Brain infective, demyelinating and degenerative diseases

Brain infective, demyelinating and degenerative diseases

1. INFECTIVE DISEASES

   • Meningitis
     • Acute pyogenic meningitis
       • Bacterial (TB, spirochetal) or fungal disease (cryptococcal); CSF is slightly cloudy with very few cells
     • Aseptic meningitis
       • Usually acute viral meningitis; the CSF is clear
     • Chronic meningitis
       • Usually bacterial meningitis: in this case the CSF is purulent
     • Acute meningitis
       • Most common pathogens
         • E.Coli
         • Haemophilus influenzae
         • Streptococcus pneumoniae
         • Neisseria meningitidis
       • Bacterial infections mechanisms:
         • Hematogenous
           • The most frequent
         • Post-traumatic
         • Retrograde (from peripheral nerves)
         • Local extension
       • Clinical manifestations
         • Signs of systemic infection
         • Meningeal irritation and neurological involvement
           • Headache
           • Photophobia
           • Clouding of consciousness
           • Neck stiffness
       • Spinal tap can give us very rapid and useful info
         • Cloudy or frankly purulent CSF
         • High number of neutrophils
         • Increased protein concentration
         • Reduced glucose content
     • Bacterial
       • Tuberculous meningitis
         • 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
         • Complications
           • Hydrocephalus
           • Tuberculoma (rare)
         • Ddx with sarcoidosis
       • Neurosyphilis
       • Borrheliosis (Lyme disease)
     • Mycotic
       • Aspergillus
         • It can frequently invade the wall of vessels
         • It can lead to necrotic abscess
       • Crytptococcus
         • Mainly in immunosuppressed patients
     • Protozoan
       • Toxoplasma
         • Common in HIV patients especially before introduction of anti-retroviral therapy
     • Diagnosis
       • Physical exam
         • Photophobia
         • Brudzinski’s sign
         • Lasegue straight leg test
         • Nuchal rigidity
         • Diffuse myalgia
         • Vomit
       • Hemocolture
       • Lumbar puncture
       • Hemogas analysis
   • Meningoencephalitis
   • Encephalitis
     • Viral encephalitis
       • Mainly a parenchymal infection usually associated with meningeal inflammation
       • Causes
         • Coxsackie B
         • Arbovirus
           • Most frequent cause of viral enchepalitis, especially in tropical areas
           • West Nile
           • Tick born virus (the most frequent in Europe)
         • Herpes virus
           • Relatively common in children and young adults
           • Tropism mainly for the temporal region
           • Antiviral agents provide effective treatment
         • CMV
         • JC virus
           • It frequently affects immunosuppressed people (HIV and post-transplant)
         • HIV
         • Rabies
           • No vaccination
           • Retrograde diffusion, it affects mainly motorneurons
   • Damage to brain tissue derives from:
     • Direct action of infectious agents
     • Indirect action by secretion of toxins by bacteria
     • Tissue damage due to inflammatory response and immune mediated mechanisms
   • Brain abscess
     • Quite rare now
     • It is a destructive lesion (contrarily to bacterial meningitis)
     • Ddx both clinically and radiologically is with a tumor
     • Streptococcus and Staphylococcus are the most commonly isolated organisms

2. DEGENERATIVE DISEASES

   • Parkinson's disease
     • Macroscopic aspect
       • Substantia nigra and locus coeruleus are pale
     • Microscopic aspect
       • Catecholaminergic neurons
       • Reactive glisosis
       • Lewy bodies
         • Cytoplasmic eosinophilic inclusions composed of aggregates of alpha-synuclein
     • Alteration of the nigro-striatal dopaminergic system
   • Alzheimer's disease
     • Macroscopic aspects
       • Atrophy of the cerebral cortex, especially in frontal, temporal and parietal areas (not occipital)
       • Ventricular dilation secondary to atrophy (ex-vacuo)
     • Microscopic features
       • Neuritis (senile) plaques
       • Neurofibrillary tangles
       • Progressive loss of neurons
       • Reactive gliosis
   • Huntington's disease
     • Neuronal degeneration in the striatum complex
     • Initially patients are hyperkinetic and then evolve in a Parkinson-like state with hypokineasia and rigidity