Within the framework of a prospective double-blind and randomized study evaluating the efficacy of continuous intrathecal baclofen therapy (CIBT) on paroxysmal dysautonomia (main objective) and hypertonia, recovery and tolerance (secondary objectives) during the initial recovery phase of severe head injury, continuous intrathecal baclofen infusion will be delivered. The first week of study is double-blind: the first of two parallel groups receives CIBT and the second group receives placebo. The main outcome (number of neurovegetative episodes) is assessed at the end of first week. The second week of study is open labeled: active treatment is continued in the first group and the second group starts active CIBT treatment. The third week of study, treatment is stopped in both groups.