LAUSR

Patients in the vegetative state (VS) generally remain in the same clinical situation, though some may evolve toward a minimally conscious state (MCS). It is very important to differentiate these two conditions, since the associated clinical decisions may be very distinct and pose different ethical dilemmas. In the case of permanent VS, characterized by irreversible damage, limitation of life-sustaining treatment may be decided. In comparison, patients presenting MCS are unable to maintain functional communication, but are occasionally able to follow instructions, utter some words, visually follow moving objects or people, and show emotions such as smiling, laughing or even crying. Neurological exploration in such cases is extremely difficult, since the patient movements may be very small, inconsistent and easily exhausted--thus giving rise to erroneous diagnostic interpretations. It has been estimated that 40% of all cases of VS actually constitute MCS--a circumstance that reflects the need to complement clinical exploration with other diagnostic methods. Positron emission tomography--computed tomography (PET/CT) is an emerging neuroimaging technique that can differentiate between VS and MCS. Its availability is still limited, however, and interpretation of the findings is sometimes difficult. PET/CT with F-2-fluoro-2-deoxy-dglucose (F-FDG)--a radiolabeled glucose analog--can be used to study brain activity. F-FDG uptake is related to cell transport, and thus assesses regional cerebral carbohydrate metabolism, representing an in vivo measurement of neuronal integrity. In recent years, several studies have correlated specific metabolic patterns to different levels of consciousness. In this regard, patients presenting VS show