Andrew Peterson and Tim Baynepatients with traumatic etiologies are unlikely to transition to the MCS if they remain in a VS
longer than 12 months (Multi-Society Task Force 1994). In current clinical practice, the transi-
tion from the VS to the MCS is marked by the repeated and task-appropriate production of at
least one of the following behaviors: sustained visual pursuit, localization of noxious stimuli, and
command-following (Giacino et al. 2002). Patients who communicate (e.g., respond correctly
to a series of questions) or use objects appropriately (e.g., demonstrating how a coffee mug is
used) are taken to have left the MCS and to have entered a state of “full consciousness,” albeit
a state of consciousness that will typically be characterized by confusion and disorientation
(Giacino et al. 2014).
The VS and the MCS can be contrasted with the Locked-In-Syndrome (LIS), a disorder that
is caused by focal lesions to the brainstem resulting in widespread paralysis (Bauer et al. 1979).
LIS patients resemble post-comatose patients in possessing the capacity for only a very restricted
range of behaviors. However, unlike VS or MCS patients, LIS patients have not suffered damage
to the cortical structures responsible for awareness. Their capacity for motor responses is severely
limited, but they possess a normal suite of rational capacities and are undoubtedly conscious.
Discussion of post-comatose disorders of consciousness has centered on two sets of questions.
The first set of questions concerns the ascription of consciousness to these patients. The border
between unconsciousness and consciousness in post-comatose disorders has traditionally been
taken to coincide with the border between the VS and the MCS; indeed, the very labels for
these diagnoses presuppose that only MCS patients have a standing capacity for consciousness.
However, this assumption has been undermined over the last decade by neuroimaging and elec-
troencephalographic (EEG) data, which suggest that significant numbers of patients who appear
to be in the VS at the bedside—and indeed are VS according to current medical guidelines—do
retain some form of consciousness. Such patients can be described as “covertly conscious.”
The second set of questions concerns the implications of this research for our treatment of
post-comatose patients. Should neuroimaging and EEG measures be incorporated into the rou-
tine clinical assessment of such patients? If so, how should the information that is gleaned from
such tests impact on the medical care that is provided to them? And in what way should the
ascription of consciousness to these patients change our view of their moral status?
The remainder of this chapter examines the debates surrounding these two sets of questions:
Sections 3 through 6 examine the question of how covert consciousness might be investigated.
Section 7 examines the implications of covert consciousness for diagnostic taxonomy, while
Section 8 considers some of the ethical issues raised by the discovery of covert consciousness in
post-comatose patients.
3 Bedside Behavioral ExaminationThe question of whether post-comatose patients are conscious has traditionally been addressed
by bedside examination. The most widely used examination is the JFK-Coma Recovery Scale-
Revised (CRS-R), which tests the capacity of patients to execute a range of behaviors, such
as raising an arm in response to command or fixating on a visual stimulus. Individuals who
perform well on the CRS-R are regarded as being either minimally conscious or—if they
show evidence of the capacity to communicate and use objects in appropriate ways—as having
entered a state of full consciousness.
One’s attitude toward the CRS-R (and related behavioral examination schedules) will
depend on one’s view of the relationship between consciousness and behavior. Such sched-
ules carry the implicit assumption that the capacity to produce behaviors of the relevant type
is strongly correlated with the presence of consciousness, whereas the incapacity to produce