Brain infective, demyelinating and degenerative diseases

INFECTIVE DISEASES
1. Meningitis
  1. Acute pyogenic meningitis
    1. Bacterial (TB, spirochetal) or fungal disease (cryptococcal); CSF is slightly cloudy with very few cells
  2. Aseptic meningitis
    1. Usually acute viral meningitis; the CSF is clear
  3. Chronic meningitis
    1. Usually bacterial meningitis: in this case the CSF is purulent
  4. Acute meningitis
    1. Most common pathogens
      1. E.Coli
      2. Haemophilus influenzae
      3. Streptococcus pneumoniae
      4. Neisseria meningitidis
    2. Bacterial infections mechanisms:
      1. Hematogenous
        The most frequent
      2. Post-traumatic
      3. Retrograde (from peripheral nerves)
      4. Local extension
    3. Clinical manifestations
      1. Signs of systemic infection
      2. Meningeal irritation and neurological involvement
        Headache
        Photophobia
        Clouding of consciousness
        Neck stiffness
    4. Spinal tap can give us very rapid and useful info
      1. Cloudy or frankly purulent CSF
      2. High number of neutrophils
      3. Increased protein concentration
      4. Reduced glucose content
  5. Bacterial
    1. Tuberculous meningitis
      1. Diagnosis is difficult
        Presentation
        CSF
        Modest pleocytosis with mononuclear and some PMN cells
        High protein concentration
        Glucose is only moderately reduced or normal
        MRI
        Location around the base of the brain and along the ventricular system
      2. Complications
        Hydrocephalus
        Tuberculoma (rare)
      3. Ddx with sarcoidosis
    2. Neurosyphilis
    3. Borrheliosis (Lyme disease)
  6. Mycotic
    1. Aspergillus
      1. It can frequently invade the wall of vessels
      2. It can lead to necrotic abscess
    2. Crytptococcus
      1. Mainly in immunosuppressed patients
  7. Protozoan
    1. Toxoplasma
      1. Common in HIV patients especially before introduction of anti-retroviral therapy
  8. Diagnosis
    1. Physical exam
      1. Photophobia
      2. Brudzinski’s sign
      3. Lasegue straight leg test
      4. Nuchal rigidity
      5. Diffuse myalgia
      6. Vomit
    2. Hemocolture
    3. Lumbar puncture
    4. Hemogas analysis
2. Meningoencephalitis
3. Encephalitis
  1. Viral encephalitis
    1. Mainly a parenchymal infection usually associated with meningeal inflammation
    2. Causes
      1. Coxsackie B
      2. Arbovirus
        Most frequent cause of viral enchepalitis, especially in tropical areas
        West Nile
        Tick born virus (the most frequent in Europe)
      3. Herpes virus
        Relatively common in children and young adults
        Tropism mainly for the temporal region
        Antiviral agents provide effective treatment
      4. CMV
      5. JC virus
        It frequently affects immunosuppressed people (HIV and post-transplant)
      6. HIV
      7. Rabies
        No vaccination
        Retrograde diffusion, it affects mainly motorneurons
4. Damage to brain tissue derives from:
  1. Direct action of infectious agents
  2. Indirect action by secretion of toxins by bacteria
  3. Tissue damage due to inflammatory response and immune mediated mechanisms
5. Brain abscess
  1. Quite rare now
  2. It is a destructive lesion (contrarily to bacterial meningitis)
  3. Ddx both clinically and radiologically is with a tumor
  4. Streptococcus and Staphylococcus are the most commonly isolated organisms
DEGENERATIVE DISEASES
1. Parkinson's disease
  1. Macroscopic aspect
    1. Substantia nigra and locus coeruleus are pale
  2. Microscopic aspect
    1. Catecholaminergic neurons
    2. Reactive glisosis
    3. Lewy bodies
      1. Cytoplasmic eosinophilic inclusions composed of aggregates of alpha-synuclein
  3. Alteration of the nigro-striatal dopaminergic system
2. Alzheimer's disease
  1. Macroscopic aspects
    1. Atrophy of the cerebral cortex, especially in frontal, temporal and parietal areas (not occipital)
    2. Ventricular dilation secondary to atrophy (ex-vacuo)
  2. Microscopic features
    1. Neuritis (senile) plaques
    2. Neurofibrillary tangles
    3. Progressive loss of neurons
    4. Reactive gliosis
3. Huntington's disease
  1. Neuronal degeneration in the striatum complex
  2. Initially patients are hyperkinetic and then evolve in a Parkinson-like state with hypokineasia and rigidity

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Brain infective, demyelinating and degenerative diseases

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