Coma and Disorders of Consciousness
Key Clinical Questions
Which historical features and examination findings are useful in the diagnosis of patients with an acutely altered level of consciousness?
How is acute coma in hospitalized patients managed?
How does vegetative state differ clinically from the minimally conscious state?
What prognostic information should be given to surrogate decision makers for patients with severe alterations of consciousness?
Hospitalists are often required to assess patients with an abnormal level of consciousness, the most profoundly abnormal of which is coma. Coma is a state of unarousable unresponsiveness that may be produced by a number of acute or subacute central nervous system insults. The acute onset of coma is a medical emergency and requires urgent assessment, intervention, investigation, and specific therapy. Coma is distinct from vegetative state, minimally conscious state, and locked-in syndrome, conditions that are sometimes confused with it. The timing and probability of recovery from coma and the vegetative state and minimally conscious state differ considerably, depending on the nature of the underlying brain injury. This chapter will review the diagnosis and prognosis in disorders of consciousness, address ethical challenges arising in the care of these patients, and provide a guide to discussions with surrogate decision makers for the comatose or severely brain-injured patient.
COMA AND RELATED DISORDERS OF CONSCIOUSNESS
LETHARGY, OBTUNDATION, AND STUPOR
The terms lethargy, obtundation, and stupor have traditionally been used to denote mild, moderate, and severe disturbances in responsiveness respectively, but these terms pose a number of problems. Instead of specific states of brain function, these terms describe points on a spectrum of an abnormal level of consciousness. They are also poorly quantifiable and largely unvalidated in terms of their reliability, in contrast to other rating scales that may more reliably convey information about a patient’s condition. Based on this, it is advisable to avoid these terms, as they may cause confusion and imply a precision that is unwarranted.
Coma is a pathological brain state, referring to patients who are completely unresponsive and cannot be aroused to demonstrate increased alertness or purposeful movements. It is distinguished from syncope, concussion, and other forms of transient unconsciousness by its time course of more than 1 hour. Although some comatose patients recover rapidly, especially when coma is due to a concurrent systemic illness, a more gradual recovery is often seen for patients with brain injuries sufficient to produce even a day of coma. In such patients, recovery will be marked by the patient’s entering into a vegetative state or minimally conscious state, as defined below.
In its most basic neuroanatomical sense, coma requires disruption of either bilateral hemispheric functioning or the brainstem reticular activating system (Figure 207-1). Any process causing coma must disrupt either (or both) of these functional systems. Such causes include metabolic ...