The Minimally Conscious State: Neuroimaging and Regeneration*

The minimally conscious state (MCS) is a clinical manifestation of severe brain injury. While there are no evidence-based criteria, diagnostic guidelines were reached in a series of consensus development workshops [1]. The differential diagnosis of the minimally conscious state is important and includes the vegetative state (transient, persistent and permanent), coma and the locked-in syndrome (Table 1). Although sometimes confused in the lay media, none of these states indicate brain death. In recent years, neuroimaging studies have shed light on the underlying pathogenesis of both minimally conscious state and vegetative state and providing insights into the basis of the neural network subserving consciousness. These investigations are likely to have an increasing diagnostic role in severe brain injury. Like the vegetative state, the minimally conscious state may be a longterm disorder of consciousness, but it may also represent a transition phase between coma, followed by the vegetative state and eventually normal consciousness. Animal studies and more recent human research have indicated, contrary to earlier understanding, that late restoration of functioning can occur due to underling axonal repair. These imaging studies, utilising positron emission tomography (PET scanning) and functional MRI (fMRI) have shed new light on this potential for neural recovery. These techniques may potentially provide a substrate for experimental interventional therapies, such as drugs and neurotrophic factors. Furthermore, a recent study has challenged the clinical criteria for the persistent vegetative state and underlined the importance of neuroimaging in assessment of disorders of consciousness [2].