Clinical and instrumental evaluation of chronic disorders of consciousness

With the increasing level of intensive care in modern time available, more people survive to brain injury, developing a chronic disorder of consciousness such as vegetative state (SV) and minimally conscious state (MCS). The most important difference between the two conditions is the presence or the absence of definite behavioral evidence of self or environmental awareness. Several studies have been performed to identify reliable tools to assess the presence of awareness and to allow differential diagnosis between VS and MCS. The most important clinical evaluation tool is represented by the Coma Recovery Scale-Revised (CRS-R) composed of six sub-scale addressing auditory, visual, motor, oromotor/verbal, communication and arousal processes. Since the bedside examination of consciousness in severely brain damaged patients is very challenging and often complicated by the presence of underlying deficits in the domain of verbal or non-verbal communication functions, paraclinical measures have been also identified. EEG standard, sleep EEG and EPs present characteristic features that distinguish VS from MCS. In the last period, fRMI studies have offered the possibility to measure directly and non-invasively severely brain damaged patients' brain activity and show that at least some patients, who appear unresponsive, may retain higher levels of self and environmental awareness than would otherwise be suggested on bedside examination.