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Neurological
Infections
Gerard Gabriel P. Reotutar, RM, RN, MAN
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Encephalitis
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Encephalitis
Encephalitis is an acute inflammation of the brain.
It may be caused by a number of
microorganisms including viruses,
bacteria, and fungi. In the Westernworld, viral encephalitis is the most
common type of the disorder; it is
typically caused by the herpes simplexvirus. Other causes of viral encephalitis
are measles, mumps, polio, rabies, and
influenza.
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Viral Encephalitis
Viral encephalitis can occur either as a
direct effect of an acute infection, or as
one of the sequelae of a latent infection.
The most common causes of acute viralencephalitis are rabies virus, Herpes
simplex, poliovirus, and measles
virus. Other causes include infectionby flaviviruses such as St. Louis
encephalitis virus or West Nile virus, or
by Togaviridae .
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Bacterial Encephalitis
It can be caused by a bacterial infection, such
as bacterial meningitis, spreading directly to
the brain (primary encephalitis), or may be a
complication of a current infectious diseasesyphilis (secondary encephalitis).
Certain parasitic or protozoal infestations,
such as toxoplasmosis, malaria, or primaryamoebic meningoencephalitis, can also
cause encephalitis in people with
compromised immune systems.
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Encephalitis LethargicaIt is an atypical form of encephalitis which caused
an epidemic from 1918 to 1930. Those who survived
sank into a semi-conscious state that lasted for
decades until the Parkinson's drug L-DOPA was used
to revive those still alive in the late 1960s by Oliver
Sacks.
There have been only a small number of isolated
cases in the years since, though in recent years a few
patients have shown very similar symptoms. The
cause is now thought to be either a bacterial agent
or an autoimmune response following infection.
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Limbic System EncephalitisIn a large number of cases, called limbic
encephalitis, the pathogens responsible
for encephalitis attack primarily
the limbic system (a collection ofstructures at the base of the brain
responsible for emotions and many
other basic functions).
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Manifestations and Diagnosis
Adult patients with encephalitis present with:
acute onset of fever,
headache,
confusion, andsometimes seizures.
Younger children or infants may present:
irritability,poor appetite and
fever.
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Manifestations and Diagnosis
Neurological examinations usually reveal a
drowsy or confused patient.
Stiff neck, due to the irritation of themeninges covering the brain, indicates that the
patient has either meningitis or
meningoencephalitis.
Magnetic resonance imaging offers better
resolution.
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Manifestations and Diagnosis
Examination of the cerebrospinal
fluid obtained by a lumbar puncture procedure
usually reveals increased amounts of protein
and white blood cells with normal glucose.
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TreatmentTreatment is usually symptomatic.
Reliably tested specific antiviral agents
are few in number(e.g. acyclovir for herpes simplex virus)
and are used with limited success in
treatment of viral infection, with theexception of herpes simplex encephalitis.
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TreatmentIn patients who are very sick,
supportive treatment, such as
mechanical ventilation, is equally
important.
Corticosteroids
(e.g., methylprednisolone) are used toreduce brain swelling and inflammation.
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TreatmentSedatives may be needed for
irritability or restlessness.
For Mycoplasma infection,parentral tetracycline is given.
Encephalitis due to Toxoplasma istreated by giving a combination
ofpyrimethamine and sulphadimidine.
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Meningitis
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Meningitis
It is inflammation ofthe protective
membranes covering
the brain and spinal cord, known
collectively as the meninges. Meningitiscan be life-threatening because of the
inflammation's proximity to the brain
and spinal cord; therefore the conditionis classified as a medical emergency.
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The classic triad of diagnostic signs consists ofnuchal
rigidity, sudden high fever, and altered mental
status; If none of the three signs is present, meningitis
is extremely unlikely.
Nuchal rigidity (inability to flex the neck forward
passively due to increased neck muscle tone and
stiffness). Nuchal rigidity occurs in 70% of adultcases of bacterial meningitis. Other signs of
meningitis include the presence of positive
Kernig's sign or Brudzinski's sign.
Manifestations and Diagnosis
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Kernig's sign is assessed with the patient
lying supine, with the hip and knee flexed to
90 degrees. In a patient with a positive Kernig's sign,pain limits passive extension of the knee.
A positive Brudzinski's sign occurs when
flexion of the neck causes involuntary flexionof the knee and hip.
Manifestations and Diagnosis
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Manifestations and Diagnosis
Severe headache is the most common symptom ofmeningitis occurring in almost 90% of cases of
bacterial meningitis,
photophobia (intolerance to bright light)
phonophobia (intolerance to loud noises)
Another test, known as the "jolt accentuation
maneuver" helps determine whether meningitis ispresent in patients reporting fever and headache. The
patient is told to rapidly rotate his or her head
horizontally; if this does not make the headache worse,
meningitis is unlikely.
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Blood tests and imaging
The most important test in identifying or ruling out
meningitis is analysis of the cerebrospinal fluid
through lumbar puncture (spinal tap).
However, lumbarpuncture is contraindicated if there is a mass in the
brain (tumor or abscess) or intracranial pressure (ICP) is
elevated, as it may lead to brain herniation. If someone
is at risk for either a mass or raised ICP (recent head
injury, a known immune system problem, localizing
neurological signs, or evidence on examination of a
raised ICP), a CT or MRI scan is recommended prior to
the lumbar puncture.
Manifestations and Diagnosis
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Manifestations and Diagnosis
Lumbar punctureThe "opening pressure" of the CSF is measured using
a manometer. The pressure is normally between
6 and 18 cm water (cmH2O);in bacterial meningitis
the pressure is typically elevated. The initial
appearance of the fluid may prove an indication of
the nature of the infection: cloudy CSF indicates
higher levels of protein, white and red blood cellsand/or bacteria, and therefore may suggest bacterial
meningitis, eosinophils predominate, suggesting
parasitic or fungal etiology.
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Bacterial Meningitis
In premature babies and newborns up to three months old,common causes are group B streptococci(subtypes III which
normally inhabit the vagina and are mainly a cause during the first
week of life). Older children and adults are more commonly
affected by Neisseria meningitidis (meningococcus), and
Streptococcus pneumoniae.The same pathogens are also more common in those
with an impaired immune system. In a small
proportion of people, an infection in the head andneck area, such as otitis media or mastoiditis, can
lead to meningitis. Recipients of cochlear implants for
hearing loss are at an increased risk of pneumococcal
meningitis.
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Bacterial Meningitis
Tuberculous meningitis, meningitis due to
infection with Mycobacterium tuberculosis, is
more common in those from countries
where tuberculosis is common, but is alsoencountered in those with immune problems,
such as AIDS.
The most common cause of recurrent meningitis
is skull fracture.
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Viral Meningitis
Viruses that can cause meningitis
include enteroviruses, herpes simplex virus type 2 (and
less commonly type 1), varicella zoster virus
(known for causing chickenpox and shingles),mumpsvirus, HIV
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Parasitic Meningitis
A parasitic cause is often assumed when there
is a predominance of eosinophils (a type of
white blood cell) in the CSF. The most common
parasites implicated are the
conditions cysticercosis, toxocariasis,
baylisascariasis, paragonimiasis, and a
number of rarer infections andnoninfective conditions
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Aseptic Meningitis
The term aseptic meningitis refers loosely to all
cases of meningitis in which no bacterial
infection. This is usually due to viruses, but it
may be due to bacterial infection that has
already been partially treated, with
disappearance of the bacteria from the
meninges, or by infection in a space adjacent to
the meninges (e.g. sinusitis). Endocarditis(infection of the heart valves with spread of small
clusters of bacteria through the bloodstream)
may cause aseptic meningitis.
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Aseptic Meningitis
It may also result from infection with spirochetes, atype of bacteria that includes Treponema
pallidum(the cause of syphilis) and Borrelia
burgdorferi(known for causing Lyme disease).
Meningitis may be encountered in cerebral
malaria (malaria infecting the brain). Fungal
meningitis, e.g. due to Cryptococcus neoformans,
is typically seen in people with immune deficiencysuch as AIDS. Amoebic meningitis, meningitis due
to infection with amoebae such as Naegleria
fowleri, is contracted from freshwater sources
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Non-Infectious Meningitis
Meningitis may occur as the result of several non-infectious causes: spread of cancer to the meninges
(malignant meningitis)and certain drugs (mainly non-
steroidal anti-inflammatory
drugs, antibiotics and intravenous immunoglobulins).
It may also be caused by several inflammatory
conditions such as sarcoidosis (which is then
called neurosarcoidosis - a disease in which lumps of
fibrous tissue and collections of cells granulomasappear on the skin and internal organs), connective
tissue disorders such as systemic lupus
erythematosus
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TreatmentMeningitis is potentially life-threatening and has a high mortalityrate if untreated;
Treatment with wide-spectrum antibiotics should not be
delayed while confirmatory tests are being conducted.
If meningococcal disease is suspected in primary care,
guidelines recommend that benzylpenicillin be administered
before transfer to hospital.
Intravenous fluids should be administered if
hypotension (low blood pressure) or shock are present,
admission to an intensive care unit if deemed necessary.
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TreatmentAdjuvant treatmentawith corticosteroids (usually dexamethasone)has been shown in some studies to reduce rates of mortality, severe
hearing loss and neurological damage in adolescents and adults
Mechanical ventilation may be needed if the level ofconsciousness is very low, or if there is evidence of respiratory
failure.
If there are signs of raised intracranial pressure,
various treatments to decrease the intracranial
pressure with medication (e.g.mannitol).
Seizures are treated with anticonvulsants.
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TreatmentAntibiotics
Empiric antibiotics (treatment without exact
diagnosis) must be started immediately, even before
the results of the lumbar puncture and CSF analysisare known. The choice of initial treatment
consists ofa third-generation cefalosporin such
as cefotaxime or ceftriaxone. If theres resistance
to cefalosporins is increasingly found in
streptococci, addition ofvancomycin to the
initial treatment is recommended.
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TreatmentViral meningitis typically requires supportive
therapy only; most viruses responsible for
causing meningitis are not amenable to
specific treatment. Herpes simplexvirus and varicella zoster virus may respond to
treatment with antiviral drugs such
as aciclovir, Mild cases of viral meningitis can
be treated at home with conservativemeasures such as fluid, bedrest, and
analgesics
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TreatmentFungal meningitis, such as
cryptococcal meningitis, is
treated with long courses of
highly dosed antifungals, such
as amphotericin B and flucytosine
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Thank You