Brain Abscess: A Pocket of Infection in the Brain — Causes and Treatment

A brain abscess — a focal collection of pus within the brain parenchyma — develops when bacteria or fungi reach the brain and the body's immune response walls them off in a capsule. Despite its name, a brain abscess is not simply an infection — it behaves like a space-occupying lesion, causing raised intracranial pressure, seizures, and focal neurological deficits. Treatment requires a combination of neurosurgery (drainage) and prolonged antibiotics.

How Bacteria Reach the Brain

Direct spread from adjacent infection: The most common route in India. Chronic suppurative otitis media (CSOM — chronic ear infection with discharge) erodes the temporal bone and allows bacteria to track into the adjacent temporal lobe or cerebellum. Chronic sinusitis with frontal lobe abscess. Dental abscess. Mastoiditis.

Haematogenous spread: Bacteria from a distant infection seed the brain via the bloodstream. Sources: infective endocarditis (heart valve infection — the most dangerous); lung abscess; cyanotic congenital heart disease (right-to-left shunting bypasses the lungs' filtering function — multiple abscesses in unusual locations).

Post-traumatic: Penetrating head injury introducing organisms directly.

Symptoms

The classic triad — headache, fever, focal neurological deficit — is present in fewer than 50% of cases, making diagnosis challenging. More common: progressive headache (present in 70%); fever (present in 50% — may be absent if capsule fully walled off); focal deficit (weakness, speech difficulty — depends on abscess location); seizures (25–35%); raised ICP (vomiting, drowsiness).

Treatment

MRI brain with gadolinium: ring-enhancing lesion with central diffusion restriction (DWI bright) — characteristic of abscess. Neurosurgical aspiration or excision: required for abscesses larger than 2.5cm or causing significant mass effect. Antibiotics: 6–8 weeks of high-dose IV antibiotics covering the likely organisms (empirically: ceftriaxone + metronidazole). Treat the source — ear surgery, dental treatment, cardiac evaluation. Sri Anand CNC, Chanda Nagar, Hyderabad. Call +91 90633 66983.