Even in those patients who are not comatose
on admission, alterations of consciousness may
develop in the ensuing days. Deterioration may
occur due to rebleeding, which is particularly
common in the first 24 to 48 hours. About 3 to 7
days after the hemorrhage, cerebral vasospasm
may occur.
65
Vasospasm typically develops first
and is most intense in the area of the greatest
amount of extracerebral clot. This delayed ce-
rebral ischemia may result in brain infarction
and further edema, thus exacerbating the im-
pairment of consciousness. Acutely develop-
ing hydrocephalus
66
from obstruction of spinal
fluid pathways may also impair consciousness.
The patient should be observed carefully for
these complications and appropriate treatment
applied.
65,66
Subarachnoid Tumors
Both benign and malignant tumors may invade
the subarachnoid space, infiltrating the lepto-
meninges either diffusely or focally and some-
times invading roots, or growing down the
Virchow-Robin spaces to invade the brain.
Leptomeningeal tumors include lymphomas
and leukemias and solid tumors such as breast,
renal cell, and lung cancers, as well as medul-
loblastomas and glial tumors.
67–69
The hallmark
of meningeal neoplasms is multilevel dysfunc-
tion of the nervous system, including signs of
damage to cranial or spinal nerves, spinal cord,
brainstem, or cerebral hemispheres. Many pa-
tients with meningeal carcinoma have impair-
ment of consciousness that is difficult to ex-
plain on the basis of the distribution of the
tumor cells. The cause of the depressed level
of consciousness in these patients is not clear.
Explanations have included hydrocephalus
from obstruction of spinal fluid pathways,
70,71
invasion of the brain along the Virchow-Robin
spaces of penetrating pial vessels (the so-called
encephalitic form of metastatic carcinoma),
72
nonconvulsive status epilepticus,
73
interference
by the tumor with cortical metabolism,
74,75
or
an immunologic response to the tumor
76
with
production of cytokines and prostaglandins;
most patients also have some white blood cells
in their CSF as well as tumor cells.
The diagnosis of subarachnoid tumor is chal-
lenging, particularly when the multilevel dys-
functions of the nervous system are the first
signs of the tumor. The MRI scan may show
tumor implants in the leptomeninges or on the
surface of the brain, or it may demonstrate
thickening of cranial nerve or spinal roots (Fig-
ure 4–5). If the scan is negative, the diagnosis
is established by the presence of tumor cells
77
or tumor markers
78
in the spinal fluid. How-
ever, the clinician must think of the diagnosis
to perform these tests. Fortunately, there are
nearly always other abnormalities in the CSF
(lymphocytes, low glucose, elevated protein),
which may lead to repeat examination if the
first cytology is negative, as CSF cytology has
a low degree of sensitivity. Wasserstrom and
colleagues found that in patients with patholog-
ically demonstrated meningeal carcinoma or
lymphoma, only 40% of the first CSF samples
contained malignant cells.
79
Although the diagnosis of meningeal cancer
generally indicates a poor prognosis, there are
occasional patients with leukemia, lymphoma,
or breast cancer in whom vigorous treatment of
the meningeal tumor may result in marked im-
provement or even complete remission. Treat-
ment usually includes high-dose intravenous
80
or intraventricular chemotherapy, as well as ir-
radiation of areas of focal central nervous sys-
tem (CNS) dysfunction (but not the entire
neuraxis).
81
Subarachnoid Infection
Subarachnoid infection (i.e., meningitis) is a
common cause of impaired consciousness.
Meningitis can be either acute or chronic and
can be caused by a variety of different organ-
isms including bacteria, fungi, rickettsiae, and
viruses. Neurologic signs and symptoms caused
by meningitis vary depending on the acuity of
the infection and the nature of the infecting
organisms, but certain aspects are common to
all. For organisms to cause meningitis, they
must first invade the meninges. This is usually
done via the bloodstream, and for this reason
blood cultures will often identify the organism.
Less commonly, meningitis is a result of spread
of organisms from structures adjacent to the
brain (sinusitis, otitis). Meningitis can also occur
in the absence of sepsis if there is communi-
cation between the meninges and the surface
(CSF fistula, head injury, neurosurgery). Once
in the meninges, organisms multiply, inducing
the macrophage system that lines the menin-
ges and superficial blood vessels in the brain
Specific Causes of Structural Coma
131
to produce a variety of cytokines and other
proinflammatory molecules that in turn attract
other white cells to the meninges. The inflam-
matory reaction can disrupt the blood-brain
barrier; obstruct spinal fluid absorptive path-
ways, causing hydrocephalus and cellular swell-
ing; or cause a vasculitis of subarachnoid or
penetrating cortical blood vessels with result-
ing cerebral ischemia or infarction. Inflamma-
tory reactions also cause metabolic disturbances
that lower the pH, promoting vasodilation and
increasing cerebral blood volume, leading to
increased ICP.
82
Thus, although the infection
itself does not cause a supratentorial mass, the
combination of vasogenic and cytotoxic edema
caused by the inflammatory response may pro-
duce enough diffuse mass effect to cause her-
niation. Both transtentorial and tonsillar herni-
ation may occur, although both are rare.
The major causes of community-acquired
bacterial meningitis include Streptococcus
pneumoniae (51%) and Neisseria meninigitis
(37%).
83
In immunocompromised patients,
Listeria monocytogenes meningitis accounts for
about 4% of cases.
84–86
Listeria meningitis may
be noticeably slower in its course but has a
tendency to cause brainstem abscesses. Staph-
ylococcus aureus and, since a vaccine became
available, Haemophilus influenzae are uncom-
mon causes of community-acquired men-
ingitis.
83
Acute bacterial meningitis is a medical emer-
gency, as treated patients can die within hours
of onset. Viral meningitis may clinically mimic
bacterial meningitis, but in most cases are self-
limiting. The clinical signs of acute bacterial
meningitis are headache, fever, stiff neck, pho-
tophobia, and an alteration of mental status.
Focal neurologic signs can occur either from
ischemia of underlying brain or from damage
to cranial nerves as they pass through the sub-
arachnoid space. In a series of adults with
acute bacterial meningitis,
87
97% of patients
had fever, 87% nuchal rigidity, and 84% head-
ache. Nausea or vomiting was present in 55%,
confusion in 56%, and a decreased level of
consciousness in 51%. Papilledema was iden-
tified in only 2% of patients, although it was
not tested in almost half. Seizure activity oc-
curred in 25% of patients, but was always within
24 hours of the clinical diagnosis of acute
meningitis. Over 40% of the patients had been
partially treated before the diagnosis was es-
tablished, so that in 30% of patients neither
Gram stain nor cultures were positive. Eigh-
teen percent of the patients died (Table 4–3).
Figure 4–5. A pair of images from a magnetic resonance imaging (MRI) scan with contrast in a patient with meningeal
lymphoma. This 52-year-old man presented with bilateral visual distortion and some left leg weakness. Both chronic lym-
phocytic leukemia and a non-Hodgkin’s lymphoma had recently been diagnosed. The MRI scan showed superficial en-
hancement outlining the cortical sulci (arrows).
132
Plum and Posner’s Diagnosis of Stupor and Coma