Infections of the CNS

Question 1

Explain the difference between meningitis and encephalitis

Answer 1

Meningitis: inflammation of the leptomeninges

Encephalitis: Infection of the brain parenchyma (neurons and glial cells)

Question 2

What is the most common type of meningitis?

Answer 2

Bacterial

Question 3

Who gets fungal meningitis?

Answer 3

Immunocompromised people

Question 4

What type of meningitis is caused by amebic and tuberculous infections?

Answer 4

Granulomatous

Question 5

Describe aseptic meningitis

Answer 5

Viral meningitis- self-limiting and usually benign

Question 6

Name two causes of non-infectious meningitis

Answer 6

1) chemical (usually post-op)

2) cancer

Question 7

Which organisms most often cause meningitis in newborns?

Answer 7

Group B strep

E.Coli

Question 8

Which organisms most often cause meningitis in babies (1 month to 1 year)

Answer 8

Strep pneumoniae
Haemophilus influenzae (although less common now due to immunization)

Question 9

Which organisms most often cause meningitis in young people (1- 16 yrs old)?

Answer 9

Neisseria meningitidis
H. influenzae
Strep. Pneumoniae

Question 10

Which organisms most often cause meningitis in adults (16-50 years old)

Answer 10

Strep pneumoniae

Neisseria Meningitidis

Question 11

Which organisms most often cause meningitis in newborns and the elderly?

Answer 11

Listeria monocytogenes

Pseudomonas aeruginosa

Question 12

How are protein levels of CSF affected by viral meningitis?

Answer 12

slightly high

Question 13

Name 4 major causes of chronic meningitis

Answer 13

Tuberculosis
Fungal
Parasitic
Non-infectious - cancer

..Also technically syphilis and Borreliosis

Question 14

Which infectious agent causes a thick exudate at the base of the brain leading to CN deficits?

Answer 14

TB

Question 15

How are CSF protein levels affected by TB?

Answer 15

Moderately high

Question 16

How are CSF glucose levels affected by TB?

Answer 16

Moderately low

Question 17

Name two ways a fungal infection can lead to secondary vasculitis

Answer 17

1) Vascular invasion –> infarct

2) Mycotic aneurysm –> hemorrhage

Question 18

Name two characteristic findings of a gross dissection of a brain infected with cryptococcus

Answer 18

1) Thickened, pale meninges

2) Clear cystic lesions in the basal ganglia –> “swiss cheese” effect

Question 19

Describe the inflammation of cryptococcus in the brain

Answer 19

focal and limited

Question 20

How do cryptococci appear in virchow-robbins space in the brain?

Answer 20

Clear yeasts with a mucoid capsule

Question 21

What is a mycotic aneurysm?

Answer 21

Aneurysm arising from fungal or bacteria infection of the arterial wall

Question 22

What is the most common cerebral parasite?

Answer 22

Cysticercosis

Question 23

Where is cysticercosis found?

Answer 23

Southwestern states and Mexico

Question 24

What type of parasite is toxoplasma gondii?

Answer 24

Protozoa

Question 25

Which are the TORCH infections?

Answer 25

Toxoplasmosis, Other, Rubella, CMV, Herpes Virus

Question 26

What is the "classic triad" or TORCH infections?

Answer 26

chorioretinitis, hydrocephalus, and intracranial calcifications

Question 27

How can toxoplasmosis be identified?

Answer 27

Serology, Biopsy

Question 28

How does Toxoplasmosis appear on H and E?

Answer 28

Bradyzoites

Question 29

Which virus is the most common cause of viral meningitis?

Answer 29

Enterovirus

Question 30

What are some microscopic changes seen in viral hepatitis?

Answer 30

Lymphocytic meningeal infiltrates/inflammation Scanty perivascular lymphocytic extension along the Virchow-Robins space Microglial clusters Neuronophagia

Question 31

Does encephalitis tend to be diffuse or regional?

Answer 31

Can be either

Question 32

What is the most common cause of encephalitis?

Answer 32

Viral infections

Question 33

Which are the primary WBCs seen in a viral encephalitis?

Answer 33

T-lymphocytes Some PMNs can be present in the acute phase

Question 34

What part of the CNS is attacked by the polio virus

Answer 34

anterior horn cells --> LMN lesion

Question 35

Where is the polio virus recovered from in a patient?

Answer 35

Stool or throat

Question 36

What is the incubation period of rabies?

Answer 36

10 days --> year depending on where the bit was located

Question 37

Which are the characteristic histologic findings of rabies?

Answer 37

Negri bodies (cytoplasmic inclusions) seen in neurons of the brainstem, hippocampus and cerebellum (Purkinje cells)

Question 38

How is herpes encephalitis transmitted?

Answer 38

Saliva

Question 39

Where do latent infections of herpes hang out in the body?

Answer 39

Trigeminal ganglion

Question 40

Which lobes does herpes encephalitis localize to?

Answer 40

Temporal lobes Hemorrhagic necrosis of the temporal lobe suggestive of herpes encephalitis. Usually accompanies brain edema

Question 41

What is the characteristic histologic finding of a herpes (HSV-1) inclusion body?

Answer 41

owl's eye

Question 42

What does the chronic form of a herpes HSV-1 infection look like on gross images?

Answer 42

"Burnt out" herpes encephalitis --> hemorrhagic necrosis which progresses to cavitation and atrophy. in long term survivors, necrosis will progress to cavitation and atrophy

Question 43

What population is affected by CMV?

Answer 43

CMV is one of the TORCH infections (so, neonates) Also commonly affects AIDS patients

Question 44

WHat are common histologic findings in CMV infections?

Answer 44

Large intracytoplasmic and intranuclear inclusion bodies

Question 45

How does the gross appearance of brain appear in someone with a CMV infection?

Answer 45

Moderately dilated ventricles with several foci of calcifications in the periventricular area

Question 46

Which infectious agent is responsible for causing Progressive Multifocal Leukoencephalopathy?

Answer 46

JC virus- genus polyomavirus Usually affects immunocompromised, and reversive the immunocompromised state can clear the infection

Question 47

Name 3 histological findings typical of PML.

Answer 47

1) Loss of myelin (with axonal sparing) 2) Bizzare astrocytes 3) Oligodendroglial inclusion

Question 48

Describe the HIV induced vaculolar myelopathy

Answer 48

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

Question 49

List the timing of the 4 stages of a brain abscess

Answer 49

1) Early cerebritis (days 1-3) 2) Confluent necrosis (day 2-7) 3) Early encapsulation (days 5-14) 4) Late encapsulation (2 weeks +)