Term
| What are the major types of CNS infections? |
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Definition
Differ by
1) Etiology (Viral vs. Non-viral)
2) Distribution (Meningitis vs. Encephalitis)
3) Host (Immune intact vs. immunosuppressed)
4) Route of entry (Penetrating trauma, hematogenous, iatrogenic, trans-axonal) |
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Term
| What are the major causes/forms of Meningitis? |
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Definition
1) Neonatal (N. meningitis, S. pyogenes, Listeria)
2) Child/Adult (N. meningitis, S. pneumonia, Listeria and H. influenza in poor nations)
3) Tuberculosis Meningitis (Diagnosed by PCR of CSF) has symptoms 2-3 week longer with brain-stem involvement (cranial nerves affected)
4) Syphilis
- Can proceed from meningovascular involvement to low-rade meningitis with multifocal arteritis, and on to Tabes Dorsalis and Neurosyphilis.
- HIV-associated Syphilis presents with visual and hearing loss
5) Lyme disease with rash, meningitis and encephalitis (3rd stage) |
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Term
| What are the major causes/routes of entry of pathogens causing brain abscesses? |
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Definition
- 50% enter frontal lobe directly through sinuses (S. pneumo, H. influenza)
- Others enter Temporal lobe via Mastoiditis (S. pneumo and Pseudomonas)
- 25 % enter hematogenously lodging in Gray-white junction (S. aureus and Strep milerri) |
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Term
| What is the radiological progression of brain abscesses? |
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Definition
1) Ring enhancing mass, disseminating 1-2d later causing Suppurative Encephalitis
2) Over next week, diffuse inflammatory infiltrate localizes with central necrosis
3) Over subsequent week, local lesion becomes encapsulated. |
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Term
| What is the most common fungal infection seen in the CNS and how does it progress? |
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Definition
Aspergillis
- Disseminates in airborne form, infecting lungs and sinuses and then extending into the brain and/or bloodstream
- Look for necrotizing angiitis in brain vessels and tissue, with limited CSF dissemination. |
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Term
| What common non-viral CNS infections are seen in immunocompromised patients? |
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Definition
1) Cryptococcis
- Primary pulmonary infection with CNS spread causing severe meningitis and abscess-likes structures around Virchow Robin space.
- Hidden from immune system by capsule and stained with India Ink
2) Candida albicans
3) Cocciciodomycosis
4) Histoplasmosis
5) Toxoplasma
6) Cistericercosis (developing world parasite) |
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Term
| What acute viral infections are seen in the CNS? |
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Definition
1) Enterovirus (Poliomyelitis), Herpes Simplex, HIV, Mumps (rare) all cause Meningitis (nonspecific fever, head ache, stiff neck and CSF pleocytosis)
2) Rabies Virus spreads trans-synaptically, causing Rabies (Negri bodies within neurons)
3) Toga, Flavi and Bunya viruses
4) Post-infectious encephalomyelitis (demyelinating, autoimmune response to acute viral infection or vaccination) |
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Term
| What Herpes viral infections are seen in the CNS? |
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Definition
Life-long infections that persist by continuous shedding or by the molecular capacity to remain in DNA-only form in individual host cells.
1) Alpha (Simplex I, II and Varicella Zoster) have wide host and latency range
- HSV I spread to CNS in immunocompromised is lethal without Acyclovir and manifests with slowed EEG and localized CSF (PCR also used)
- HSV II is lethal if primary infection is in utero or during parturition
2) Beta (CMV, HHV 6 & 7) are most restricted within secretory glands and lymphoreticular tissue)
- CMV is most common cause of congenital deafness
3) Gamma (EBV and HHV8) are most restricted and commonly show arrested viral replication |
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Term
| What chronic viral infections are seen in the CNS? |
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Definition
1) Progressive multifocal leukoencephalopathy (PML) is a chronic demyelinating disease arising from infection by JC virus (Papova virus)
- Begins in GI and then persists in unknown site
- Selectively infects and lyses Oligodendroglia |
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Term
| What Prion infections are seen in the CNS? |
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Definition
1) Spongioform encephalopathy (CJD) occurring in sporadic, iatrogenic and genetic forms.
- Hard to transfer, but blood transfusion and organ transplantation can carry risk. |
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