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
      • < /ul>

      • 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
Previous articlePhysiology of vision
Next articleComa & Brain stem death
Terri is obsessed with making medical school as painless as possible. She studies and compiles medical school notes in a concise, easy-to-understand format. She also enjoys reading contributions by others. She is an investor in sustainability projects. Her ideal weekend is wine tasting and experimenting on bread-making. She has yet to master the art of Sourdough baking.

LEAVE A REPLY

Please enter your comment!
Please enter your name here