Infections of the CNS Flashcards
Explain the difference between meningitis and encephalitis
Meningitis: inflammation of the leptomeninges
Encephalitis: Infection of the brain parenchyma (neurons and glial cells)
What is the most common type of meningitis?
Bacterial
Who gets fungal meningitis?
Immunocompromised people
What type of meningitis is caused by amebic and tuberculous infections?
Granulomatous
Describe aseptic meningitis
Viral meningitis- self-limiting and usually benign
Name two causes of non-infectious meningitis
1) chemical (usually post-op)
2) cancer
Which organisms most often cause meningitis in newborns?
Group B strep
E.Coli
Which organisms most often cause meningitis in babies (1 month to 1 year)
Strep pneumoniae Haemophilus influenzae (although less common now due to immunization)
Which organisms most often cause meningitis in young people (1- 16 yrs old)?
Neisseria meningitidis
H. influenzae
Strep. Pneumoniae
Which organisms most often cause meningitis in adults (16-50 years old)
Strep pneumoniae
Neisseria Meningitidis
Which organisms most often cause meningitis in newborns and the elderly?
Listeria monocytogenes
Pseudomonas aeruginosa
How are protein levels of CSF affected by viral meningitis?
slightly high
Name 4 major causes of chronic meningitis
Tuberculosis
Fungal
Parasitic
Non-infectious - cancer
..Also technically syphilis and Borreliosis
Which infectious agent causes a thick exudate at the base of the brain leading to CN deficits?
TB
How are CSF protein levels affected by TB?
Moderately high
How are CSF glucose levels affected by TB?
Moderately low
Name two ways a fungal infection can lead to secondary vasculitis
1) Vascular invasion –> infarct
2) Mycotic aneurysm –> hemorrhage
Name two characteristic findings of a gross dissection of a brain infected with cryptococcus
1) Thickened, pale meninges
2) Clear cystic lesions in the basal ganglia –> “swiss cheese” effect
Describe the inflammation of cryptococcus in the brain
focal and limited
How do cryptococci appear in virchow-robbins space in the brain?
Clear yeasts with a mucoid capsule
What is a mycotic aneurysm?
Aneurysm arising from fungal or bacteria infection of the arterial wall
What is the most common cerebral parasite?
Cysticercosis
Where is cysticercosis found?
Southwestern states and Mexico
What type of parasite is toxoplasma gondii?
Protozoa
Which are the TORCH infections?
Toxoplasmosis, Other, Rubella, CMV, Herpes Virus
What is the “classic triad” or TORCH infections?
chorioretinitis, hydrocephalus, and intracranial calcifications
How can toxoplasmosis be identified?
Serology, Biopsy
How does Toxoplasmosis appear on H and E?
Bradyzoites
Which virus is the most common cause of viral meningitis?
Enterovirus
What are some microscopic changes seen in viral hepatitis?
Lymphocytic meningeal infiltrates/inflammation
Scanty perivascular lymphocytic extension along the Virchow-Robins space
Microglial clusters
Neuronophagia
Does encephalitis tend to be diffuse or regional?
Can be either
What is the most common cause of encephalitis?
Viral infections
Which are the primary WBCs seen in a viral encephalitis?
T-lymphocytes
Some PMNs can be present in the acute phase
What part of the CNS is attacked by the polio virus
anterior horn cells –> LMN lesion
Where is the polio virus recovered from in a patient?
Stool or throat
What is the incubation period of rabies?
10 days –> year depending on where the bit was located
Which are the characteristic histologic findings of rabies?
Negri bodies (cytoplasmic inclusions) seen in neurons of the brainstem, hippocampus and cerebellum (Purkinje cells)
How is herpes encephalitis transmitted?
Saliva
Where do latent infections of herpes hang out in the body?
Trigeminal ganglion
Which lobes does herpes encephalitis localize to?
Temporal lobes
Hemorrhagic necrosis of the temporal lobe suggestive of herpes encephalitis. Usually accompanies brain edema
What is the characteristic histologic finding of a herpes (HSV-1) inclusion body?
owl’s eye
What does the chronic form of a herpes HSV-1 infection look like on gross images?
“Burnt out” herpes encephalitis –> hemorrhagic necrosis which progresses to cavitation and atrophy. in long term survivors, necrosis will progress to cavitation and atrophy
What population is affected by CMV?
CMV is one of the TORCH infections (so, neonates)
Also commonly affects AIDS patients
WHat are common histologic findings in CMV infections?
Large intracytoplasmic and intranuclear inclusion bodies
How does the gross appearance of brain appear in someone with a CMV infection?
Moderately dilated ventricles with several foci of calcifications in the periventricular area
Which infectious agent is responsible for causing Progressive Multifocal Leukoencephalopathy?
JC virus- genus polyomavirus
Usually affects immunocompromised, and reversive the immunocompromised state can clear the infection
Name 3 histological findings typical of PML.
1) Loss of myelin (with axonal sparing)
2) Bizzare astrocytes
3) Oligodendroglial inclusion
Describe the HIV induced vaculolar myelopathy
Spastic paraparesis with hyperreflexia and ataxia
Vacuolation of spinal cord white matter
Resembles subacute combined degeneration due to B12 deficiency, and viral antigens can not usually be detected
List the timing of the 4 stages of a brain abscess
1) Early cerebritis (days 1-3)
2) Confluent necrosis (day 2-7)
3) Early encapsulation (days 5-14)
4) Late encapsulation (2 weeks +)
