1. Encephalitis & Intracranial Abscesses
Assistant Prof./ Tamer Ata
M.D., Ph.D.
MEDICAL MICRIBIOLIOGY AND IMMUNOLOGY
FACULTY OF MEDICINE
AL-MAAREFA COLLEGES

2. Encephalitis
Definition: is inflammation of the parenchyma of the brain, due direct viral invasion.
Epidemiological pattern:
Epidemic (eg, due to arbovirus, echovirus, coxsackie virus, or poliovirus)
Sporadic (eg, due to herpes simplex, rabies, varicella- zoster, or mumps virus)

3. Encephalitis DNA viruses RNA viruses Herpes viruses HSV1&2 VZV CMV
Causes:
DNA viruses
RNA viruses
Herpes viruses
HSV1&2
VZV
CMV
Polyoma viruses
JC virus
Picorna viruses (enteroviruses)
*polioviruses
*coxsackie viruses
* ECHO viruses
ArBo viruses
Rhabdoviruses (rabies virus)
Reteroviruses (HIV)
Influenza viruses
Measles virus

4. Encephalitis Mode of infection:
Droplet and contact (measles , JC, Herpes, influenza),
Ingestion (enteroviruses),
Insect bites (arthropod-borne viruses),
Animal bites (rabies).
NB: viruses reach the CNS via the
Bloodstream (most viruses ).
Some viruses as herpes simplex virus (HSV), varicella-zoster virus (VZV), and rabies may also travel to the CNS along nerves.
Clinically: fever, headache, confusion, coma, convulsions, paralysis, focal neurological deficit.

5. Herpes simplex virus
the most common cause of viral encephalitis (20-30%)
cause 70% mortality in untreated cases
Mortality decreased with using acyclovir antiviral treatment
HSV1 in immunocompromised person → viremia → CNS also can extend from nerves to CNS causing encephalitis (focal temporal lesion)
HSV2 in females with genital herpes at labor → neonatal herpes→ neonatal encephalitis

7. HSV 1
1ry infection
Latency
Reactivation
Recurrence
Gengivostomatitis: vesicle in mouth cavity, sore throat
Conjunctivitis
Herpeticwhitlow
Viremia in immune-compromised patients → encephalaitis & hepatitis
Ascend along trigeminal nerve to enter trigeminal nerve ganglion
Stress as
-Common cold
-Prolonged sun exposure
-menses
Keratitis
Cold sore → vesicles with crust at angle of mouth and nose
HSV2: genital herpes (vesicles at external genitalia) and latent in sacral root ganglion

8. Varicella-Zoster virus:
Varicella (chicken pox = fever and pleomorphic skin rash which start in trunk) in immunocompromised children may complicated with viremia and encephalitis
Latent in sacral root ganglion → with decreased cell mediated immunity (aging) → zoster (painful vesicles along intercostal nerve)
Also aspirin (NSAID) therapy of chicken pox could cause Reye syndrome (fatty liver & brain swelling and encephalopathy)

9. CMV Influenza virus latent in monocyte/macrophage
In HIV and transplantation immune-compromised patients → reach CNS → retinitis and encephalitis
In pregnancy → congenital infection → fetal microcephaly and mental retardation
Influenza virus
in immunocompromised children may complicated with viremia and encephalitis
Also aspirin (NSAID) therapy influenza in children could cause Reye syndrome

10. Ar.Bo. Viruses Family Virus Vector Flavi-viruses St Louis Encephalitis
Birds → mosquito
West Nile fever
Toga-viruses
Eastern Equine Encephalitis (EEE)
WWE
VEE
Horses → mosquito
Bunya-viruses
La Cross Encephalitis
Mosquito
California Encephalitis

11. Rhabdo-viruses → Rabies virus
Zoonotic in saliva of raped canine animals as dogs → bite → human
Multiply in muscles and peripheral nerves → ascend along nerves to spinal cord (dorsal tract) → ascend to basal ganglia (2nd replication and damage to their nuclei)
Flue like symptoms, insomnia, irritability, hydrophobia, hallucination, coma and death.
Treatment: human rabies Ig &killed rabies vaccine (HDCV→ 5 doses SC)

13. Diagnosis of encephalitis
1. CSF analysis: similar with viral meningitis
- ↑ RBCs in herpes viruses
- PCR : detect viral nucleic acid in CSF
- culture: isolate the virus on suitable cell line
2. Biopsy guided by CT:
Multinucleated giant cell with intranuclear inclusions → HSV and VZV
Foci of swollen cells with intranuclear olw’eye → CMV
intracytoplasmic Negri bodies → rabies
3. Serological: detect specific IgM in patient’s serum

14. Multinucleated giant cell with intranuclear inclusions → HSV and VZV
Foci of swollen cells with intranuclear olw’eye → CMV
intracytoplasmic Negri
bodies → rabies

15. Slow CNS infections
JC virus → infect oligodendrocyte in HIV & transplant patients → demyelination → progressive multifocal leukoencephalopathy
Reteroviruses → HIV: in late stage reach CNS through monocyte → progressive demyelination → progressive multifocal leukoencephalopathy → dementia, memory loss
Measles → late complication in which a defective measles virus persist in CNS → chronic degeneration → subacute sclerosing pan-enecephalitis.
Prions: infective protein which transmitted from cows, sheeps and goats to human through ingestion of infected brain →sub acute spongiform encephalopathy (CreutzFeldt-Jakob disease or made cow disease)

16. Guillain-Barre syndrome
Acute inflammatory demyelinating poly-encephalopathy with ascending paralysis and muscle weakness
Occur post infections with
Cambylobacter (gastroenteritis)
Influenza virus (resp. tract infection)
Zika virus (systemic febrile illness)

17. Extradural or epidural abscess
Intracranial abscess
Rare serious life threatening infections
Include:
Brain abscess
Subdural empyema
Extradural or epidural abscess
Collection of pus intra cerebral
Collection of pus between dura mater and arachnoid matter
Collection of pus between dura mater and the skull.

18. Epidemiology Source or rout of infections
Direct extension from cranial infections (commonest 50%) as sinusitis, mastoiditis, otitis media, mental infection
2. hematogenous (25%) e.g. endocarditis, IV drug abuser, immunocompromised patients
Trauma (10%) as penetrating wound or neurosurgery
Unknown

19. Epidemiology Causative agent
Bacterial (usually mixed aerobic and anaerobic)
- the most common is Streptococci and bacteroides
Fungal as Cryptococcus, candida, aspergillus in immunocompromised
Protozoal as toxoplasma in immunocompromised
Aerobic
anaerobic
Staph. spp. (common in trauma)
Strept. Spp. (dental & otitis media)
Enterobactericiaeia as E. coli (chronic ear infection )
Bacteroides
Anaeronic strept.

20. Clinically: fever, headache, focal neurological deficit, ↑ ICT
Investigation:
CT or MRI
Aspiration guided by CT: culture and sensitivity (aerobic and anaerobic) → proper specific antibiotic
NB: lumbar puncture and CSF is contraindicated (WHY)
Treatment:
surgical drainage under umbrella of empirical antibiotic as ceftriaxone, metronidazole, vancomycin
Shift antibiotic therapy according to results of antibiotic and senility results

21. THANKS