abdominal abcess

Differential diagnosis of brain abscess

•Epidural and subdural empyema

•Septic dural sinus thrombosis

•Mycotic cerebral aneurysms

•Septic cerebral emboli with associated infarction

•Acute focal necrotizing encephalitis (most commonly due to

herpes simplex virus)

•Metastatic or primary brain tumors

•Pyogenic meningitis

Brain abscess

Direct spread

Post neurosurgery

Dental infection

Frontal or ethmoid sinuses

otitis media and mastoiditis

Bullet wounds

Brain abscess

Hematogenous spread

Intraabdominal infection

Chronic pulmonary infections

Skin infections

Pelvic infection

Esophageal dilation and endoscopic sclerosis of

esophageal varices

Cyanotic congenital

heart diseases

Bacterial endocarditis

Microbiologic pathogens in brain abscesses, according to major primary

source of infection

Source of infection Pathogens

Paranasal sinuses

Streptococcus (especially Streptococcus

milleri), haemophilus, bacteroides,

fusobacterium

Odontogenic sources Streptococcus, bacteroides, prevotella,

fusobacterium, haemophilus

Otogenic sourcesEnterobacteriaceae, streptococcus,

pseudomonas, bacteroides

LungsStreptococcus, fusobacterium,

actinomyces

Urinary tract Pseudomonas, enterobacter

Penetrating head traumaStaphylococcus aureus, enterobacter,

clostridium

Neurosurgical procedureStaphylococcus, streptococcus,

pseudomonas, enterobacter

Endocarditis Viridans streptococcus, S. aureus

Congenital cardiac malformations

(especially right-to-left shunts)Streptococcus

Aerobic

Gram-positive cocci Staphylococcus aureus

Viridans streptococci

Streptococcus milleri

Streptococcus pneumoniae

Gram-negative rods

Escherichia coli,

Pseudomonas spp,

Klebsiella pneumoniae,

Proteus spp

The most frequent anaerobes cultured from a brain

abscess

•anaerobic streptococci.

• Bacteroides spp (including B. fragilis).

•Prevotella melaninogenica.

• Propionibacterium.

•Fusobacterium.

• Eubacterium.

• Veillonella.

•Actinomyces

Immunocompromised hosts

•Toxoplasma gondii

•Listeria

•Nocardia asteroides

•Aspergillums'

•Cryptococcus neoformans.

•Coccidioides immitis.

• Mucormycosis

CT-Scan

Early cerebritis appears as an irregular area of low

density that does not enhance following contrast

injection.

the lesion enlarges with thick and diffuse ring

enhancement following contrast injection

thin ring which may not be uniform in thickness

MRI

•more sensitive for early cerebritis

•more sensitive for detecting satellite lesions

•More accurately

•estimates the extent of central necrosis

•ring enhancement,

•cerebral edema

•Better visualizes the brainstem

LP

a lumbar puncture (LP) is contraindicated

Decompression of the cerebrospinal fluid (CSF)

pressure associated with brain stem herniation

in 1.5 to 30 percent of cases

Culture and biopsy

•Gram's stain

• aerobic

• anaerobic

• mycobacterial

•fungal culture

Antibiotics

•Penicillin G covers most mouth flora including both aerobic and anaerobic

streptococci.

•Metronidazole readily penetrates brain abscesses, Given the excellent

intralesional concentrations and the high probability of anaerobes.

•Ceftriaxone covers most aerobic and microaerophilic streptococci also covers

many Enterobacteriaceae

•Ceftazidime should be used when brain abscess complicates a neurosurgical

procedure or in cases where the abscess culture grows P. aeruginosa.

•Vancomycin should be included when brain abscess follows penetrating head

trauma or craniotomy or when S. aureus bacteremia is documented

Aspiration

•preferred for speech areas and regions of the

sensory or motor cortex and in comatose

patients.

•Not preferred for:•Early cerebritis without evidence of cerebral

necrosis.

•Abscesses located in vital regions of the brain or

those inaccessible to aspiration

Surgery

•indications for excision after initial aspiration

and drainage:

•Traumatic brain abscesses (to remove bone chips

and foreign material)

•Encapsulated fungal brain abscesses

•Multiloculated abscesses