1. Acute bacterial meningitis is commonly caused by hematogenous spread of bacteria from other sites of infection to the meninges. Common causative organisms vary by age. 2. Clinical manifestations range from sudden onset of shock and coma to more gradual onset of fever and nonspecific CNS symptoms. Signs include meningeal irritation and increased intracranial pressure. Lumbar puncture reveals pleocytosis and abnormal CSF parameters. 3. Encephalitis is caused by a variety of viruses transmitted by arthropods or direct person-to-person spread. It presents with abrupt fever and neurological deficits that can include seizures or coma. Diagnosis involves CSF analysis and serology. Outcomes range from

1. CNS INFECTIONS

2. 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.

3. 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.

4. Signs of meningeal irritation:
• Nuchal rigidity and back pain
• Kernig’s 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.

7. 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 (<50% of S. glucose)
5- Physical appearance:Turbid with elevated pressure (100-300
mm H2O).
Normal CSF shows: Normal pressure (50-80 mm H2O),
leucocytes (<5/mm3), proteins (20-45 mg/dl) and glucose
(75% of the level of serum glucose).

8. COMPLICATIONS
• Deafness
• Hydrocephalus
• Brain abscess
• Subdural effusion
• Motor disabilities

9. 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 β- 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.

10. 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.

11. 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).

12. 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

14. 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; (Meningoencephalitis).
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.

15. 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 Simplex;and varicella-zoster
infections, Acyclovir is used.