Intracranial infections

Pyogenic meningitis (bacterial)

Location

  • brain stem
  • cerebellum
  • dorsum of brain

Aetiological agents

  • Neisseria meningitis
  • Strep pneumoniae
    • extremes of age
  • Anaerobic/microaerophilic streptococci
    • brain/epidural abscess
    • trauma
    • neurosurgery
  • Group B streptococci
    • neonates/infants
  • Staph epidermitis
    • intracranial shunts
  • Staph aureus
    • post operative surgery
  • Bordetella pertusis
    • children
  • Haemophilus influenzae
    • children
  • E. Coli
    • trauma
    • surgery
    • lumbar puncture
  • Listeria monocytogenes
    • extremes of age
    • immunosuppression

Pathogenesis

  • inflammation
  • acculumation of pus in subarachnoid space
    • interference with CSF flow
    • may result in obstructive hydrocephalus

Factors that may bring about meningeal infection

  • inhabitants of the nasopharynx
  • factors which predispose to blood stream invasion
  • disruption of blood-CSF barrier
  • Low immunoglobulin & complement levels in CSF
  • Organisms with special predilection for the meninges

Clinical presentation

  • Pertaining to meningeal irritation
  • Systemic effects specific for infecting bacteria

Lab investigations

  • Cerebrospinal fluid
    • Macroscopic
      • CSF pressure increased
      • Turbid (cloudy) appearance
    • Biochemical
      • Protein raised
      • Glucose decreased
    • Microscopic
      • Polymorph neutrophils
      • leukocytes increased
        • indicating infection
      • Gram stain
        • for causal bacteria
    • Detection of bacterial antigens
      • RIA
      • ELISA
      • Latex agglutination
  • Xray
    • Chest
    • skull/sinuses

Complications

  • Cranial nerve palsy
    • CN affected: 3, 6, 7, 8
    • transient
  • Persistent deafness
    • unilateral/bilateral
  • Cerebral infarction
    • physical/mental retardation
    • epilepsy
  • Persistent coma
  • Obstructive hydrocephalus
    • accumulation of pus in the subarachnoid space
    • interference with CSF flow

Treatment

  • Medical emergency
    • Rapid clearance of organisms
      • Crucial for survival
  • Choice of drugs
    • Bactericidal drugs active in CSF
    • Gram stain as a guide
    • Evidence based

Prevention

  • Vaccination

_____________________________________________________________________

Types of intracranial infections

  • Tuberculous meningitis
  • Leptospiral meningitis
  • Subdural empyema
  • Brain abscess

Tuberculous meningitis

  • Causal organism
    • Mycobacterium tuberculosis
  • Pathogenesis
    • variable onset & clinical presentation
  • Transmission
    • from elsewhere
    • associated with miliary tuberculosis
  • Lab investigation
    • CSF
      • protein raised
      • glucose decreased/normal
      • moderate pleocytosis
      • mononuclear cells
    • Microscopic
      • Ziehl-Neelsen stain of CSF smear
        • Acid fast bacilli
    • CSF culture
      • Culture on Lowenstein-Jensen medium
        • revealed typical dry, heaped-up yellow to buff-colored colonies of Mycobacterium tuberculosis
      • incubate for 10 days – 6 weeks
  • Treatment
    • symptomatic
    • Anti-tuberculous therapy (MDT)
  • Prevention
    • TB control programme
    • Vaccination
      • BCG (very effective)

Leptospiral meningitis

  • Causal organism
    • Leptospira
  • Pathogenesis
    • Enter skin/mucous membrane
    • Bacteraemia
      • Liver
      • Kidney
      • CNS
      • Lungs
  • Clinical features
    • Liver – jaundice
    • Kidney – Uraemia
    • CNS – Meningitis
    • Lungs – Pneumonia
  • Transmission
    • Zoonosis
      • excreted in urine
      • contaminate water/food
      • entry into man
        • swimming
        • consumption
  • Diagnosis
    • History
    • Clinical features
    • Serum agglutinin antibody
    • Isoloation of leptospirae from
      • blood culture
      • urine culture
  • Treatment
    • Penicillin G
  • Prevention
    • Avoid contact with contaminated environment
    • Post exposure prophylaxis
      • Doxycycline

Darkfield microscopy of leptospiral microscopic a...
Darkfield microscopy of leptospiral microscopic agglutination test

Subdural empyema

  • Causal organism (Polymicrobial)
    • Streptococci
      • Aerobic
      • Microaerophilic/anaerobic
    • Staphylococci
    • Gram –ve enteric bacilli
  • Pathogenesis
    • Access
      • infection from frontal/ethmoid sinuses
      • brain abscess
      • septicaemia
      • post-surgical
    • Pathology
      • Collection of subdural pus
      • Ischaemic necrossi of affected cerebral cortex
  • Clinical features
    • Seizures

Brain abscess

  • Causal organism (polymicrobial)
    • Streptococcus pyogenes
      • Microaerophilic/anaerobic streptococci
    • Staphylococcus aureus
    • Enteric Gram –ve bacilli
    • Pneumococci & meningococci
      • rare
  • Pathogenesis
    • focal intracranial suppuration
  • Spread
    • Blood borne from local foci
      • paranasal sinus infections
        • localisation at frontal lobe
      • middle ear/mastoid infections
        • temporal lobe
        • cerebellum
    • Trauma
      • penetrating wounds
      • postoperative infections
    • Metastatic infections
      • lung infections
      • bone/dental infections
      • endocarditis
      • septicaemia
  • Encapsulation of liquefied brain & pus by fibroblasts
  • Diagnosis
    • Primary focus of infection
    • Clinical findings
    • Imaging studies
      • CT
      • MRI
      • Xray
    • EEG
    • CSF

_____________________________________________________________________

Neurosyphilis

  • Causal organism
    • Treponema pallidum
      • tertiery syphilis
      • 10% of untreated infections
  • Clinical presentation/Types
    • Meningovascular neurosyphilis
    • Paretic neurosyphilis
    • Tabes dorsalis
    • Combination
  • Diagnosis
    • Clinical grounds
    • Past history of syphilis
  • Lab investigations
    • Nonspecific serological tests
      • VDRL
      • Rapid plasma reagin test (RPR)
    • Specific serological tests
      • Treponema pallidum haemagglutination test (TPHA)
      • Fluorescent treponemal antibody absorption (FTA-Abs)
      • Treponema pallidum immobilisation test
  • Treatment
    • High dose penicillin G
    • Erythromycin
      • if allergic to penicillin
      • for babies

Aseptic (Viral) meningitis

  • Acute meningitis, with bacteriologically sterile cultures (not bacterial)
  • Causal organism (neurotropic viruses)
    • Picornavirus
      • Poliovirus
      • Coxsackievirus
      • Echo virus
    • Mumps virus
    • HIV
    • Herpes virus
      • Herpes simplex virus
      • Varicella-Zoster virus
  • Clinical findings
    • Features pertaining to acute meningitis
    • Features pertaining to the specific viral infection

Poliomyelitis (Infantile paralysis)

  • Viral infection affecting the nervous system
    • temporary/permanent paralysis
    • death
  • Causal organism
    • Poliovirus (type 1, 2, 3)
  • Transmission
    • fecal-oral
    • direct contact
    • contact-infected secretions
      • nose
      • mouth
  • Clinical features
    • Subclinical infection
    • Abortive polio
    • Nonparalytic poliomyelitis
    • Paralytic poliomyelitis
  • Complication
    • Permanent disability/deformity
    • Pneumonia
    • Loss of lung/intestinal function
  • Lab investigation
    • CSF
      • CSF pressure increased
      • Clear/slightly turbid
      • Protein/Glucose normal
      • Slight increase in cells
        • mainly lymphocytes
      • Gram stain –ve
        • not bacterial/fungal
    • Blood
      • specific antibody detection
      • blood leucocyte count
        • usually normal
        • leucopaenia
  • Prevention
    • General measures
      • good sanitation
    • Specific measures
      • Immunisation
      • Preparations
        • Inactivated polio vaccine (IPV)
        • Oral polio vaccine (IPV)
          • may also cause vaccine associated paralytic polio (VAPP)

Viral encephalitis (Meningoencephalitis/Encephalomyelitis)

  • Causal organism
    • Arbovirus
      • JE virus
    • Rabies virus
    • Herpes virus
      • Herpes simplex virus (type 1,2)
      • Varicella-zoster virus
      • Cytomegalovirus
        • most common viral pathogen in AIDs
    • Poliovirus
    • HIV
  • Pathogenesis
    • Primary
      • direct invasion
      • multiplication of virus in brain
    • Secondary
      • secondary to other viral infection
      • post vaccination

Slow virus infections

  • Slow progression, prolonged incubation period
  • Causal organism
    • JC virus
      • Progressive multifocal leucoencephalopathy (PML)
        • fatal demyelinating disease
    • Measles virus
      • Subacute sclerosing panencephalitis (SSPE)

Prion diseases

  • Self-replicating protein
  • Diseases
    • Bovine Spongiform encephalopathy (BSE)
    • Transmissible Spongiform encephalopathy (TSE)
    • Mad Cow diease
    • Kuru
      • associated with cannabalism
    • Creutzfeldt-Jakob disease (CJD)
      • variant CJD (vCJD)
      • Gertstmann-Straussler-Scheinker syndrome (gCJD)
    • Scrapie
  • Lab investigation
    • CSF
      • findings similar to viral meningitis
    • Radiography
      • CT
      • MRI
    • EEG
    • Brain biopsy
      • For HSV encephalitis
        • Electron microscopy
        • Immunofluorescence microscopy
    • PCR
      • For HSV encephalitis
        • replace brain biopsy

Rabies encephalitis

  • Transmission
    • Zoonosis (infects all warm blooded animals)
  • Pathogenesis
    • Entry
      • via skin/mucous membrane
      • inhalation, animal bite, contamination of fresh wound
    • Access
      • CNS via peripheral nerves
    • Spread
      • from cell to cell
  • Clinical features
    • Incubation period
      • 1-4 months
    • Prodromal manifestations
      • hydrophobia
    • CNS manifestations
      • convulsions
    • Death
      • CNS/respiratory failure
  • Diagnosis
    • History
    • Clinical manifestations
    • Lab diagnosis
      • Specimen:
        • saliva
        • brain biopsy
      • Stain & Microscopy
        • Negri body
        • Immunofluorescent stain
        • Seller’s stain
          • intracytoplasmic inclusion within nerve cells
      • Electrom microscopy
        • viral particles
  • Treatment
    • Antirabies serum
      • may/may not be effective
    • Supportive
      • Symptomatic
      • life support mechanisms
  • Prevention
    • Postexposure in non-immune person
      • determine if animal is rabid
      • wound debridement
        • flush with water
        • antiseptics
      • Specific treatment
        • hyperimmune rabies serum
        • rabies vaccine
    • Pre-exposure prophylaxis
      • rabies vaccine

Fungal meningitis

  • Cryptococcus neoformans
    • Cryptococcal meningitis
    • associated with avians (birds)
    • Treatment:
      • amphotericin B (with 5-fluorocytosine)
    • Lab diagnosis
      • Antigen detection in CSF
        • ELISA
        • Latex agglutination test
      • Gram stain & india ink stain of CSF
        • yeast cells with typical morphology
      • Immunofluorecence stain


India Ink stain

  • Histoplasma capsulatum
    • Disseminated infection
      • in immunocompromised person
    • Tranmission
      • inhalation
    • Lab diagnosis
      • Silver stain
    • Treatment
      • amphotericin B

  • Coccidioides immitis
    • Coccidioidomycosis
    • Disseminated infection
      • immunocompromised person
    • Clincal features
      • lung infection
      • meningitis

Protozoal meningoencephalitis
*check parasite atlas

  • Causal organism
    • Naegleria sp.
      • can infect healthy person
      • fresh water – swimming
    • Hartmanella sp.
    • Acanthomoeba sp.
      • infects immunocompromised persons
    • Plasmodium falciparum
    • Toxoplasma gondii
  • Lab diagnosis
    • CSF
      • microscopy for causal agents
  • Treatment
    • no effective treatment
    • high mortality rate
    • Sometimes
      • amphotericin B

Helminthic infections

  • Eosinophilic meningitis
    • Angiostrongylus cantonensis
      • ingestion of infective larvae in snails
      • No treatment
    • Gnathostoma spinegerum
      • ingestion of larvae in undercooked fish/seafood
      • Treatment: Albendazole
  • Others
    • Ecchinococcus granulosis
    • Taenia solium
    • Toxocara cati & canis
  • Pathogenesis
    • Caused by migrating larvae of these nematodes
      • in brain/other tissues
    • Life cycle
      • not continued
      • dead larvae
    • Inflammatory response
      • Increased eosinophils
  • Lab investigation
    • History
    • Clinical grounds
    • CSF
      • Eosinophilia (also in blood)
      • larvae
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About terrichan

What Is Faith? "Now faith is the substance for all things hoped for, the evidence of things not seen" (Hebrews 11:1)
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