Cerebral Infect

7/30/2019 Cerebral Infect

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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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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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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.



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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.



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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.



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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

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Cerebral Infect