Ch. 12 - Infections of CNS

Question 1

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

Answer 1

Neonates - GBS, E. coli

Infants - GBS, Strep pneumo

Kids/adults - Strep pneumo, Neisseria meningitides

Question 2

3 main routes of infectious spread to meninges and CSF

Answer 2

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

Question 3

Why is phagocytosis impaired in CSF?

Answer 3

Has low opsonic activity

Question 4

Major presenting features of meningitis

Answer 4

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

Often preceded by URI

Question 5

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

Answer 5

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

Question 6

CSF features in bacterial meningitis

Answer 6

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

Question 7

Which abx is the mainstay of bacterial meningitis tx?

Answer 7

Ceftriaxone; add a penicillin as needed for appropriate coverage

Question 8

Major complications of bacterial meningitis

Answer 8

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

Question 9

Where do brain abscesses arising by hematogenous dissemination frequently develop?

Answer 9

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)

Question 10

What is the most common pathogen isolated from brain abscesses?

Answer 10

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

Question 11

CT appearance of brain abscess

Answer 11

Contrast-enhancing ‘ring’ lesion

Question 12

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

Answer 12

MRI

Question 13

When should surgical excision of brain abscesses be considered?

Answer 13

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

Question 14

What abx should you use for postoperative brain abscess?

Answer 14

Vancomycin

Question 15

Clinical features of epidural brain abscess?

Answer 15

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

Question 16

Pott’s puffy tumor

Answer 16

Localized pitting edema of scalp over area affected by epidural abscess

Question 17

Classic presentation of subdural abscess

Answer 17

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

Question 18

What will CSF show in TB meningitis?

Answer 18

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

Question 19

Definitive diagnosis of TB meningitis

Answer 19

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

Question 20

Tx of TB meningitis

Answer 20

Isoniazid, rifampin, ethambutol, pyrazinamide

Question 21

How does intracranial tuberculoma present?

Answer 21

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

Question 22

How does cerebral cryptococcosis present?

Answer 22

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

Question 23

Dx of Cryptococcus

Answer 23

Cryptococcus seen on India ink prep

Positive latex cryptococcal agglutination test

Question 24

Cryptococcus tx

Answer 24

Amphotericin B, 5-fluocytosine, or fluconazole

Question 25

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

Answer 25

Spilled contents can induce anaphylactic shock

Question 26

Medical tx of hydatid cyst

Answer 26

Albendazole

Question 27

How is cerebral toxoplasmosis treated?

Answer 27

Sulfadiazine and pyrimethamine

Question 28

Common cerebral infections in AIDS?

Answer 28

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

Question 29

Most common parasitic dx of CNS

Answer 29

Neurocysticercosis caused by Taenia solium (tapeworm)

Question 30

CSF appearance in neurocysticercosis

Answer 30

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

Question 31

Tx of neurocysticercosis

Answer 31

Surgical intervention + albendazole or praziquantel

Question 32

Presentation and causative organism of herpes simplex encephalitis

Answer 32

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

Question 33

EEG in herpes simplex encephalitis

Answer 33

Focal slowing, periodic spikes or sharp and wave patterns

Question 34

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

Answer 34

Signal changes within temporal lobe with edema and hemorrhage

CSF with mononuclear cells and viral DNA

Question 35

Herpes simplex encephalitis tx

Answer 35

Acyclovir

Question 36

Identify the lesion

Answer 36

Ring-enhancing cerebral abscess with surrounding edema

Question 37

Identify the lesion

Answer 37

Herpes simplex encephalitis in right temporal lobe