Functional Neuroimaging of Disorders of Consciousness

Abstract

An accurate and reliable evaluation of the level and content of cognitive processing is of paramount importance for the appropriate management of severely brain-damaged patients with disorders of consciousness.1 Objective behavioral assessment of residual cognitive function can be extremely challenging in these patients, as motor responses may be minimal, inconsistent, and difficult to document, or may be undetectable because no cognitive output is possible. This difficulty leads to much confusion and a high-level of misdiagnoses in the vegetative state (VS), minimally conscious state, and locked-in syndrome.2,3 Recent advances in functional neuroimaging suggest a novel solution to this problem; so-called ‘‘activation’’ studies can be used to assess cognitive functions in altered states of consciousness without the need for any overt response on the part of the patient. In several recent studies, this approach has been used to detect residual cognitive function and even conscious awareness in patients who behaviorally meet the criteria defining the VS.4–6 Similarly, these techniques have been used in other studies to guide therapeutic interventions and track recovery processes.7,8 Such studies suggest that the future integration of emerging functional neuroimaging techniques with existing clinical and behavioral methods of assessment will be essential in reducing the current rate of misdiagnosis. Moreover, such