CNS INFECTIONS

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CNS INFECTIONS

• PROF. DR. SHAHENAZ M. HUSSEIN

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OBJECTIVES

• By the end of this lecture you will be able to
  understand the followings
• Etiology, clinical manifestations,
  investigations, and treatment of acute bacterial
  meningitis.
• Etiology, clinical manifestations, laboratory
  findings, diagnosis and management of
  encephalitis.
• Slide and video demonstration of some
  neurological manifestations.

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Acute Bacterial Meningitis

• Etiology
• First 2 months of life Group B Streptococcus,
  gram negative bacilli, S. pneumoniae, Neisseria
  meningitides, Haemophilus influenzae type b. and
  L. monocytogenes.
• Children 2 mo-12yr of age 1- S. pneumoniae
• 2-
  N. meningitides
• Alterations of host defense
• Pseudomonas aeruginosa, Staphylococcus aureus,
  Salmonella spp., and L. monocytogenes.
• Mode of infection Bacterial meningitis most
  commonly results from hematogenous dissemination
  of microorganisms from a distant site of
  infection.

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• Clinical Manifestations The onset of acute
  bacterial meningitis has two predominant
  patterns
• 1- The more dramatic less common presentation is
  sudden onset with rapidly progressive
  manifestations of shock, purpura, DIC,
  unconsciousness, and frequently resulting in
  death within 24 hours.
• 2- More often, meningitis is preceded by several
  days of fever with upper respiratory or GIT
  symptoms followed by nonspecific signs of CNS
  infection such as lethargy or irritability.
• Non specific findings Fever,
  anorexia, poor feeding, myalgia, arthralgia,
  tachycardia, hypotension, and petechiae,or an
  erythematous macular rash.

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• Signs of meningeal irritation
• Nuchal rigidity and back pain
• Kernigs sign flexion of the hip 90 degrees with
  subsequent pain and limitation with extension of
  the leg.
• Brudzinski sign involuntary flexion of the knees
  and hips after passive flexion of the neck while
  the patient in supine position.
• Symptoms and Signs of increased ICP
• 1- Headache, and vomiting
• 2- Bulging fontanel or widening of the sutures
• 3- Cranial nerve neuropathies.
• 4- Hypertension with bradycardia
• 5- Apnea or hyperventilation, stupor and coma.

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• Seizures (focal or generalized) due to,
  cerebritis, infarction or electrolyte
  disturbances. Seizures that occur on presentation
  or within the first 4 days of onset are usually
  of no prognostic significance.
• Diagnosis
• Lumbar puncture for CSF analysis should be
  performed
• 1- Microorganisms on gram stain and culture.
• 2- Neutrophil pleocytosis (300-2000/mm3).
• 3- Elevated protein (100-500mg/dL)
• 4- Reduced glucose concentration (lt50 of S.
  glucose)
• 5- Physical appearanceTurbid with elevated
  pressure (100-300 mm H2O).
• Normal CSF shows Normal pressure (50-80 mm H2O),
  leucocytes (lt5/mm3), proteins (20-45 mg/dl) and
  glucose (75 of the level of serum glucose).

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COMPLICATIONS

• Deafness
• Hydrocephalus
• Brain abscess
• Subdural effusion
• Motor disabilities

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• Treatment 1- Initial Antibiotic
  Therapy
• -Ampicillin 200mg/kg with either cefotaxime or
  ceftriaxone100mg/kg, if gram-ve bacilli present
  give Ampicillin with Gentamycin for neonatal
  meningitis.
• -Vancomycin 60mg/kg/24hr given every 6 hr in
  combination With either cefotaxime (200mg/kg/24hr
  given every 6 hours) or ceftriaxone
  (100mg/kg/24hr once or twice daily) in older
  infants and children.
• -Patients allergic to ß- Lactam antibiotics can
  be treated with chloramphenicol, 100mg/kg/d,
  given every 6 hr. Duration of therapy At
  least for 7-14 days I.V.
• -Corticosteroids I.V dexamethasone 0.15
  mg/kg/dose given every 6hr for 2 days for
  children older than 6wk with acute bacterial
  meningitis caused by H. influenzae type b to
  decrease the permanent auditory nerve damage.

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• 2-Supportive and symptomatic therapy
  A-Good evaluation and monitoring are
  essential.
• B-Correction of dehydration and electrolyte
  disturbances and proper nutrition.
• C-Control of seizures
• D- Management of neurological complications
• Prevention
• - Vaccination and antibiotic prophylaxis for
  susceptible at risk contacts.
• Close contact should be treated with Rifampin
  10mg/kg/dose every 12hr, for 2 days (in N.
  meningitides) and 20mg/kg/day for 4 days in H.
  influenzae type b.

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• ENCEPHALITIS
• Definition Infection involving cerebral
  parenchyma, in some patients the meninges
  involved with the parenchyma causing
  meningoencephalitis.
• Etiology
• 1- Arthropod born virus Arbovirus Flavivirus
  
• -St. Louis encephalitis. Birds (culex
  mosquitoes).West-Nile virus.
• - Western equine encephalitis.Birds (Colisata
  mosquitoes).
• - Eastern equine encephalitis. Birds ( Culisata
  mosquitoes).
• - Venezuelan equine encephalitis. Hoarses ( 10
  species mosquitoes).
• - California encephalitis (Bunya virus).
  Chipmunks (Aedes mosquitoes).
• - Clorado tick fever (Wood tick).

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• Etiology continue
• 2-Herpes simplex virus.
• 3- Varicella or vaccine.
• 4- Measles or vaccine
• 5-Influenza .
• 6- Poliomyelitis.
• 7- Congenital infections Cytomegalovirus,
  Rubella.
• 8-HIV
• 9-Rabies
• 10-Rubella
• 11-E.B.V.
• 12-Mycoplasma pneumonia

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• Clinical manifestations
• - Duration of illness 2-5 days ----------up 3
  weeks.
• Abrupt onset of fever, chills, headache, nausia,
  vomiting.
• Generalized weakness, seizures, coma, ataxia,
  cranial nerve palsies.
• Meningeal signs in some cases (Meningoencephaliti
  s).
• Laboratory findings
• Lymphocytosis in blood picture.
• CSF 100-500 WBCs/ul pleocytosis (lymphocytes).
• Serology Specific antibodies( IgM) in the 1st
  week.
• PCR for viral antigens.
• - Neuroimaging CT or MRI for brain.
• - EEG for temporal lobe lesion of herpes
  simplex.
• - Brain biopsy for undiagnosed cases.

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• Complications
• Acute disseminated encephalomyelitis ADEM
  usually follow measles or varicella diseases or
  vacination.
• Mortality is variable according to the type of
  encephalitis 2-5 in St. Louis and 20 in
  Venezuelan equine. And 50 in Eastern equine.
• Neurological sequelea ranging from 1 to more
  than 50 in Eastern equine encephalitis.
• Therapy
• Supportive except in Herpes Simplexand
  varicella-zoster infections, Acyclovir is used.