Questions remaining about the minimally conscious state

Disorders of human consciousness continue to fascinate and perplex neurologists and neuroscientists. In their landmark monograph, Plum and Posner1 drafted the first comprehensive map of this elusive area and provided the now widely accepted clinical definitions of consciousness and its states of impairment including stupor and coma.

Within the continuum of brain damage resulting from diffuse neuronal insults by trauma, hypoxia, or ischemia, several distinct clinical syndromes have been identified and accepted by neurologists. At the most extreme end, the syndrome of brain death indicates the permanent and global loss of neuronal function such that all the clinical functions of the brain are lost permanently.2 The persistent vegetative state (PVS), a condition whose name and essential features were described in 1972 by Plum and Jennett3 and further delineated in a 1994 multi-society task force report,4,5⇓ features the tragic and ironic dissociation of the two cardinal elements of human consciousness: wakefulness and awareness. Wakefulness is maintained but awareness is lost because the lesions producing PVS preserve the ascending reticular activating system but disconnect it from the thalami and cerebral hemispheres.6

Neurologic disorders that impair consciousness have important ethical, legal, political, and economic implications, largely because of the poignancy of affected patients’ loss of our uniquely human faculty and the vexing questions that follow of why, when, and how we should treat such patients. Brain death is …