Neurology, 2014). Nevertheless, the effects went down after 1 or 2 hours. In a second study (Protocol ID: 2009/201/B) we have found that 5 days of tDCS increase the lasting of the effects up to one week.

To know if tDCS could be use in clinical daily practice, a new study will evaluate the effects of 20 minutes of tDCS over the left prefrontal dorsolateral cortex for 4 weeks, 5 days per week, in chronic patients in MCS.

2 sessions of 4 weeks of stimulation (total=20 stimulations per session) will be performed, one session will be real (anodal stimulation) and one placebo (sham stimulation).

Firstly, the patient will be seen at the hospital for a behavioral assessment (CRS-R) with one of his/her caregiver. The investigator will explain to the caregiver how to perform the stimulation. In addition, he/she will receive a folder and a video. The caregiver will take an exam to be sure he/she performs the tDCS properly.

Before and after each stimulation session, behavioral improvement will be assessed with the CRS-R by a trained neuropsychologist, at the hospital. A final assessment will be done 8 weeks after the end of the session to assess the long term effect of tDCS.

The compliance will be recorded by the deice to be sure that the caregiver performs the stimulation every day as expected.

Researchers expect to see (a) an improvement of the CRS-R total score at the end of the anodal session and (b) this improvement persists for 8 weeks.

Inclusion Criteria:

• be in an minimally conscious state
• be chronic (more then 3 months post insult)
• stable condition

Exclusion Criteria:

• NMDA receptor inhibitor drugs
• modification of the treatment during the protocol
• illness or infection during the protocol
• pacemaker
• metallic cerebral implant
• prior neurological disorder
• tDCS or other non-invasive brain stimulation treatment less than 3months before the inclusion in the present study