Cerebral Function in Vegetative State studied by Positron Emission Tomography

Abstract

After a period of coma, some patients enter a vegetative state (Fig. 1). Vegetative state is a clinical condition of ‘wakefulness without awareness’, first defined by Jennet and Plum in 1972 [1]. It can be diagnosed soon after a brain injury and can be partially or totally reversible or it may progress to a persistent vegetative state or death [2]. Table 1 summarizes the criteria for the diagnosis of vegetative state proposed by The American Neurological Association [2] and the American Academy of Neurology [3]. It is important to distinguish between vegetative state, persistent vegetative state, and permanent vegetative state. Persistent vegetative state is arbitrarily coined as a vegetative state present one month after acute traumatic or non-traumatic brain injury or lasting at least one month in patients with degenerative or metabolic disorders or developmental malformations [3] but does not imply irreversibility. Permanent vegetative state implies the prediction that the patient will not recover. It was introduced by the American Multi-Society Task Force on persistent vegetative state [3] in 1994 to denote irreversibility after three months following a non-traumatic brain injury and twelve months after traumatic injury (Fig. 1). However, even after these long and arbitrary delays, some patients may exceptionally recover. Hence, the American Congress of Rehabilitation Medicine advocates abandoning the term ‘permanent’ in favor of simply specifying the length of time patients have spent in a vegetative state [4]. The question which most concerns relatives and doctors caring for patients with vegetative state is whether a recovery is possible.