Ch. 12 - Infections of CNS Flashcards Preview

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Flashcards in Ch. 12 - Infections of CNS Deck (37):
1

Common organisms causing bacterial meningitis in neonates/infants? Adults?

Neonates - GBS, E. coli

Infants - GBS, Strep pneumo

Kids/adults - Strep pneumo, Neisseria meningitides

2

3 main routes of infectious spread to meninges and CSF

1. Hematogenous

2. Retrograde via infected thrombi from infections adjacent to CNS (sinusitis, otitis, mastoiditis)

3. Direct spread into subarachnoid space from skull or paranasal sinus infections

3

Why is phagocytosis impaired in CSF?

Has low opsonic activity

4

Major presenting features of meningitis

High fever + meningismus (HA, neck stiffness, photophobia, vomiting, AMS)

Often preceded by URI

5

How does meningitis presentation differ in infants, elderly, and immunocompromised?

Neck stiffness and fever are often absent; usually present with irritability, confusion, obtundation

6

CSF features in bacterial meningitis

Cloudy CSF, elevated WBC (esp. PMNs), elevated protein, low glucose, positive Gram stain in over 70%

7

Which abx is the mainstay of bacterial meningitis tx?

Ceftriaxone; add a penicillin as needed for appropriate coverage

8

Major complications of bacterial meningitis

Cerebral edema, seizures, communicating hydrocephalus, subdural effusion (esp. in kids), subdural empyema (rare), brain abscess (rare)

9

Where do brain abscesses arising by hematogenous dissemination frequently develop?

Usually multiple at the junction of white and grey matter; specific region is proportional to blood flow - most occur in distribution of MCA (i.e. parietal lobe)

10

What is the most common pathogen isolated from brain abscesses?

Streptococcus (80%); Staph aureus when infection results from trauma or postoperatively

11

CT appearance of brain abscess

Contrast-enhancing 'ring' lesion

12

What is the most sensitive imaging modality for diagnosing a brain abscess?

MRI

13

When should surgical excision of brain abscesses be considered?

Persistent reaccumulation of pus despite repeated aspirations, in accessible site, well-formed fibrous capsule, cerebellar location

14

What abx should you use for postoperative brain abscess?

Vancomycin

15

Clinical features of epidural brain abscess?

Primarily those of osteomyelitis (acute localizing pain, pitting edema of scalp)

16

Pott's puffy tumor

Localized pitting edema of scalp over area affected by epidural abscess

17

Classic presentation of subdural abscess

Patient with history of acute frontal sinusitis who develops severe headaches and high fever, has rapid neurological deterioration with seizures

18

What will CSF show in TB meningitis?

Lymphocytic pleocytosis, elevated protein, low glucose, low chloride, acid-fast bacilli in 20%

19

Definitive diagnosis of TB meningitis

Culture of M. tuberculosis which can take up to 6 weeks

20

Tx of TB meningitis

Isoniazid, rifampin, ethambutol, pyrazinamide

21

How does intracranial tuberculoma present?

Similar to intracranial tumor (raised ICP, focal neurologic signs, seizures)

Systemic sxs of TB in less than 50%

Preoperative dx is usually appreciated only after recognition of TB foci ELSEWHERE

22

How does cerebral cryptococcosis present?

Patient with underlying condition (AIDS, IV drug use, sarcoidosis) hung out with pigeons

23

Dx of Cryptococcus

Cryptococcus seen on India ink prep

Positive latex cryptococcal agglutination test

24

Cryptococcus tx

Amphotericin B, 5-fluocytosine, or fluconazole

25

Why should great care be taken when excising intracerebral hydatid cysts?

Spilled contents can induce anaphylactic shock

26

Medical tx of hydatid cyst

Albendazole

27

How is cerebral toxoplasmosis treated?

Sulfadiazine and pyrimethamine

28

Common cerebral infections in AIDS?

Toxoplasmosis > Cryptococcus > TB, Candida, HSV, progressive multifocal leukoencephalopathy

29

Most common parasitic dx of CNS

Neurocysticercosis caused by Taenia solium (tapeworm)

30

CSF appearance in neurocysticercosis

Lymphocytosis, eosinophilia, positive complement fixation test, occasionally see cysts

31

Tx of neurocysticercosis

Surgical intervention + albendazole or praziquantel

32

Presentation and causative organism of herpes simplex encephalitis

HSV-1; acute necrotizing encephalitis (meningitis, progressive deteriorating neurologic state, seizures)

33

EEG in herpes simplex encephalitis

Focal slowing, periodic spikes or sharp and wave patterns

34

What is seen on MRI with herpes simplex encephalitis? In CSF?

Signal changes within temporal lobe with edema and hemorrhage

CSF with mononuclear cells and viral DNA

35

Herpes simplex encephalitis tx

Acyclovir

36

Identify the lesion

Q image thumb

Ring-enhancing cerebral abscess with surrounding edema

37

Identify the lesion

Q image thumb

Herpes simplex encephalitis in right temporal lobe