However, as many as one-half of the patients
presenting with grades I or II deteriorate
from vasospasm, rebleeding, hydrocephalus,
or brain edema. About 10% (range 3% to 17%)
of patients die before reaching medical atten-
tion and another 10% prior to hospital evalu-
ation. The overall mortality is 40% to 50%.
53
GCS is a good predictor of outcome from
SAH if the patient’s age, the amount of blood on
CT scan, the location of the aneurysm (worse
for posterior circulation sites compared with
anterior circulation),
53
and secondary compli-
cations following the initial rupture are also fac-
tored in. A high percentage of patients with
grades IV and V die from secondary complica-
tions if they remain in coma for 2 weeks or more.
Rebleeding of an aneurysm causing coma
and depression or loss of brainstem reflexes
carries a mortality rate of 50%. In one study,
bilateral loss of pupillary responses carried a
95% mortality rate. Electrophysiologic mea-
surements have also shown some utility in the
prognosis of SAH; loss of BAERs and SSEPs
correlate with poor grades on examination.
54,55
Central Nervous System Infection
Coma was present on admission in 14% of 696
patients with bacterial meningitis
56
(see also
page 262). Obtundation on admission was a
significant risk factor for death or a GOS less
than 4, as were age older than 60 years, hy-
potension, seizures within 24 hours (often as-
sociated with a low serum sodium), and cere-
brospinal fluid (CSF) abnormalities including
decreased glucose concentration or elevation
of the CSF protein (greater than or equal to
250 mg/dL). In most cases, death was a result
of herniation, occasionally following an ill-
advised lumbar puncture. Some investigators
have suggested that the presence of coma is
the best predictor of morbidity from acute
meningitis.
57
Coma is often the result of in-
creased ICP resulting from alteration of the
blood-barrier by toxins (vasogenic edema), im-
paired resorption of CSF (interstitial edema),
or venous or arterial occlusions (infarction
with cytotoxic edema).
58
A brain abscess caus-
ing coma also has a poor prognosis (GOS less
than 4)
59
; herniation is the principal cause of
coma with a 60% mortality rate.
60
Acute Disseminated
Encephalomyelitis
Acute disseminated encephalomyelitis (ADEM)
(see also page 366) is a monophasic autoimmune
demyelinating disease most commonly affect-
ing children and young adults that follows viral
or bacterial illnesses or may arise postvacci-
nation.
61
Although prognosis for ADEM has
historically been considered poor, current ex-
perience reflects that most patients (range 55%
to 90% across studies) will recover fully or with
minor neurologic disabilities. The improved
prognosis may reflect either the increased fre-
quency of diagnosis of relatively mild cases,
which often can be demonstrated on magnetic
resonance imaging (MRI), or perhaps the ten-
dency to treat patients with corticosteroids. Most
patients with ADEM improve within 6 months,
although many documented cases showed lon-
ger recovery times.
Hepatic Coma
Hepatic coma develops either as an inexor-
able stage in progressive hepatic failure or as a
more reversible process in patients with portal
systemic shunts when increased loads of ni-
trogenous substances are suddenly presented
into the circulation (see Chapter 5). Prognosis
in hepatic coma depends on the cause, the
acuteness and severity of the liver failure, and
the presence or absence of dysfunction of other
organs. The prognosis is far worse in fulminant
Table 9–10 Grading System for
Subarachnoid Hemorrhage
Grade
GCS Score
Presence of any
Motor Deficit
I
15
None
II
14–15
None
III
14–13
Present
IV
12–7
Present or absent
V
6–3
Present or absent
World Federation of Neurological Surgeons score is in-
dexed by Glasgow Coma Scale (GCS) and evidence of
identifiable motor deficits.
From the World Federation of Neurological Surgeons,
51
with permission
356
Plum and Posner’s Diagnosis of Stupor and Coma
hepatic failure than in coma associated with
chronic cirrhosis or portacaval shunting. Among
patients with nontraumatic coma, those with
hepatic encephalopathy demonstrated the best
chance for recovery (33%).
4
Survival also correlates with age in patients
with infectious and serum hepatitis. Patients
with chronic hepatocellular disease often drift
in and out of encephalopathy, a situation that
can be managed by correction of intercurrent
processes such as infection or reduction of cir-
culating nitrogenous load. If no exogenous fac-
tor can be identified, the presence of enceph-
alopathy is far more ominous and correlates
with high mortality; approximately 50% of pa-
tients with cirrhosis die within 1 year of dem-
onstrating encephalopathy.
62
Depressant Drug Poisoning
Most fatal intentional depressant drug poi-
sonings occur outside the hospital. Once such
patients reach treatment, experienced centers
worldwide generally report an overall mortal-
ity among patients with altered consciousness
of less than 1% (Table 9–7). The death rate
climbs to approximately 5% in those with grade
3 to 4 coma. The mortality can be substantially
higher when institutions treat only small num-
bers of patients or lack experience or proper
facilities. Adverse prognostic factors in depres-
sant drug coma include an advanced age, the
presence of complicating medical illnesses (es-
pecially systemic infections, hepatic insuffi-
ciency, and heart failure), and lengthy coma.
Alkaline diuresis (for phenobarbital), hemodi-
alysis, and charcoal hemoperfusion all have
been reported to shorten coma and improve
prognosis for patients with severe poisoning,
especially from phenobarbital. Barring unex-
pected complications, patients recovering from
depressant drug poisoning suffer no residual
brain damage even after prolonged coma last-
ing 5 days or more. Rare exceptions to this rule
occur in overdose patients who suffer aspira-
tion pneumonia or cardiac arrest (e.g., during
tracheal or gastric intubation). A small number
of patients develop cutaneous pressure sores
or pressure neuropathies from prolonged pe-
riods of immobility during the period of im-
mobile coma before the victim is found and
brought to hospital; this may be particularly
common with barbiturate overdoses.
VEGETATIVE STATE
The vegetative state (also called coma vigil or
apallic state) denotes the recovery of a crude
cycling of arousal states heralded by the ap-
pearance of ‘‘eyes-open’’ periods in an unre-
sponsive patient.
63
Very few patients remain in
eyes-closed coma for more than 10 to 14 days;
vegetative behavior usually replaces coma by
that time. Patients in VS, like comatose patients,
show no evidence of awareness of self or their
environment, but do retain brainstem regula-
tion of cardiopulmonary function and visceral
autonomic regulation. The term persistent
vegetative state is now commonly reserved for
patients remaining in that state for at least 30
days (see ANA Committee on Ethical Affairs
1993). As indicated in the paragraphs below,
there are no clear criteria for determining when
PVS becomes permanent.
One reason for the inability to predict per-
manence early in the course of PVS is that
patients usually have badly damaged cerebral
hemispheres combined with a relatively in-
tact brainstem. Such a combination during the
early days of illness causes coma with relatively
good brainstem function, a picture similar to
patients with reversible cerebral injury.
Since the publication of the third edition
of Stupor and Coma, guidelines to aid con-
struction of prognosis in VS have advanced
greatly.
64–66
The Multisociety Task Force on
PVS,
64,65
a joint commission composed of neu-
rologists, neurosurgeons, and other specialists,
organized a comprehensive review of outcomes
of patients with prolonged VS using GOS cri-
teria. Outcomes of 434 adult and 106 pediatric
patients with TBI and 169 adult and 45 pedi-
atric patients with nontraumatic etiologies
were assessed. Figure 9–4 displays data from
the TBI group for adults. For patients in VS
for at least 1 month, 52% had recovered con-
sciousness at 1 year postinjury (some 33% of the
patients had recovered earlier than 3 months
from the time of injury). If adult TBI patients
remained in VS at 3 months, the percentage
recovering consciousness at 1 year dropped
to 35%, and to 16% for VS lasting at least 6
months. For pediatric patients with a TBI-
induced VS for 1 month, 62% recovered con-
sciousness at 1 year; if VS persisted for 3
months, this percentage dropped only to 56%,
and to 32% for patients in VS for at least 6
Consciousness, Mechanisms Underlying Outcomes, and Ethical Considerations
357