Brain Abscess l: Introduction

A brain abscess is a focal, intracerebral infection characterized by a localized collection of pus within the brain parenchyma, resulting from microbial invasion and the body’s inflammatory response. It progresses through stages: early and late cerebritis, followed by early and late capsule formation, reflecting tissue destruction, immune response, and eventual encapsulation.

Etiology and Pathogenesis

Causative organisms vary with source and host factors, often involving polymicrobial infections, including streptococci, Staphylococcus aureus, Gram-negative bacilli, and, occasionally, fungi or parasites, in immunocompromised individuals. Infection occurs when the blood–brain barrier is disrupted. Spread may occur contiguously (e.g., otitis media, sinusitis), hematogenously (e.g., endocarditis, lung infections), or by direct inoculation (e.g., trauma or surgery).

Risk Factors

Risk increases in individuals with chronic ear or sinus infections, congenital heart disease, immunosuppression, or uncontrolled systemic infections. Conditions like HIV/AIDS, transplantation, or steroid use alter pathogen profiles and disease progression.

Clinical Course and Complications

Symptoms include headache, fever, and focal neurological deficits, varying by location. Supratentorial lesions may cause hemiparesis or speech issues, while infratentorial lesions may produce ataxia or cranial nerve deficits. Raised intracranial pressure can cause vomiting and papilledema, and seizures are common. Complications include meningitis, ventriculitis, and brain herniation.

Diagnosis and Management

Diagnosis relies on imaging, with contrast MRI being the most sensitive. Lumbar puncture is avoided due to the risk. Treatment includes IV antibiotics and often surgical drainage. Corticosteroids may reduce edema in severe cases.

Outcomes have improved with modern care, though delayed treatment or immunosuppression may lead to lasting neurological deficits.

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