Cerebral abscess, 324.0
Encephalitis, 323.9
Encephalopathy, 348.30
Meningitis, 322.9
I. Definition
A. Inflammation of the pia mater and arachnoid of the brain or spinal cord
II. Etiology/predisposing factors
A. Predisposing factors for the development of community-acquired meningitis include preexisting diabetes mellitus, otitis media, pneumonia, sinusitis, and alcohol abuse.
B. Bacterial meningitis
1. Profound and life threatening
2. Meninges attempt to destroy the microorganism that entered the CNS.
3. Neutrophils gather in the area and begin making exudates within the subarachnoid space.
4. Exudate causes the CSF to thicken and decreases the flow of CSF through the brain and spinal cord.
a. Streptococcus pneumoniae (pneumococcal meningitis)
i. Most common and most serious (may cause neurologic damage ranging from deafness to severe brain damage) bacterial meningitis
ii. Occurs frequently in infants (younger than age 2), adults with weakened immune systems, and the elderly
iii. Rates in children younger than age 2 have decreased since the pneumococcal 7-valent conjugate vaccine (Prevnar) has been available.
c. Haemophilus influenzae
i. At one time, this was the most common cause of acute bacterial meningitis.
ii. H. influenzae B (Hib) vaccine has greatly reduced the number of cases in the US.
iii. Children most at risk are those in daycare and children who do not have access to the vaccine.
d. Escherichia coli, and Enterobacter, Klebsiella, and Proteus spp
i. May occur in infants, the elderly, and immunosuppressed patients
e. Other bacterial meningitides (less common)
i. Listeria monocytogenes
ii. Staphylococci (Staphylococcus aureus and Staphylococcus epidermidis)
iii. Mycobacterium tuberculosis
iv. Streptococci
f. Meningitis may follow an upper respiratory infection or head trauma.
C. Aseptic or viral meningitis
1. Pia and arachnoid space are filled with lymphocytes but not with exudate forms.
2. Much more benign and self-limited than bacterial meningitis
3. Caused by viruses
a. Mumps
b. Enterovirus
c. Influenza
d. Varicella zoster
e. Herpes simplex types 1 and 2
f. Adenovirus
g. Epstein-Barr virus
h. Human immunodeficiency virus (HIV)
4. Fungal
a. Most common in immunocompromised (particularly in patients with AIDS)
b. Candida albicans
c. Coccidioides immitis
D. Syphilis
III. Clinical manifestations
A. Fever of 101° F to 103° F (38° C to 40° C); toxic appearance
B. Stiff neck (nuchal rigidity) related to meningeal irritation
C. Altered sensorium
D. Severe headache
E. Photophobia, may have diplopia
F. Chills, myalgias
G. Kernig’s sign
1. Flex the patient’s leg at the knee, then at the hip, to a 90-degree angle, and extend the knee.
2. In a patient with meningitis, this maneuver will trigger pain and spasms of the hamstring muscles caused by inflammation of the meninges and spinal nerve roots.
H. Brudzinski’s sign
1. Flex the patient’s head and neck to the chest.
2. The legs will flex at the hips and at the knees in response to this movement.
I. Nausea and vomiting
J. Purpura or petechiae: may be seen with meningococcal meningitis
K. Ear, nose, and throat (ENT): may have deafness and vertigo (cranial nerve [CN] VIII)
L. Neurologic: may have exaggerated deep tendon reflexes (DTRs), seizures, unilateral or bilateral sensory loss
IV. Laboratory findings/diagnostics
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A. Lumbar puncture should be performed as soon as a diagnosis is suspected, except in individuals with a suspected space-occupying lesion (brain abscess, subdural hematoma, subdural abscess).
B. Lumbar puncture in bacterial meningitis
1. Appearance of CSF: cloudy
2. Opening pressure: elevated (greater than 180 mm H2O)
3. Cells: increased WBCs (1000-2000/mm; most are polymorphonuclear cells)
4. Total protein: increased (100-500 mg/dl [normal, 15-45 mg/dl])
5. Glucose: decreased (less than 40 mg/dl or 40% of glucose [normal, 60%-80%])
6. Culture: bacteria present on Gram’s stain and culture
C. Lumbar puncture in viral meningitis
1. Appearance of CSF: clear, occasionally cloudy
2. Opening pressure: usually normal (less than 30 mm H2O)
3. Cells: increased WBCs (300/mm3; most are mononuclear cells)
4. Total protein: normal or slightly increased
5. Glucose: normal
D. CT scan of the head is indicated in patients with focal neurologic signs or diminished level of consciousness.
E. In patients who have signs and symptoms and CSF findings typical of bacterial meningitis, but in whom no organisms are found, follow-up CT scans should be obtained, even if clinical improvement occurs, because such patients may have a brain abscess and may require neurosurgical intervention.
F. An additional maneuver in assessing for meningitis is to elicit jolt accentuation of the patient’s headache by asking the patient to turn his or her head horizontally at a frequency of two to three rotations per second.
1. Worsening of a baseline headache is a positive sign.
2. Include examination of the cranial nerves, motor and sensory systems, and reflexes, as well as testing for Babinski’s reflex.
G. Assess the ears, sinuses, and respiratory system.
H. Obtain blood cultures.
I. Obtain CBC, electrolytes, and liver/renal panel.
J. Chest, skull, and sinus films or chest CT scan may be necessary to facilitate detection of primary infection.
K. Latex agglutination tests
1. Can detect antigens of encapsulated organisms such as S. pneumoniae, H. influenzae, N. meningitides, and C. neoformans
2. Rarely used, except for detection of Cryptococcus or in partially treated patients
L. Polymerase chain reaction (PCR) testing of CSF
1. Has been employed to detect bacteria (S. pneumoniae, H. influenzae, N. meningitides, M. tuberculosis, Borrelia burgdorferi, and Tropheryma whippelii) and viruses (herpes simplex, varicella-zoster, cytomegalovirus, Epstein-Barr virus, and enterovirus) in patients with meningitis
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