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Brain Abscess

Risk Factors & Pathophysiology

Presented byRi

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Definition

A focal, intracerebral infection that beginsas a localized area of cerebritis

->a collection of pus surrounded by awell-vascularized capsule

~Clin Infect Dis. 1997 Oct;25(4):763-79

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Pathophysiology

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The brain is remarkably resistant tobacterial and fungal infection

-> abundant blood supply

-> blood-brain barrier

Animal model: inoculation vs. induced

bacteremia

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Common Sources of Brain Abscess

1. Direct or indirect infection fromparanasal sinuses, middle ear, and teeth(via valveless emissary veins to

cavernous sinus)

2. Penetrating brain injury (low incidence)

3. Metastatic seeding from distantextracranial sources

4. Cryptic (20%~30%) : PFO?

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Clin Microbiol Infect 2003;9;803-809

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Clin Microbiol Infect 2003;9;803-809

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PREDISPOSING FACTORS

IVDA (2.5%)

Congenital heart disease (6.1%) HIV infection (1.2%)

Immunosuppression (3.7%)

Diabetes mellitus (3.1%)

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Stages

1. Early cerebritis stage (D1-3):focal area ofinflammation and edema

2. Late cerebritis stage (D4-9):development of a

necrotic central focus3. Early capsule stage (D10-14):ring-enhancingcapsule of well-vascularized tissue with earlyappearance of peripheral fibrosis

4. Late capsule stage (>D14):host defenses leadto a well-formed capsule

~Clin Infect Dis. 1997 Oct;25(4):763-79

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IMAGING STUDIES

1. Contrasted CT

focal hypodensity->enhances after ivcontrast->ring-enhanced lesion

Frequently located in watershed areas,regular thin-walled capsule withperipheral enhancement

Brain tumor: irregular border & diffuseenhancement

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2. MRI

T1: hypointense with ring-enhancement

T2: hyperintense central area of pussurrounded by a well-defined hypointensecapsule & edema-> surgery

3. Radionuclide scan D/D brain abscess from tumor

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CLINICAL PRESENTATION

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Successful non-surgical treatment ofbrainabscess and necrotizing fasciitis causedby Bacillus cereus.

~Internal Medicine. 41(8):671-3, 2002 Aug.

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Patent Foramen Ovale as aPossible Risk Factor of Brain

Abscess~Neurosurgery. 2001 Jul;49(1):204-6

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Autopsy studies: 20%-35% adults havePFO

Under increased pressure in RA eg.Valsalva maneuver, pulmonaryhypertension->R to L shunt->paradoxicalemboli from v to a

Associated with cryptogenic ischemicstroke (higher prevalence)

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Case Reports

Patient 1

63 y/o male->headache & fever for 5days->CT:hypodense lesion with ring-

enhancement in lt thalamus->B/C(-)->nopulmonary AVF, CHD, endocarditis->TEEwith valsalva maneuver showed PFO->noother distant extracranial lesion exceptpyorrhea alveolaris without focal orofacialinflammatory signs

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Patient 2:

36 y/o man->headache & fever-> no riskfactors->MRI T1:hypointense lesion withring enhancement in lt occipital region-

>TEE: valsalva maneuver revealed PFO->severe periodontitis without any focal

orofacial inflammation

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Conclusion

PFO may be a predisposing factor of brainabscess caused by hematogenous spreadfrom a distant infectious focus

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Thanks for your attention!