Brain abscess

Brain abscess is a focal intracranial infection, most commonly caused by bacteria, that can produce neuropsychiatric and multisystemic manifestations, with clinical features varying according to the location, size, number, causative organism, route of infection, and host immune status. A distinctive presentation may include the combination of progressive headache, altered mental status or behavioural change, seizures or focal neurological deficits, and evidence of a contiguous or distant infectious source.

Exposure clues include recent or ongoing dental infection, sinusitis, otitis or mastoiditis, infective endocarditis, pulmonary infection, penetrating or traumatic cranial injury, neurosurgery, or conditions associated with impaired immunity. Brain abscess may also arise through dissemination from a distant infectious focus, and in some cases no source is identified.

It can present with psychiatric features such as behavioural change, irritability, agitation, apathy, impaired concentration, cognitive impairment, confusion, or altered mental status. Frontal lobe abscesses may present particularly with subtle behavioural or personality change. Psychotic symptoms have also been reported, but these are uncommon and the available literature does not consistently establish to what extent they occur independently of delirium.

Other characteristic features include headache, fever, nausea and vomiting, seizures, focal neurological deficits, gait or coordination abnormalities, cranial neuropathies, meningism, and features of raised intracranial pressure such as papilloedema or reduced consciousness. The classic combination of headache, fever, and focal neurological deficit occurs in only a minority of patients, so its absence does not exclude brain abscess.

From a multisystemic lens perspective, clinical features in other body systems include (but are not limited to):

• Cardiovascular: Infective endocarditis may provide a source for brain abscess, particularly with Staphylococcus aureus or streptococcal infection.

• Respiratory: Pneumonia, lung abscess, bronchiectasis, or other pulmonary infection may serve as a source for dissemination to the brain.

• Hematologic: Leukocytosis with neutrophilia and elevated inflammatory markers may occur, although these findings can be absent, particularly in immunocompromised or more indolent infections. Bacteraemia may also occur.

Early diagnosis is important because brain abscess can progress rapidly to raised intracranial pressure, seizures, neurological deterioration, ventricular rupture, sepsis, or death. Prompt neuroimaging and microbiological assessment are essential, followed by appropriate antimicrobial therapy and neurosurgical drainage or excision when indicated.