Brain Function in the Vegetative State

Abstract

The vegetative state (VS) is a devastating medical condition characterized by preserved wakefulness contrasting with absent voluntary interaction with the environment (Figure 1). It can be diagnosed soon after a brain injury and can be partially or totally reversible, or it may progress to a persistent VS or death. It is important to distinguish between VS, persistent VS and permanent VS. Persistent VS is arbitrarily coined as a VS 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,¹ but does not imply irreversibility. Permanent VS implies the prediction that the patient will not recover. It was introduced by the American Multi-Society Task Force on PVS¹ in 1994 to denote irreversibility after three months following a non-traumatic brain injury and twelve months after traumatic injury. 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 VS.^2.The question which most concerns relatives and doctors caring for patients with vegetative state is whether a recovery is possible. The Task Force analyzed the prognosis of these patients and identified three factors that clearly influenced the chances of recovery: age, etiology, and time already spent in VS. The outcome is better after traumatic than non-traumatic brain injury, better in children, and worse as time passes. Clinical, electroencephalographic (EEG), evoked potentials (EP), or structural imaging data do not permit an accurate prognostication in VS.¹