Brain abscess

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Summary of Brain abscess

Brain abscess is an abscess caused by inflammation and collection of infected material, coming from local (ear infection, dental abscess, infection of paranasal sinuses, infection of the mastoid air cells of the temporal bone, epidural abscess) or remote (lung, heart, kidney etc.) infectious sources, within the brain tissue. The infection may also be introduced through a skull fracture following a head trauma or surgical procedures.

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Brain abscess

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$Chapter 65 Cerebral Cortex Nervous System Infections BRAIN ABSCESS osms.it/brain-abscess PATHOLOGY & CAUSES ▪ Localized focal necrosis of brain tissue with inﬂammation, usually caused by bacterial infection ▪ Rare (de novo within brain; primary infection typically arises elsewhere, spreads to brain) Sources of infection ▪ Direct implantation ▫ Traumatic inoculation (e.g. head trauma → skull fracture with broken skin → bacterial contamination) ▫ Iatrogenic: contamination through invasive procedures ▪ Local extension from adjacent foci of infection ▫ Ear infection, dental abscess, paranasal sinusitis, mastoiditis, epidural abscess ▪ Hematogenous spread ▫ Distant sources of infection (e.g. organ infection) ▫ Congenital heart disease with right-toleft shunt → loss of pulmonary ﬁltration of microorganisms → abscesses in distribution of middle cerebral artery ▪ Common causative bacterial organisms (abscesses often polymicrobial) ▫ Staphylococcus aureus, Streptococcus, Bacteroides, Enterobacteriaceae, Pseudomonas ▪ Immunocompromised hosts may develop viral/fungal abscesses, commonly caused by poliovirus, Toxoplasma gondii, Cryptococcus neoformans RISK FACTORS ▪ Right-to-left cardiac shunts, bronchiectasis, immunosuppression SIGNS & SYMPTOMS ▪ Classic triad (20% of cases) ▫ Fever, progressively worsening focal neurology, headache ▫ Increased intracranial pressure (ICP) while supine → worse headache early morning, at night/increased ICP stimulates medullary center, area postrema → morning vomiting ▪ Mental status change, seizures, nausea, vomiting, papilledema DIAGNOSIS DIAGNOSTIC IMAGING MRI/CT scan with contrast ▪ Initial immature lesions without capsule: difﬁcult to distinguish from spaceoccupying lesions/infarcts ▪ 4–5 days after initial infection: formation of capsule around necrotic focus → ringenhancing appearance ▫ Intravenous contrast material cannot pass through capsule → accumulation around lesion → bright ring with dark center LAB RESULTS ▪ Lumbar puncture ▫ If intracranial pressure not signiﬁcantly raised ▫ ↑ white cell count, ↑ protein concentration, normal glucose content ▪ Abscess aspirate ▫ Sample obtained via imaging-guided aspirate/during surgical drainage; culture of causative organism → speciﬁc treatment COMPLICATIONS ▪ Ischemia/necrosis of pituitary → pituitary insufﬁciency → Addisonian crisis OSMOSIS.ORG 501$