Page 922 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

CHAPTER 71: Bacterial Infections of the Central Nervous System 653

remote head injury and CSF leak are important predisposing factors found in two-thirds of patients, but all had at least one of these find-
for recurrent bacterial meningitis. In one study of 352 episodes of ings. In another review of 696 cases of community-acquired bacterial
14
community-acquired pneumococcal meningitis in adults, 70% of episodes meningitis, the triad of fever, neck stiffness, and altered mental status
25
were associated with an underlying disorder and the overall in-hospital was found in only 44% of episodes, although almost all patients (95%)
mortality rate was 30%. Rates of pneumococcal meningitis have been presented with at least two of four symptoms (headache, fever, stiff neck,
15
reported to decrease among children and adults since introduction of the altered mental status). Also seen are nausea, vomiting, rigors, profuse
heptavalent pneumococcal conjugate vaccine, although there has been sweating, weakness, and myalgias. The meningismus may be subtle or
16
an increase in meningitis caused by nonvaccine serotypes. A 13-valent marked or accompanied (rarely) by the Kernig and/or Brudzinski signs.
pneumococcal conjugate vaccine, which covers some of these additional The Kernig sign is elicited by flexing the thigh on the abdomen with the
serotypes, has recently been licensed and recommended for use. 17 knee flexed; the leg is then passively extended, and, if there is meningeal
Listeria monocytogenes accounts for only about 3% of all cases of bac- inflammation, the patient resists leg extension. The Brudzinski sign is
terial meningitis in the United States, but carries a high mortality rate. present when passive flexion of the neck leads to flexion of the hips
4,5
Infection with Listeria is more likely in neonates, the elderly, alcoholics, and knees. However, these signs are elicited in fewer than 5% of cases
cancer patients, and immunosuppressed adults (eg, renal transplant of bacterial meningitis in adults, indicating that they do not accurately
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patients). 18,19 Cases have also been reported in patients receiving anti- distinguish patients with meningitis from those without meningitis.
tumor necrosis factor α agents (eg, infliximab and etanercept). Listeria Cerebral dysfunction is manifested by confusion, delirium, or a declin-
meningitis is found infrequently in patients with human immunodefi- ing level of consciousness ranging from lethargy to coma. Cranial nerve
ciency virus infection, despite its increased incidence in patients with palsies (especially involving cranial nerves III, IV, VI, and VII) and focal
deficiencies in cell-mediated immunity. However, up to 30% of adults cerebral signs are uncommon (10%-20% of cases). Seizures occur in
and 54% of children and young adults with listeriosis have no appar- about 30% of all cases. Papilledema is rare (<5%) and should suggest an
ent underlying condition. Listeriosis has been associated with several alternate diagnosis, such as an intracranial mass lesion. To further char-
food-borne outbreaks involving contaminated cole slaw, milk, cheese, acterize the accuracy and precision of the clinical examination in adult
and processed meats. In recent years, the incidence of invasive disease patients with acute meningitis, data from 845 episodes were reviewed
caused by L monocytogenes has been decreasing, likely as a result a and demonstrated that individual items of the clinical history (ie, head-
decrease in organism contamination in ready-to-eat food. 20 ache, nausea, and vomiting) had a low accuracy for the diagnosis of
Meningitis due to aerobic gram-negative bacilli is observed in specific acute meningitis; on review of the physical examination, the absence
clinical situations. 13,21 Escherichia coli is isolated in 30% to 50% of infants of fever, neck stiffness, and altered mental status effectively eliminated
younger than 2 months with bacterial meningitis. Klebsiella species, the likelihood of acute meningitis (sensitivity 99%-100% for the pres-
E coli, and Pseudomonas aeruginosa may be isolated in patients who ence of one of these findings in diagnosis). However, despite these
27
have had head trauma or neurosurgical procedures, in the elderly, results, physicians should have a low threshold for performing a lumbar
in immunosuppressed patients, and in patients with gram-negative puncture in patients with suspected bacterial meningitis. Late in the
bacteremia. Some cases have been associated with disseminated disease, patients may develop signs of increased intracranial pressure,
strongyloidiasis in the hyperinfection syndrome, in which meningitis including coma, hypertension, bradycardia, and third-nerve palsy; these
is caused by enteric bacteria due to seeding of the meninges during findings are ominous prognostic signs.
persistent bacteremia associated with migration with infected larvae; Certain symptoms and signs may suggest an etiologic diagnosis in
alternatively, larvae may carry enteric organisms on their surfaces or patients with bacterial meningitis. Persons with meningococcemia
21
within their own gastrointestinal tracts as they exit the gut and invade present with a prominent rash, principally on the extremities (∼50%
the meninges. of cases). Early in the disease course, the rash may be erythematous
Specific clinical situations also predispose to the development of and macular, but it quickly evolves into a petechial phase, with further
meningitis due to staphylococcal species. Staphylococcus epidermidis coalescence into a purpuric form. The rash often matures rapidly, with
is the most common cause of meningitis in persons with CSF shunts. new petechial lesions appearing during the physical examination. A
13
Meningitis due to Staphylococcus aureus is frequently found (when petechial, purpuric, or ecchymotic rash may also be seen in other forms
compared with other pathogens) after head trauma or soon after neuro- of meningitis (ie, those due to echovirus type 9, Acinetobacter species,
surgery, or in those with infective endocarditis or paraspinal infection. S aureus, and, rarely, S pneumoniae or H influenzae), in Rocky
22
Underlying diseases among persons with no prior CNS disease who Mountain spotted fever or S aureus endocarditis, and in overwhelm-
develop S aureus meningitis include diabetes mellitus, alcoholism, ing sepsis (due to S pneumoniae or H influenzae) in splenectomized
chronic renal failure requiring hemodialysis, and malignancies. patients. An additional suppurative focus of infection (eg, otitis media,
Conditions that increase S aureus nasal carriage rates (eg, injection drug sinusitis, or pneumonia) is present in 30% of patients with pneumococ-
abuse, insulin-requiring diabetes, and hemodialysis) may also predis- cal or H influenzae meningitis but is rarely found in meningococcal
pose to staphylococcal infection of the CNS. meningitis. Meningitis due to S pneumoniae is relatively likely after
Group B streptococcus (Streptococcus agalactiae) is a common cause head trauma in persons who have basilar skull fractures in which a
of meningitis in neonates 21,23 ; 66% of all cases have been reported during dural fistula is produced between the subarachnoid space and the nasal
the first 3 months of life. The risk of transmission from the mother to cavity, paranasal sinuses, or middle ear. These persons commonly
10
her infant is increased when the inoculum of organisms and number of present with rhinorrhea or otorrhea due to a CSF leak; a persistent
sites of maternal colonization are large; horizontal transmission has also defect is a common explanation for recurrent bacterial meningitis.
been documented from the hands of nursery personnel to the infant. Patients with Listeria meningitis have an increased tendency to have
Risk factors for group B streptococcal meningitis in adults include age seizures and focal neurologic deficits early in infection and may pres-
older than 60 years, diabetes mellitus, parturient status in women, car- ent with other features consistent with rhombencephalitis (ie, ataxia,
diac disease, collagen vascular disease, malignancy, alcoholism, hepatic cranial nerve palsies, or nystagmus). 18,19
failure, renal failure, and corticosteroid therapy. No underlying illnesses Certain subgroups of patients may not manifest the classic signs
were found in 43% of patients in one review. 24 and symptoms of bacterial meningitis. Usually in a neonate there is
21
■ CLINICAL PRESENTATION no meningismus or fever, and the only clinical clues to meningitis are
listlessness, high-pitched crying, fretfulness, refusal to feed, irritability,
The classic clinical presentation in adults with bacterial meningitis includes vomiting, diarrhea, respiratory distress, seizures, or bulging fontanelle.
28
fever, headache, meningismus, and signs of cerebral dysfunction. Elderly patients, especially those with underlying conditions such as
21
In one review of 493 cases of acute bacterial meningitis in adults, the diabetes mellitus or cardiopulmonary disease, may present with insidi-
2
triad of fever, nuchal rigidity, and change in mental status was only ous disease manifested only by lethargy or obtundation, variable signs

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