• These are among the most important problems in
• Common acute infections of the nervous system include:
Acute bacterial meningitis
• Each may present with a non-specific prodrome of fever
• Inflammatory process of leptomeninges and CSF within the
• Meningoencephalitis combines this with inflammation of brain
• Meningitis is usually caused by
a infection - Acute pyogenic
(bacterial)or aseptic (viral) and
Chronic(usually due to tuberculous,
spirochetal or cryptococcal).
• Acute purulent infection
within the subarachnoid
• Associated with CNS
inflammatory reactions that
may result in decreased
consciousness, seizures, raised
• Usually present with
headache, fever and signs of
meningeal irritation coupled
with inflammatory CSF.
• The headache of viral
meningitis is often frontal or
retro-orbital associated with
photophobia and pain on
• Laboratory examination of the CSF is usually the first
step to confirm the presence of meningitis.
• Cytological examination should precede
centrifugation and heating of CSF.
• The typical profile:
CSF opening pressure: 50–180 mmH2O
Glucose: 40–85 mg/dL.
Protein (total): 15–45 mg/dL.
Leukocytes (WBC): 0–5/µL (adults / children); up to 30/µL
Gross appearance: Normal CSF is clear and colorless.
Differential: 60–70% lymphocytes; up to 30% monocytes
and macrophages; other cells 2% or less.
Normal (> 40 mg/dL.)
<100 mg/dL (moderate increase)
< 100 cells/µL.
Early: neutrophils. Late: lymphocytes.
Normal to marked decrease. <40 mg/dL.
(Marked increase) > 250 mg/dL.
>500 (usually > 1000). Early: May be < 100.
Predominance of Neutrophils (PMNs)
• Neutrophils fill the subarachnoid space in severely affected
areas and are found predominantly around the leptomeningeal
blood vessels in the
less severe cases.
• Positive reaction: agglutination (or visible clumping) of the
latex particles and slight clearing of the suspension occurs
within 2-10 minutes .
• Negative reaction: the suspension remains homogenous and
slightly milky in appearance.
• Amplification of virus specific DNA or RNA from CSF using PCR
amplification has become the single most effective method for
diagnosing CSF viral infections.
• It is a highly sensitive and specific test since only trace amounts
of the infecting agent's DNA is required.
• It may identify bacteria in
bacterial meningitis and may
assist in distinguishing the
various causes of viral meningitis.
• The sensitivity of CSF cultures for the diagnosis of viral
meningitis is poor in comparison to the detection of bacterial
• Viruses may also be isolated from throat swabs, blood and
• Enterovirus and adenoviruses maybe found in the feces.
• Crucial diagnostic tool
• Serum antibody detection is less useful for viruses with
high prevalence rates in the general population.
• For viruses with low prevalence rates , diagnosis of
acute viral infection can be made by documenting
• Seroconversion between acute phase and convalescent
• The documentation of synthesis of virus specific
antibodies in CSF is more useful than serum serology
• RDTs have been developed for direct testing of CSF specimens
without prior heat or centrifugation.
• The test is based on the principle of vertical flow
• Gold particles and nitrocellulose membranes are coated with
monoclonal antibodies to capture soluble serogroup-specific
polysaccharide antigens in the CSF.
• Appearance of red lines on the dipsticks will indicate whether
one of the four meningococcal serogroups has been detected in
• The upper line on the dipstick is the positive control and should
always be present.
• If the CSF is positive for one of the serogroups, a lower red line
will also be present. The position of that red line indicates the
specific serogroup based on the RDT that was tested.
• A negative result consists of a single upper pink control line only.
• CBC (complete blood count) & DLC (differential leucocyte
• Liver and Renal function tests
• ESR (erythrocyte sedimentation rate)
• C- Reactive protein
• Electrolytes etc
• MRI and CT are not necessary in patients with uncomplicated
• They may be performed in patients with altered
consciousness, seizures etc