Severe acquired brain injuries can be caused by traumatic brain injury, stroke or anoxia, among others and can lead to Disorders of Consciousness (DOC), an umbrella term that encompasses a wide range of different clinical conditions such as coma, the Unresponsive Wakefulness Syndrome (UWS) and the Minimally Conscious State (MCS). Coma usually lasts from a few days to few weeks and it is defined as a state of profound unawareness from which the patient cannot be aroused; eyes are closed, and a normal sleep-wake cycle is absent. The UWS denotes a condition of wakefulness without (clinical signs of) awareness; UWS patients may open their eyes but exhibit only reflex (i.e. non-intentional) behaviors and are therefore considered unaware of themselves and their surroundings. On the other hand, the MCS denotes a condition where discernible behavioral evidence of consciousness is retained. More recently, given the heterogeneity of the MCS category, patients showing higher level responses, including reproducible movements to commands, intelligible verbalization and intentional communication (i.e. MCS+), have been distinguished from those showing lower level non-reflex responses (e.g. visual pursuit, object recognition; i.e. MCS-). Once patients recovery the ability to communicate or to use objects they are considered emerged from the MCS (EMCS).

Currently, the gold standard for the behavioural assessment of DOC patients is the Coma Recovery Scale-Revised (CRS-R) and the diagnosis is made according to the presence of certain behaviours. However, because of daily fluctuations, a minimum of 5 CRS-R evaluations within a short time interval are recommended, allowing to reduce the risk of misdiagnose to the 40%.

If the CRS-R criteria for the diagnosis of coma and UWS are somehow clear, the MCS and EMCS entities are the focus of a growing body of research. Despite all, the diagnostic criteria for DOC patients are becoming clearer and clearer, but markers to predict prognosis and functional outcome need to be better studied. Knowing the natural history of patients with DOC may help to an adequate prognosis, that is important not only for the patient and the family but also for treatment planning and provision of therapies and discharge. In particular, if there are existing studies about the prognosis of UWS and MCS patients, studies comparing MCS- and MCS+ patients are lacking. State of the art about the prognosis in DOC patients highlight a better outcome for patients in a MCS compared to patients in UWS, but little is known about a possible different prognosis between MCS+ and MCS- patients. A recent study stresses the need for prospective studies investigating differences in long-term functional outcome between patients in a MCS+ and MCS-. So far, the only available longitudinal study including MCS- and MCS+ patients followed 39 chronic DOC patient for two years after brain injury and assessed them with the CRS-R every 3 months. The sample included 16 patients in a UWS, 15 patients in a MCS-, 7 in a MCS+ and 1 in a EMCS and the authors did not find differences in the prognosis between MCS- and MCS+ patients, probably due to limited sample size.

Therefore, the first aim of this study is to investigate and compare the clinical evolution of a sample of patients with the diagnosis of MCS+ versus MCS- according to the CRS-R total score. In particular, the investigators focus our attention on the likelihood of emergence from the MCS and on the evolution of functional independence after the emergence from the MCS. The investigators hypothesize that those patients presenting preferentially complex behavioural responses will have better clinical trajectories including an increasing likelihood to emerge form MCS and a better functional outcome once emerged from the MCS.