39. Infectious diseases of the CNS

Into which categories can we divide the CNS infections?

- Extra-axial inflammations = meningitis

- Parenchymal inflammations

- Focal suppurating inflammations

- Prion diseases

What is meningitis?

Inflammation of the meninges of the brain or spinal cord

- most commonly bacterial or viral in origin

What are the classical triad of symptoms in meningitis?

- Fever

- Headache

- Neck stiffness

Acute vs. chronic meningitis?

- Acute can both be bacterial or viral

- Chronic is most commonly due to tuberculosis or spirochetes

Acute bacterial meningitis is caused by?

Can be caused by many different bacteria, but the typical organisms depend on the patient age

Which bacteria causes meningitis in infants?

- E.coli

- Group B streptococci

Pathogen causing meningitis in adults?

Neisseria meningitidis

Pathogens causing meningitis in either patients of old age and immunocompromised patients?

- Listeria monocytogenes

- Streptococcus pneumoniae

CSF in bacterial meningitis?

- Neutrophils

- Elevated protein

- Reduced glucose levels

Can the meningitis spread?

May spread to the surface of the brain, causing cerebritis (= inflammation of the surface of the brain)

What can cerebritis cause?

May lead to cerebral abscess

Acute viral meningitis is also called?

Aseptic meningitis

CSF in viral meningitis?

- Lymphocytosis

- Normal protein

- Normal glucose

Which viruses cause viral meningitis?

Virtually any virus can cause viral meningitis

- enteroviruses and HSV are most common

Causes of chronic meningitis?

- Mycobacterium tuberculosis

- Spirochete bacteria

Subtypes of chronic meningitis?

- Tuberculosis meningitis

- Meningovascular syphilis

- Neuroborreliosis

Tuberculosis meningitis often affect?

Often affect the base of the brain

- may affect cranial nerves and pituitary gland

- may cause communicating hydrocephalus

Meningovascular syphilis?

Occur as a part of neurosyphilis

- tertiary phase of syphilis

Neuroborreliosis?

Potential complication of Lyme disease

Parenchymal inflammation is also called?

Encephalitis

Encephalitis is often?

Viral

What is meningoencephalitis?

Inflammation of the brain and meninges

- often simultaneous inflammation

How is the CSF in viral encephalitis?

- Lymphocytosis

- Normal protein

- Normal glucose

Most important forms of viral meningoencephalitis?

- HSV

- Varicella-zoster

- EBV

- Polio

- Rabies

- HIV

- Progressive multifocal leukoencephalitis

- Subacute sclerosing panencephalitis

HSV encephalitis?

Most common cause of fatal sporadic encephalitis

Varicella-zoster encephalitis?

May occur as a side-effect of shingles in immuno-suppressed patients

CMV encephalitis?

May occur in utero as part of TORCH or in immuneo-suppressed patients

Rabies encephalitis?

Rabies virus enters the CNS by ascending along peripheral nerves, from the wound site

What is progressive multifocal leukoencephalopathy?

Condition where immuno-suppressed people (especially those suffering from AIDS), experience reactivation of the JC virus

What is subacute sclerosing panencephalitis?

Progressive brain inflammation in children with persistent measles virus

Parasitic encephalitis may be caused by?

- Teania solium

- Naegleria

- Toxoplasma gondii

Fungal encephalitis may be caused by?

- Aspergillus

- Candida

What are focal infections?

Infections existing in circumscribed areas

- abscess

- empyema

What are the focal infections listed here?

- Epidural abscess

- Cerebral abscess

- Subdural empyema

Epidural abscess?

A collection of pus between dura mater and the bones of the skull or spine

- often occur due to local spreading of an adjacent infection

Subdural empyema?

A collection of pus between the dura and the arachnoid membranes

What can cause subdural empyema?

Most often a complication of sinus infection

- but can also be due to ear infection, cranial trauma or surgery, and bacteremia

Which pathogen is most frequently causing epidural abscess and subdural empyema?

Staphylococcus aureus

Cerebral abscesses are most frequently caused by?

- Bacteroides

- Streptococci or staphylococci aureus

How can the bacterium reach the brain?

- Haematogenous spreading

- Local spreading

Haematogenous spreading? from what

- Acute bacterial endocarditis

- Bronchiectasis

Local spreading? from what

- Mastoiditis

- Paranasal sinusitis

How may cerebral abscesses cause symptoms?

- Local destruction of brain parenchyme

- Increased intracranial pressure

What are prion diseases?

Neurodegenerative disorders caused by prions

What are prions?

Misfolded proteins

- can cause normally-folded proteins to become misfolded upon contact

Pathogenesis of prions disease?

- PrP is a normal membrane protein in nervous cells

- PrPc is its normal conformation, however an abnormal conformation called PrPsc also exist

- PrPsc is resistant to breakdown

- PrPsc clump together and accumulate in the cells, causing injury and apoptosis

What happens to the cortex in prions disease?

Cerebral cortex eventually undergoes spongiform transformation

= become "sponge-like"

What is the mean survival time of prion disease after symptoms occur?

7 months

Why does prions disease occur?

- Spontaneous mutations

- Familiarly due to germ-line mutations

- Ingestion of PrPsc

How can ingestion of PrPsc cause prions disease?

When PrPsc proteins come into contact with PrPs proteins

- the latter will change conformation into PrPsc

Prions diseases in humans?

- Creutzfeldt-Jakob disease

- Variant Creutzfeldt-Jakob disease

- Kuru

What is Creutzfeldt-Jakob disease?

Most common prions disease in humans

- its sporadic in most cases, but familiar and iatrogenic cases exist

What is variant Creutzfeldt-Jakob disease?

A subtype of Creutzfeldt-Jakob, which occurs in persons who eat cattle meat that was infected with prions

What is Kuru?

A prion-based disease prevalent in the people of the fore tribe in Papua New Guinea

- aquired by cannibalism