increased number of hours of sleep and may be
drowsy between sleep bouts.
Stupor, from the Latin ‘‘to be stunned,’’ is a
condition of deep sleep or similar behavioral
unresponsiveness from which the subject can
be aroused only with vigorous and continuous
stimulation. Even when maximally aroused, the
level of cognitive function may be impaired.
Such patients can be differentiated from those
with psychiatric impairment, such as catato-
nia or severe depression, because they can be
aroused by vigorous stimulation to respond to
simple stimuli.
Coma, from the Greek ‘‘deep sleep or
trance,’’ is a state of unresponsiveness in which
the patient lies with eyes closed and cannot be
aroused to respond appropriately to stimuli
even with vigorous stimulation. The patient may
grimace in response to painful stimuli and limbs
may demonstrate stereotyped withdrawal re-
sponses, but the patient does not make local-
izingresponsesordiscretedefensivemovements.
As coma deepens, the responsiveness of the
patient, even to painful stimuli, may diminish or
disappear. However, it is difficult to equate the
lack of motor responses to the depth of the coma,
as the neural structures that regulate motor re-
sponses differ from those that regulate con-
sciousness, and they may be differentially im-
paired by specific brain disorders.
The locked-in syndrome describes a state in
which the patient is de-efferented, resulting in
paralysis of all four limbs and the lower cranial
nerves. This condition has been recognized at
least as far back as the 19th century, but its dis-
tinctive name was applied in the first edition of
this monograph (1966), reflecting the implica-
tions of this condition for the diagnosis of coma
and for the specialized care such patients re-
quire. Although not unconscious, locked-in pa-
tients are unable to respond to most stimuli. A
high level of clinical suspicion is required on
the part of the examiner to distinguish a locked-
in patient from one who is comatose. The most
common cause is a lesion of the base and teg-
mentum of the midpons that interrupts des-
cending cortical control of motor functions.
Such patients usually retain control of vertical
eye movements and eyelid opening, which can
be used to verify their responsiveness. They
may be taught to respond to the examiner by
using eye blinks as a code. Rare patients with
subacute motor neuropathy, such as Guillain-
Barre´ syndrome, also may become completely
de-efferented, but there is a history of sub-
acute paralysis. In both instances, electro-
encephalographic (EEG) examination discloses
a reactive posterior alpha rhythm
10
(see EEG
section, page 82).
It is important to identify locked-in patients
so that they may be treated appropriately by
the medical and nursing staff. At the bedside,
discussion should be with the patient, not, as
with an unconscious individual, about the pa-
tient. Patients with large midpontine lesions of-
ten are awake most of the time, with greatly
diminished sleep on physiologic recordings.
11
They may suffer greatly if they are treated by
hospital staff as if they are nonresponsive.
As the above definitions imply, each of these
conditions includes a fairly wide range of be-
havioral responsiveness, and there may be some
overlap among them. Therefore, it is generally
best to describe a patient by indicating what
stimuli do or do not result in responses and the
kinds of responses that are seen, rather than
using less precise terms.
Subacute or Chronic Alterations
of Consciousness
Dementia defines an enduring and often pro-
gressive decline in mental processes owing to
an organic process not usually accompanied
by a reduction in arousal. Conventionally, the
term implies a diffuse or disseminated reduc-
tion in cognitive functions rather than the im-
pairment of a single psychologic activity such
as language. DSM-IV defines dementia as fol-
lows: ‘‘A. The development of multiple cogni-
tive defects manifested by both: (1) Memory
impairment (impaired ability to learn new in-
formation or to recall previously learned infor-
mation); (2) One (or more) of the following
cognitive disturbances: aphasia (language dis-
turbance), apraxia (impaired ability to carry out
motor activities despite intact motor function),
agnosia (failure to recognize or identify objects
despite intact sensory function), disturbance in
executive function (i.e., planning, organization,
sequencing, abstracting).’’
The reader will recognize this definition as
an arbitrary restriction. Usually, the term de-
mentia is applied to the effects of primary dis-
orders of the cerebral hemispheres, such as
degenerative conditions, traumatic injuries,
and neoplasms. Occasionally, dementia can be
Pathophysiology of Signs and Symptoms of Coma
7
at least partially reversible, such as when it ac-
companies thyroid or vitamin B
12
deficiency
or results from a reversible communicating hy-
drocephalus; more often, however, the term
applies to chronic conditions carrying limited
hopes for improvement.
Patients with dementia are usually awake
and alert, but as the dementia worsens, may
become less responsive and eventually evolve
into a vegetative state (see below). Patients with
dementia are at significantly increased risk of
developing delirium when they become medi-
cally ill or develop comorbid brain disease.
Hypersomnia refers to a state characterized
by excessive but normal-appearing sleep from
which the subject readily, even if briefly, awak-
ens when stimulated. Many patients with either
acute or chronic alterations of consciousness
sleep excessively. However, when awakened,
consciousness is clearly clouded. In the truly
hypersomniac patient, sleep appears normal
and cognitive functions are normal when pa-
tients are awakened. Hypersomnia results from
hypothalamic dysfunction, as indicated later in
this chapter.
12
Abulia (from the Greek for ‘‘lack of will’’) is
an apathetic state in which the patient responds
slowly if at all to verbal stimuli and generally
does not initiate conversation or activity. When
sufficiently stimulated, however, cognitive func-
tions may be normal. Unlike hypersomnia, the
patient usually appears fully awake. Abulia is
usually associated with bilateral frontal lobe dis-
ease and, when severe, may evolve into akinetic
mutism.
Akinetic mutism describes a condition of
silent, alert-appearing immobility that charac-
terizes certain subacute or chronic states of
altered consciousness in which sleep-wake cy-
cles have returned, but externally obtainable
evidence for mental activity remains almost en-
tirely absent and spontaneous motor activity is
lacking. Such patients generally have lesions
including the hypothalamus and adjacent basal
forebrain.
The minimally conscious state (MCS) is a con-
cept that was recently developed by the Aspen
Workgroup, a consortium of neurologists, neu-
rosurgeons, neuropsychologists, and rehabilita-
tion specialists.
13
MCS identifies a condition of
severely impaired consciousness in which mini-
mal but definite behavioral evidence of self
(this can only be assessed verbally, of course)
or environmental awareness is demonstrated.
Like the vegetative state, MCS often exists as
a transitional state arising during recovery from
coma or worsening of progressive neurologic
disease. In some patients, however, it may be
an essentially permanent condition. For a de-
tailed discussion of the clinical criteria for the
diagnosis of the minimally conscious state, see
Chapter 9.
The vegetative state (VS) denotes the recov-
ery of crude cycling of arousal states heralded
by the appearance of ‘‘eyes-open’’ periods in
an unresponsive patient. Very few surviving pa-
tients with severe forebrain damage remain in
eyes-closed coma for more than 10 to 30 days.
In most patients, vegetative behavior usually
replaces coma by that time. Patients in the veg-
etative state, like comatose patients, show no evi-
dence of awareness of self or their environment.
Unlike brain death, in which the cerebral hemi-
spheres and the brainstem both undergo over-
whelming functional impairment, patients in
vegetative states retain brainstem regulation of
cardiopulmonary function and visceral autono-
mic regulation. Although the original term per-
sistent vegetative state (PVS) was not associated
with a specific time, the use of PVS is now com-
monly reserved for patients remaining in a veg-
etative state for at least 30 days. The American
Neurological Association advises that PVS be
applied only to patients in the state for 1 month.
Some patients recover from PVS (see Chapter
9). Other terms in the literature designating the
vegetative state include coma vigil and the apa-
llic state.
Brain death is defined as the irreversible
loss of all functions of the entire brain,
14
such
that the body is unable to maintain respiratory
and cardiovascular homeostasis. Although vig-
orous supportive care may keep the body pro-
cesses going for some time, particularly in an
Table 1–2 Terms Used to Describe
Disorders of Consciousness
Acute
Subacute or Chronic
Clouding
Dementia
Delirium
Hypersomnia
Obtundation
Abulic
Stupor
Akinetic mutism
Coma
Minimal consciousness
Locked in (not coma;
see text)
Vegetative
Brain death
8
Plum and Posner’s Diagnosis of Stupor and Coma