Severe Brain Damage: Coma and Related Disorders of Consciousness

Progress in intensive care efforts has increased the number of patients who survive severe acute brain damage. Although the majority of these patients recover from coma within the first days after the insult, some permanently lose all brain function (i.e., brain death), while others evolve to an unresponsive wakefulness syndrome or a minimally conscious state. A nosological classification now clearly defines these different altered states of consciousness and their diagnostic clinical signs. The behavioral evaluation is the primary way to assess patients’ level of consciousness, even though sensorimotor impairments, aphasia, or fluctuations of vigilance levels can conceal the presence of consciousness. Functional neuroimaging and electrophysiology studies are changing our understanding of patients with coma and related states and more generally on the neural correlates of consciousness. These new tools are used to complement the clinical diagnosis and help assess patients more accurately. Some severely brain-damaged patients may thus show residual cortical processing in the absence of any behavioral signs of consciousness. Treatments are still scarce, but recent avenues include pharmacological interventions and noninvasive brain stimulation techniques. Ethical issues, end-of-life decision, pain, and quality of life are also some of the challenges clinicians face when working with this fragile population.