tion of the nervous system behaving according to
fundamental principles. Hence, the evaluation
of the comatose patient becomes an exercise in
applying those principles to the evaluation of a
human with brain failure.
Structural Lesions That Cause
Altered Consciousness in Humans
To produce stupor or coma in humans, a dis-
order must damage or depress the function of
either extensive areas of both cerebral hemi-
spheres or the ascending arousal system, includ-
ing the paramedian region of the upper brain-
stem or the diencephalon on both sides of the
brain. Figure 1–8 illustrates examples of such
lesions that may cause coma. Conversely, uni-
lateral hemispheric lesions, or lesions of the
brainstem at the level of the midpons or below,
do not cause coma. Figure 1–9 illustrates sev-
eral such cases that may cause profound sensory
and motor deficits but do not impair conscious-
ness.
Figure 1–8. Brain lesions that cause coma. (A) Diffuse hemispheric damage, for example, due to hypoxic-ischemic
encephalopathy (see Patient 1–1). (B) Diencephalic injury, as in a patient with a tumor destroying the hypothalamus.
(C) Damage to the paramedian portion of the upper midbrain and caudal diencephalon, as in a patient with a tip of the basilar
embolus. (D) High pontine and lower midbrain paramedian tegmental injury (e.g., in a case of basilar artery occlusion).
(E) Pontine hemorrhage, because it produces compression of the surrounding brainstem, can cause dysfunction that extends
beyond the area of the tissue loss. This case shows the residual area of injury at autopsy 7 months after a pontine hemorrhage.
The patient was comatose during the first 2 months.
Pathophysiology of Signs and Symptoms of Coma
29
BILATERAL HEMISPHERIC
DAMAGE
Bilateral and extensive damage to the cere-
bral cortex occurs most often in the context of
hypoxic-ischemic insult. The initial response to
loss of cerebral blood flow (CBF) or insuffi-
cient oxygenation of the blood includes loss of
consciousness. Even if blood flow or oxygena-
tion is restored after 5 or more minutes, there
may be widespread cortical injury and neuro-
nal loss even in the absence of frank infarc-
tion.
102,103
The typical appearance pathologi-
cally is that neurons in layers III and V (which
receive the most glutamatergic input from
other cortical areas) and in the CA1 region of
the hippocampus (which receives exten-
sive glutamatergic input from both the CA3
fields and the entorhinal cortex) demonstrate
eosinophilia in the first few days after the in-
jury. Later, the neurons undergo pyknosis and
apoptotic cell death (Figure 1–10). The net re-
sult is pseudolaminar necrosis, in which the
cerebral cortex and the CA1 region both are
depopulated of pyramidal cells.
Alternatively, in some patients with less ex-
treme cortical hypoxia, there may be a lucid
interval in which the patient appears to recover,
followed by a subsequent deterioration. Such a
patient is described in the historical vignette on
this and the following page. (Throughout this
book we will use historical vignettes to describe
cases that occurred before the modern era of
neurologic diagnosis and treatment, in which
the natural history of a disorder unfolded in a
way in which it would seldom do today. Fortu-
nately, most such cases included pathologic
assessment, which is also all too infrequent in
modern cases.)
HISTORICAL VIGNETTE
Patient 1–1
A 59-year-old man was found unconscious in a
room filled with natural gas. A companion already
had died, apparently the result of an attempted
double suicide. On admission the man was unre-
sponsive. His blood pressure was 120/80 mm Hg,
pulse 120, and respirations 18 and regular. His rectal
temperature was 1028F. His stretch reflexes were
hypoactive, and plantar responses were absent.
Coarse rhonchi were heard throughout both lung
fields.
He was treated with nasal oxygen and began to
awaken in 30 hours. On the second hospital day
he was alert and oriented. On the fourth day he was
afebrile, his chest was clear, and he ambulated.
The neurologic examination was normal, and an
evaluation by a psychiatrist revealed a clear senso-
rium with ‘‘no evidence of organic brain damage.’’
He was discharged to his relatives’ care 9 days
after the anoxic event.
At home he remained well for 2 days but then
became quiet, speaking only when spoken to. The
following day he merely shuffled about and res-
Figure 1–9. Lesions of the brainstem may be very
large without causing coma if they do not involve the
ascending arousal system bilaterally. (A) Even an
extensive infarction at the mesopontine level that
does not include the dorsolateral pons on one side
and leaves intact the paramedian midbrain can result
in preservation of consciousness. (B) Lesions at
a low pontine and medullary level, even if they in-
volve a hemorrhage, do not impair consciousness.
(Patient 1–2, p. 33)
30
Plum and Posner’s Diagnosis of Stupor and Coma
ponded in monosyllables. The next day (13 days
after the anoxia) he became incontinent and
unable to walk, swallow, or chew. He neither spoke
to nor recognized his family. He was admitted to a
private psychiatric hospital with the diagnosis of
depression. Deterioration continued, and 28 days
after the initial anoxia he was readmitted to the
hospital. His blood pressure was 170/100 mm Hg,
pulse 100, respirations 24, and temperature 1018F.
There were coarse rales at both lung bases. He per-
spired profusely and constantly. He did not re-
spond to pain, but would open his eyes momen-
tarily to loud sounds. His extremities were flexed
and rigid, his deep tendon reflexes were hyperac-
tive, and his plantar responses extensor. Laboratory
studies, including examination of the spinal fluid,
were normal. He died 3 days later.
An autopsy examination showed diffuse bron-
chopneumonia. The brain was grossly normal.
There was no cerebral swelling. Coronal sections
appeared normal with no evidence of pallidal ne-
crosis. Histologically, neurons in the motor cortex,
hippocampus, cerebellum, and occipital lobes ap-
peared generally well preserved, although a few
sections showed minimal cytodegenerative chan-
ges and reduction of neurons. There was occasional
perivascular lymphocytic infiltration. Pathologic
changes were not present in blood vessels, nor was
there any interstitial edema. The striking alteration
was diffuse demyelination involving all lobes of the
cerebral hemispheres and sparing only the arcuate
fibers (the immediately subcortical portion of the
cerebral white matter). Axons were also reduced in
number but were better preserved than was the
myelin. Oligodendroglia were preserved in demye-
linated areas. Reactive astrocytes were consider-
ably increased. The brainstem and cerebellum were
histologically intact. The condition of delayed post-
anoxic cerebral demyelination observed in this pa-
tient is discussed at greater length in Chapter 5.
Another major class of patients with bilateral
hemispheric damage causing coma is of those
Figure 1–10. Hypoxia typically causes more severe damage to large pyramidal cells in the cerebral cortex and hippo-
campus compared to surrounding structures. (A) shows a low magnification view of the cerebral cortex illustrating pseu-
dolaminar necrosis (arrow), which parallels the pial surface. At higher magnification (B), the area of necrosis involves
layers II to V of the cerebral cortex, which contains the large pyramidal cells (region between the two arrows). (C) At high
magnification, surviving neurons are pyknotic and eosinophilic, indicating hypoxic injury. Scale in A ¼ 8 mm, B ¼ 0.6 mm,
and C ¼ 15 micrometers.
Pathophysiology of Signs and Symptoms of Coma
31