In a series of 62 adults with community-
acquired acute bacterial meningitis admitted to
an intensive care unit, 95% had impaired con-
sciousness.
However, the classic triad of fever, nuchal
rigidity, and alteration of mental status was
present in only 44% of patients in a large series
ofcommunity-acquiredmeningitis.
83
Focalneu-
rologic signs were present in one-third and in-
cluded cranial nerve palsies, aphasia, and hemi-
paresis; papilledema was found in only 3%.
Subacute or chronic meningitis runs an in-
dolent course and may be accompanied by the
same symptoms, but also may occur in the
absence of fever in debilitated or immune-
suppressed patients. Both acute and chronic
meningitis may be characterized only by leth-
argy, stupor, or coma in the absence of the
other common signs. Chronic meningitis (e.g.,
with tuberculosis or cryptococcus) can also
cause a local arteritis, resulting in cranial nerve
dysfunction and focal areas of CNS infarc-
tion.
88
Aspergillus meningitis, which is typically
seen only in patients who have been immune
suppressed, causes a hemorrhagic arteritis,
which may produce a combination of focal
findings and impaired consciousness. How-
ever, the impairment of consciousness in each
of these cases is primarily due to the immuno-
logic processes concerned with the infection
rather than structural causes (see Chapter 5).
The examination should include careful
evaluation of nuchal rigidity even in patients
who are stuporous. Attempting to flex the neck
in a patient with meningitis may lead to gri-
macing and a rapid flexion of knees and hips
(Brudzinski sign). Lateral movement of the
neck, such as in eliciting the doll’s head/eye
signs, is not resisted. If one flexes the thigh to
the right angle with the axis of the trunk, the
patient grimaces and resists extension of the
leg on the thigh (Kernig sign). Pain with jolt
accentuation (the patient turns the head hor-
izontally at two to three cycles per second) is a
very sensitive sign of meningismus (positive in
97% of patients with meningitis) if the patient
is sufficiently awake to cooperate, but is non-
specific (positive in 40% of patients with sus-
pected meningitis, but no pleocytosis in the
CSF).
89
Examination of the nose and ears for
CSF discharge, and of the back for a CSF-
to-skin sinus tract, may aid in the diagnosis.
CSF can be distinguished from other clear fluid
discharges at the bedside by its containing glu-
cose. Measurement of beta-trace protein in the
blood and discharge fluid is more accurate.
90
Meningitis, particularly in children, can cause
acute brain edema with transtentorial hernia-
tion as the initial sign. Clinically, such children
rapidly lose consciousness and develop hyper-
pnea disproportionate to the degree of fever.
The pupils dilate, at first moderately and then
widely, then fix, and the child develops decer-
ebrate motor signs. Urea, mannitol, or other hy-
perosmotic agents, if used properly, can prevent
or reverse the full development of the ominous
changes that are otherwise rapidly fatal.
In elderly patients, bacterial meningitis
sometimes presents as insidiously developing
stupor or coma in which there may be focal
neurologic signs but little evidence of severe
systemic illness or stiff neck. In one series, 50%
of such patients with meningitis were admitted
to the hospital with another and incorrect di-
agnosis.
91,92
Such patients can be regarded in-
correctly as having suffered a stroke, but this
error is readily avoided by accurate spinal
fluid examinations.
If meningitis is suspected, a lumbar punc-
ture is essential. Whether it should be per-
formed before or after a CT scan is contro-
versial.
33,93,94
Some observers believe that the
diagnostic value warrants the small but definite
risk. Many physicians believe that a CT scan
cannot determine the safety of a lumbar punc-
ture. Many patients with either supratento-
rial or infratentorial mass lesions tolerate lum-
bar puncture without complication; conversely,
some patients with apparently normal CT may
Table 4–3 Clinical Findings in
103 Patients With Acute Bacterial
Meningitis
Symptom
%
Fever
97*
Nuchal rigidity
87
Headache
66
Nausea/vomiting
55
Confusion
56
Altered consciousness
51
Seizures
25
Focal signs
23
Papilledema
2
*Not all patients were examined for each finding.
Data from Hussein and Shafran.
87
Specific Causes of Structural Coma
133
herniate. Most who want to perform CT first
argue that when there is a strong suspicion of
acute bacterial meningitis, one can begin an-
tibiotics before the CT scan if the tap is done
promptly after an emergent CT; Gram stain
and cultures may still be positive. They further
argue that the presence of a mass lesion sug-
gests that the neurologic signs are not a result
of meningitis alone and that lumbar puncture is
probably unnecessary. Finally, even in the ab-
sence of a mass lesion, obliteration of the peri-
mesencephalic cisterns or descent of the ton-
sils below the foramen magnum is a major risk
factor for the development of herniation after a
lumbar puncture. In such cases, lumbar punc-
ture should be deferred until hyperosmolar
agents (see Chapter 7) decrease the ICP. Re-
gardless of which approach is taken, it is crit-
ical for the diagnostic evaluation not to prevent
the immediate drawing of blood cultures, fol-
lowed by administration of appropriate anti-
biotics.
In acute bacterial meningitis, CSF pres-
sure at lumbar puncture is usually elevated. A
normal or low pressure raises the question of
whether there has already been partial herni-
ation of the cerebellar tonsils. The cell count
and protein are elevated, and glucose may be
depressed or normal. Examination for bacte-
rial antigens sometimes is diagnostic in the ab-
sence of a positive culture. Examination of the
spinal fluid helps one differentiate acute bac-
terial meningitis from acute aseptic meningi-
tis (Table 4–4). Because S. pneumoniae and
N. meningitidis are the most common causal
organisms, empiric therapy in adults should
include either ceftriaxone (4 g/day in divided
doses every 12 hours), cefotaxime (up to 8 to
12 g/day in divided doses every 4 to 6 hours),
or cefepime (4 to 6 g/day in divided doses
every 8 to 12 hours); vancomycin should be
added until the results of antimicrobial sus-
ceptibility testing are known. In elderly pa-
tients and those who are immune suppressed,
L. monocytogenes and H. influenzae play a
role, and ampicillin should be added to those
drugs. Meropenem may turn out to be an at-
tractive candidate for monotherapy in elderly
patients. In a setting where Rocky Mountain
spotted fever or ehrlichiosis are possible in-
fectious organisms, the addition of doxycycline
is prudent.
Whether corticosteroids should be used is
controversial. Adjuvant dexamethasone is re-
commended for children and adults with hae-
mophilus meningitis or pneumococcal menin-
gitis but is not currently recommended for
the treatment of Gram-negative meningitis.
Table 4–4 Typical Cerebrospinal Fluid (CSF) Findings in Bacterial Versus
Aseptic Meningitis
CSF Parameter
Bacterial Meningitis
Aseptic Meningitis
Opening pressure
>
180 mm H
2
O
Normal or slightly elevated
Glucose
<
40 mg/dL
<
45 mg/dL
CSF-to-serum glucose ratio
<
0.31
>
0.6
Protein
>
50 mg/dL
Normal or elevated
White blood cells
>
10 to <10,000/mm
3
—neutrophils
predominate
50–2,000/mm
3
—lymphocytes
predominate
Gram stain
Positive in 70%–90% of untreated
cases
Negative
Lactate
!3.8 mmol/L
Normal
C-reactive protein
>
100 ng/mL
Minimal
Limulus lysate assay
Positive indicates Gram-negative
meningitis
Negative
Latex agglutination
Specific for antigens of Streptococcus
pneumoniae, Neisseria meningitidis
(not serogroup B), and Hib
Negative
Coagglutination
Same as above
Negative
Counterimmunoelectrophoresis
Same as above
Negative
From Roos et al.,
95
with permission
134
Plum and Posner’s Diagnosis of Stupor and Coma