Microbial Diseases of the Nervous System - In Depth

How Microbes Enter the Nervous System

  • Methods of Entry:
    • Skull or backbone fractures
    • Medical procedures
    • Along peripheral nerves
    • Through blood or lymph

The Nervous System

  • Components:
    • Brain
    • Spinal cord
    • Central nervous system (CNS)
    • Peripheral nervous system (PNS)

Microbial Diseases of the Nervous System

  • Bacterial Meningitis:
    • Characterized by the growth of bacteria in cerebrospinal fluid (CSF) in the subarachnoid space of the CNS.
    • Blood Brain Barrier:
    • Capillaries prevent passage of many substances (e.g., antimicrobial drugs) into the CNS.
    • Definitions:
    • Meningitis: Inflammation of meninges.
    • Encephalitis: Inflammation of the brain.

Bacterial Meningitis Symptoms and Diagnosis

  • Symptoms: Fever, headache, stiff neck, nausea, vomiting.
  • May lead to convulsions and coma.
  • Diagnosis:
    • Gram stain or latex agglutination of CSF.
  • Treatment:
    • Usually treated with cephalosporins.

Common Causes of Bacterial Meningitis

  • Leading Causes:
    • Haemophilus influenzae
    • Streptococcus agalactiae
    • Neisseria meningitidis
    • Listeria monocytogenes
    • Streptococcus pneumoniae
  • Symptoms in Children:
    • Fever, lethargy, irritability, headache, photophobia, and stiff neck.

Specific Bacterial Meningitis Cases

  • Haemophilus influenzae Meningitis:

    • Primarily affects children (6 months to 4 years).
    • Gram-negative bacteria; prevented by Hib vaccine.

  • Meningococcal Meningitis:

    • Caused by Neisseria meningitidis; may lead to shock and death within 24 hours.
    • Transmission: Salivary droplets.

  • Streptococcus pneumoniae Meningitis:

    • Gram-positive; most common in children.
    • Prevented by vaccination.

  • Listeriosis:

    • Caused by Listeria monocytogenes; foodborne disease associated with meningitis.
    • Transmission from contaminated food (e.g., soft cheeses, hot dogs).

  • Tetanus:

    • Caused by Clostridium tetani; results from deep wounds.
    • Prevented by DTP vaccine; treated with tetanus immune globulin.

  • Botulism:

    • Caused by Clostridium botulinum; results from food poisoning.
    • Treatment includes prevention of proper canning.

  • Leprosy (Hansen’s Disease):

    • Caused by Mycobacterium leprae; affects skin and peripheral nerves.
    • Exists in different forms:
    • Tuberculoid leprosy: mild, less severe.
    • Lepromatous leprosy: widespread, more severe.

Viral Diseases of the Nervous System

  • Viral Meningitis:

    • More common than bacterial; milder symptoms; recovery in 7-10 days.
    • Often caused by picornaviruses; transmitted via fecal-oral route.

  • Viral Encephalitis:

    • More severe than viral meningitis; can cause death.
    • Common causes include arboviruses (e.g., West Nile, LaCrosse).

  • Polio:

    • Caused by polioviruses; leads to motor nerve cell destruction and paralysis.
    • Prevention via vaccines!

  • Rabies:

    • Characterized by fatal meningoencephalitis; spread through animal bites.
    • Symptoms develop with identifiable stages including incubation and acute neurological phases.

Other Nervous System Infections

  • Cryptococcal Meningoencephalitis:

    • Fungal disease from inhaling dust containing pigeon droppings.
    • Opportunistic, mainly affecting immunocompromised individuals.

  • Transmissible Spongiform Encephalopathies:

    • Include diseases like Creutzfeldt-Jakob disease and Bovine Spongiform Encephalopathy; transmitted through ingestion or transplants.