BRAIN ABSCESS/EMPYEMA

Question 1

It is a focal, suppurative infection within the brain parenchyma, typically surrounded by a vascularized capsule

Answer 1

Brain abscess

Question 2

Common pathogens causing brain abscesses in immunocompetent individuals

Answer 2

In immunocompetent individuals the most important pathogens are
1. Streptococcus spp. (anaerobic, aerobic, and viridans [40%])
2. Enterobacteriaceae (Proteus spp., Escherichia coli sp., Klebsiella spp. [25%])
3. Anaerobes (e.g., Bacteroides spp., Fusobacterium spp. [30%])
4. Staphylococci (10%).

Question 3

In Latin America and immigrants from Latin America, the most common cause of brain abscess

Answer 3

Taenia solium (neurocysticercosis).

Question 4

This infection remains a major cause of focal CNS mass lesions in India and East Asia.

Answer 4

Mycobacterial infection (Tuberculoma)

Question 5

Brain abscess may develop through what mechanism?

Answer 5

A brain abscess may develop
(1) by DIRECT SPREAD from a contiguous cranial site of infection, such as paranasal sinusitis, otitis media, mastoiditis, or dental infection
(2) following HEAD TRAUMA or a NEUROSURGICAL
procedure
(3) as a result of HEMATOGENOUS SPREAD from a remote site of infection.

Question 6

Common locations of otogenic brain asbcess?

Answer 6

Otogenic abscesses occur predominantly in the TEMPORAL LOBE (55–75%) and CEREBELLUM (20–30%).

Question 7

Abscesses that develop as a result of direct spread of infection from the frontal, ethmoidal, or sphenoidal sinuses and those that occur due to dental infections are usually located in the __________.

Answer 7

FRONTAL LOBE

Question 8

Hematogenous abscesses show a predilection
for what territory??

Answer 8

These abscesses show a predilection
for the territory of the MIDDLE CEREBRAL ARTERY (i.e., posterior frontal or parietal lobes).

*often located at the junction of the gray and white matter and are often poorly encapsulated.
*The microbiology of hematogenous abscesses is dependent on the primary source of infection

Question 9

This stage of brain abscess is characterized by perivascular infiltration of inflammatory cells, which surround a central core of coagulative necrosis. Marked edema surrounds the lesion at this stage.

Answer 9

Early Cerebritis (Day 1-3)

Question 10

In this stage of brain abscess, pus formation leads to enlargement of the necrotic center, which is surrounded at its border by an inflammatory infiltrate of macrophages and fibroblasts. A thin capsule of fibroblasts and reticular fibers gradually develops, and the surrounding area of cerebral edema becomes more distinct than in the previous stage.

Answer 10

Late Cerebritis stage (days 4–9)

Question 11

The third stage of brain abscess formation that
is characterized by the formation of a capsule that is better developed on the cortical than on the ventricular side of the lesion. This stage
correlates with the appearance of a ring-enhancing capsule on neuroimaging studies.

Answer 11

Early Capsule Formation (Day 10-13)

Question 12

This stage is defined by a well-formed necrotic center surrounded by a dense collagenous capsule. The surrounding area of cerebral edema has regressed, but marked gliosis with large numbers of reactive astrocytes
has developed outside the capsule

Answer 12

Late Capsule Formation (Day 14 and beyond)

Question 13

What is the most common symptom in patients with a brain abscess?

Answer 13

the most common symptom in patients with a brain abscess is HEADACHE, occurring in >75% of patients.

*characterized as a constant, dull, aching sensation, either hemicranial or generalized,
and it becomes progressively more severe and refractory to therapy.

Question 14

The diagnostic imaging modality of choice for brain abscesses in the early stage or those located in the posterior fossa?

Answer 14

MRI is better than CT for demonstrating abscesses in the early (cerebritis) stages and is superior to CT for identifying abscesses in the posterior fossa.

*Cerebritis appears on MRI as an area of low signal intensity on T1-weighted images with irregular postgadolinium enhancement and as an area of increased signal intensity on T2-weighted images
*On a contrast-enhanced CT scan, a mature brain abscess appears as a focal area of hypodensity surrounded by ring enhancement with surrounding edema (hypodensity).
*On contrast-enhanced T1-weighted MRI, a mature brain abscess has a capsule that enhances surrounding a hypodense center and surrounded by a hypodense area of edema. On T2-weighted MRI, there is a hyperintense central area of pus surrounded by a well-defined hypointense capsule and a hyperintense surrounding area of edema

Question 15

Empirical therapy of community-acquired brain abscess in an immunocompetent patient typically includes

Answer 15

Third- or fourth generation CEPHALOSPORIN (e.g., cefotaxime, ceftriaxone, or cefepime) and METRONIDAZOLE

Question 16

In patients with penetrating head trauma or recent neurosurgical procedures, treatment should include _____

Answer 16

CEFTAZIDIME as the third generation
cephalosporin to enhance coverage of Pseudomonas spp. and VANCOMYCIN for coverage of staphylococci.

*Meropenem plus vancomycin also provides good coverage in this setting.

Question 17

All patients should receive a minimum of _____ weeks of parenteral antibiotic therapy.

Answer 17

6-8 weeks

*Medical therapy alone is not optimal for the treatment of brain abscesses and should be reserved for patients whose abscesses are
neurosurgically inaccessible, for patients with small (<2–3 cm) or nonencapsulated abscesses (cerebritis), and for patients whose condition is too tenuous to allow the performance of a neurosurgical procedure.

Question 18

TRUE OR FALSE: In addition to surgical drainage and antibiotic therapy, patients should receive prophylactic anticonvulsant therapy because of the high risk (~35%) of focal or generalized seizures

Answer 18

TRUE

*anticonvulsant therapy is continued for at least 3 months after resolution of the abscess, and decisions regarding withdrawal are then based on the EEG
*If the EEG is abnormal, anticonvulsant therapy should be continued.
*If the EEG is normal, anticonvulsant therapy can be slowly withdrawn, with close follow-up and repeat EEG after the medication has been discontinued.

Question 19

TRUE OR FALSE: Corticosteroids should be given routinely to patients with brain abscesses.

Answer 19

FALSE

*Intravenous dexamethasone therapy (10 mg every 6 h) is usually reserved for patients with substantial periabscess edema and associated mass effect and increased ICP

Question 20

When to repeat imaging studies to document resolution of brain abscess?

Answer 20

Serial MRI or CT scans should be obtained on a monthly or twice-monthly basis to document resolution of the abscess

Question 21

It is a collection of pus between the dura and
arachnoid membranes

Answer 21

Subdural empyema

Question 22

The most common predisposing condition to the development of subdural empyema?

Answer 22

Sinusitis is the most common predisposing condition and typically involves the frontal sinuses, either alone or in combination
with the ethmoid and maxillary sinuses

*SDE may also develop as a complication of head trauma or neurosurgery.

Question 23

What is the definitive step in the management of subdural empyema?

Answer 23

Emergent neurosurgical evacuation of
the empyema, either through craniotomy, craniectomy, or burr-hole drainage, is the definitive step in the management of this infection.

Question 24

Parenteral antibiotic therapy should be continued for a minimum of ___ weeks after SDE drainage.

Answer 24

3-4 weeks

*SDE is a medical emergency
*Empirical antimicrobial therapy for community-acquired SDE should include a combination of a third-generation cephalosporin (e.g., cefotaxime or ceftriaxone), vancomycin, and metronidazole.
*Patients with hospital-acquired
SDE may have infections due to Pseudomonas spp. or MRSA and should receive coverage with a carbapenem (e.g., meropenem)
and vancomycin.