Signs and Symptoms
- Fever, headache, and neurological problems occur in 20% of people with brain abscess
- The famous triad of fever, headache, and focal neurologic findings are highly suggestive of brain abscess
- Headache is characteristically worse at night and in the morning
- Other symptoms depend on the specific location of the abscess in the brain
- Neurological examination may reveal a stiff neck in occasional cases

Pathophysiology
- Anaerobic and microaerophilic cocci and gram-negative and gram-positive anaerobic bacilli are the predominant bacterial isolates
- Staphylococcus aureus, streptococci, Bacteroides, Prevotella, and Fusobacterium are the predominant organisms
- Less common organisms include Haemophillus influenzae, Streptococcus pneumoniae, and Neisseria meningitidis
- Fungi and parasites may also cause brain abscess, especially in immunocompromised patients
- Other causes include Nocardia asteroides, Mycobacterium, Aspergillus, Candida, and Cryptococcus
- Predisposing conditions include sinus and dental infections, penetrating trauma, pulmonary infections, congenital heart disease, HIV infection, transplantation, and neutropenia

Diagnosis
- The diagnosis is established by a computed tomography (CT) examination
- The immature lesion may be difficult to distinguish from other space-occupying lesions or infarcts of the brain
- Within 4-5 days, the inflammation and dead brain tissue are surrounded with a capsule, giving the lesion a ring-enhancing appearance on CT with contrast
- Lumbar puncture is contraindicated in brain abscess
- Ring enhancement may also be observed in cerebral hemorrhages and some brain tumors, but the presence of fever, focal neurologic findings, and signs of increased intracranial pressure suggest brain abscess

Treatment
- Treatment includes lowering intracranial pressure and starting intravenous antibiotics
- Hyperbaric oxygen therapy (HBOT) reduces intracranial pressure, acts as a bactericide, optimizes immune function, and aids in healing and recovery
- Surgical drainage of the abscess is part of the standard management
- Treatment of the primary lesion and removal of foreign material are crucial
- Exceptions to surgical drainage include Haemophilus influenzae meningitis and tuberculosis

Prognosis and Complications
- Death occurs in about 10% of cases
- People do well about 70% of the time
- Improved ability to image the head has contributed to better prognosis
- More effective neurosurgery has improved outcomes
- More effective antibiotics have also played a role in improving prognosis
- Neurological deficits can occur as a result of brain abscess
- Infection can spread to surrounding structures, such as the meninges
- Abscess rupture can lead to meningitis
- Increased intracranial pressure is a potential complication
- Long-term cognitive and functional impairments may occur in some cases

Prevention
- Prompt treatment of sinusitis and other infections can help prevent brain abscess
- Proper wound care and infection control measures are important
- Vaccination against certain bacterial pathogens can reduce the risk of brain abscess
- Avoiding high-risk behaviors, such as intravenous drug use, can lower the risk
- Regular dental care and oral hygiene can help prevent dental infections that can lead to brain abscess