CNS Infections

CNS Infections

Infection of CNS coverings Dura – pachymeningitis Leptomeninges - leptomeningitis

Infections of neural tissue Brain – encephalitis Spinal cord – myelitis

Ventricles - ventriculitis

CNS Infections

Pachymeningitis Sources

Direct spread from chronic suppurative infections of sinuses, ear, mastoid or compound fracture

Manifestations Usually localised +/- overlying

osteomyelitis Extradural abscess Subdural empyaema Spinal epidural abscess.

CNS Infections

Leptomeningitis (commonly purulent) Sources

Haematogenous (most common) Direct from adjacent inflammatory lesion ? Through cribriform plate Iatrogenic eg. spinal tap

Microbiology

CNS Infections

Pathology Gross

Swollen, congested brain (acute inflammation)

Purulent CSF (filling sulci & basal cisterns) Micro

Purulent exudate in subarachnoid space, extending into perivascular spaces

Some cortical oedema +/- degeneration in chronic cases

Brain & Cord:

Purulent meningitis

Brain: Purulent meningitis

Brain: Purulent meningitis

Brain: Purulent meningitis

Brain: Purulent meningitis

Brain: Purulent meningitis

Brain: Purulent meningitis

Spinal cord:

Purulent meningitis

CNS Infections

Acute lymphocytic meningitis Causes

Viruses: ECHO, Coxsackie, Herpes simples II, E-B virus.

Manifestations Similar to bacterial meningitis – less severe Gross: acute inflammation, clear CSF Micro: lymphocytic cellular exudate in CSF

and subarachnoid space

CNS Infections

Chronic meningitis Causes

Mycobacterium tuberculosis - TB Treponema pallidum – syphilis Brucella – brucellosis Fungi – Candida, Cryptococcus, Histopasma Protozoa – Toxoplasma, Amoebae

Micro: Largely mononuclear inflammation with

granulomas

Brain:

Tuberculous meningitis.

Brain: Tuberculous meningitis

Tuberculous meningitis

CNS Infection

Chronic meningitis Complications

Obstructive hydrocephalus Focal infarctions/microinfarcts due to

endarteritis oblitrerans Formation of intracranial mass Cranial nerve palsies

CNS Infections

Infections associated with formation of intracranial mass Tuberculosis – tuberculoma Syphilis – gumma Amoebiasis – amoeboma Aspergillosis – aspergilloma, Crryptococcosis - toruloma. Parasites – cysticercosis, hydatid cyst.

Tuberculoma

Brain: Toruloma

CNS Infections

CNS syphilis (tertiary) Meningoencephalitis

(meningovascular syphilis) Gumma General paresis of the insane (GPI) –

focal infarcts, atrophy and dementia Tabes dorsalis.

CNS syphilis

Brain: Syphilis

CNS Infections

Cerebral abscess Sources

Direct spread (sinusitis, mastoiditis) Haematogenous.

Manifestations Mass effect Complications: spread into ventricles or

subarachnoid space – ventriculitis or meningitis

CNS Infections

Cerebral abscess Pathology

Localised suppuration Surrounding pyogenic membrane Surrounding brain:

Oedema – vasogenic Inflammatory infiltrate rich in plasma cells and

lymphocytes. Gliosis – astrocytes mainly.

CNS: Abscess

Cerebral abscess

Cerebral abscess

Brain: cerebellar abscess.

Encephalitis

Primary encephalitis Acute/subacute viral infections Persistent viral infections Slow viral infections

Secondary encephalitisPost-infectious encephalomyelitis

CNS Infections

Primary viral encephalitisHerpesviruses – HSV 1 and 2Enteroviruses – PoliovirusArbovirusesRabiesvirusPersistent virus infections (SSPE,

PMLE)HIV-1 infection

Encephalitis

Primary encephalitis – morphology Gross

Focal/generalised inflammation +/- necrosis Micro

Mononuclear inflammatory infiltrate with perivascular extension (lyphocytes, plasma cells)

Neuronal destruction + neuronophagia Proliferation of microglia – rod cells Reactive gliosis – astrocytosis Inclusion bodies Demyelination.

Viral encephalitis: Preferred sites for various viruses

Brain: Encephalitis

Viral encephalitis: Histological lesions

Viral encephalitis: Neuronophagia

Encephalitis: Perivascular infiltrate

Encephalitis: Types of inclusion bodies

CNS infection:

Rabies

Brain: Herpes simplex encephalitis

Brain: Herpes encephalitis: vessel necrosis + inflam. cells

Encephalitis: Intranuclear inclusions

CNS: Poliomyelitis

Encephalitis

Primary encephalitis Persistent viral encephalitis

Subacute sclerosing panencephalitis (SSPE) Chronic infection Result of measles virus infection Affects older children Brain shows loss of myelin + gliosis + perivascular

lymphocytic infiltration CSF contains high titres of measles antibody and

viral antigen Expression of aberrant T-cell response to presence

of virus in brain.

Encephalitis

Primary encephalitis Slow virus infections

Progressive multifocal leucoencephalopathy (PMLE)

Infection by papovavirus group (JC virus) In immunosuppressed patients (HD,

chemotherapy for malignancies) Focal demyelination in white matter, basal

ganglia Gitter cells in affected areas + atypical

astrocytes + abnormal oligodendrocytes (contain virions as inclusions)

Brain: Progressive multifocal leukoencephalopathy

Encephalitis

Secondary encephalitis Bacterial eg Brucella Spirochaetal eg Treponema Rickettsial eg. Borrelia Parasitic

Protozoa – Toxoplasma, Plasmodium, Trypanosoma

Metazoa – Schistosoma, Cysticercus, Hydatid.

Viral eg Mumps, Yellow fever

Encephalitis

Postinfectious encephalomyelitisMeaslesRubellaVaricella-ZosterVacciniaInfluenzaVariola.

CNS Changes in HIV Infection

Aseptic meningitis 1-2 weeks after seroconversion in 10%. HIV

1 antibodies in CSF.

Meningoencephalitis Gross

Diffuse cortical atrophy Micro

Chronic inflammation, focal necrosis + gliosis, endarteritis, microglial nodules +/- giant cells, multifocal/diffuse demyelination + gliosis

CNS Changes in HIV Infection

Vacuolar myelopathy (20-30%) Similar to subacute combined

degeneration Immunosuppression (not due to HIV)

Inflammatory myopathy Muscle fibre necrosis + phagocytosis Interstitial infiltration with HIV-

positive macrophages

CNS Changes in HIV Infection

Cranial and peripheral neuropathies Acute & chronic demyelinating

polyneuropathy Distal symmetrical polyneuropathy Polyradiculopathy Mononeuritis multiplex Sensory neuropathy due to

ganglioneuritis (rare)

CNS in Childhood AIDS

Neurological manifestations in 1 year: Microcephaly + mental retardation + delay of

motor development

Micro: Calcification in basal ganglia or deep cortical

white matter (blood vessels) Foci of tissue destruction in grey/white matter Loss or delay in myelination Opportunistic CNS infections (rare in children)