Bringing neuroimaging tools closer to diagnostic use in the severely injured brain

In a vanguard study reported in this issue of Brain , Coleman et al. (page 2494) used hierarchically organized passive language tasks and functional magnetic resonance imaging (fMRI) to study 14 patients with severe brain injuries. Functional levels of the study subjects ranged across a spectrum from vegetative state to minimally conscious state, and severe disability following emergence from the minimally conscious state. The investigators assessed three levels of speech processing beginning with comparisons of auditory stimuli to a silent baseline, followed by comparisons of intelligible speech versus unintelligible noise, and finally advancing to high-level semantic contrasts using English sentences containing words with either high or low ambiguity of interpretation. Notably, their findings revealed evidence of preserved higher level language processing among a subset of three patients meeting the criteria for vegetative state. Taken together with an earlier single-subject study of one of the vegetative state patients (Owen et al. , 2006), the results support further developing these and other neuroimaging tools to aid the difficult diagnostic assessments of patients with severe brain injuries (Laureys et al. , 2004; Schiff, 2006).Owen et al. (2006) earlier demonstrated at least minimally conscious state level function in one of the three vegetative state patients using another novel imaging technique that is operationally exchangeable with behavioural evidence of command following as judged clinically at the bedside. The patient demonstrated the ability to follow complex commands. Based on these earlier studies, it could be strongly argued that this vegetative state patient in fact reflects a novel category of ‘non-behavioural’ minimally conscious state (Fins and Schiff, 2006). This distinction may ultimately be of considerable importance as prospective studies …