Brain Abscess
A brain abscess is an encapsulated, purulent collection of infection within the brain tissue. It develops on a background of adjacent focal infections (sinusitis, otitis media, dental infection), hematogenous spread, trauma-surgery or immunosuppression. The most common organisms are streptococci. Its typical features are headache, fever and focal neurological deficit. Diagnosis is made with contrast-enhanced brain MRI, and treatment is usually a combination of antibiotics and surgical drainage.
最終更新: 2026-06-07
Definition and Formation
A brain abscess is a focal purulent infection that develops when bacterial, fungal or parasitic microorganisms become established in brain tissue. The process progresses through four stages: early cerebritis, late cerebritis, early capsule formation and late capsule formation. Understanding these stages influences treatment choice; antibiotics may be more effective in the early stage, while surgical drainage comes to the fore in a mature (encapsulated) abscess.
Routes of Infection and Organisms
The most common cause is adjacent focal infection: paranasal sinusitis (frontal lobe abscess), otitis media/mastoiditis (temporal lobe or cerebellar abscess) and dental infection. Hematogenous spread occurs on a background of endocarditis, pulmonary infection, cyanotic congenital heart disease or pulmonary arteriovenous malformation and usually leads to multiple abscesses. It is also seen after trauma and surgery and in immunosuppressed patients. The most common organisms are aerobic and anaerobic streptococci; Staphylococcus aureus, gram-negative bacteria, anaerobes and, in immunosuppression, fungal organisms also play a role.
Symptoms
The classic triad of headache, fever and focal neurological deficit is present together in only a proportion of patients. Headache is the most common symptom; it is progressive and severe. Fever is mostly mild to moderate and may be absent in immunosuppressed patients. Focal neurological deficit varies with the location of the abscess (weakness, speech disturbance, visual field loss, imbalance). Seizures, changes in consciousness, nausea-vomiting and papilledema due to raised intracranial pressure may be seen.
Diagnosis
Contrast-enhanced brain MRI is the gold standard for diagnosis. The classic appearance is a thin, smooth-walled ring-enhancing lesion with a fluid-containing center. Diffusion MRI (DWI/ADC) shows restricted diffusion in the abscess center, a feature valuable for distinguishing it from tumor necrosis. Contrast-enhanced CT is used when MRI is unavailable or in an emergency. Blood cultures and laboratory tests are supportive; the definitive organism is identified by culture and Gram staining of the abscess contents obtained at surgery. In the presence of mass effect, lumbar puncture is contraindicated because of the risk of herniation.
Treatment
Treatment is usually a combination of antibiotics and surgical drainage; this combination achieves higher success than antibiotics alone. Empirical antibiotics are selected according to the source and risk factors (for example a third-generation cephalosporin and metronidazole; vancomycin is added with a history of trauma/surgery), and total treatment usually lasts 6-8 weeks. Surgery is indicated when the abscess is large, there is mass effect, it is close to a ventricle or there is no response to antibiotics. The first choice is usually minimally invasive stereotactic aspiration; craniotomy and excision may be preferred for large, multiloculated, fungal or recurrent abscesses.
Source Control and Prognosis
Treating the underlying focus of infection (sinusitis, mastoiditis, dental infection, endocarditis) is essential to prevent recurrence. After surgery, antibiotics are continued, seizure treatment is given when needed, and follow-up is performed with serial MRI. The main factors affecting prognosis are the location of the abscess, the patient's level of consciousness, the number of abscesses and the causative organism. With modern treatment outcomes are generally favorable; however, some patients may be left with permanent neurological sequelae (epilepsy, motor deficit, cognitive impairment). Outcomes are individual and cannot be guaranteed.
参考文献
- Greenberg MS. Greenberg's Handbook of Neurosurgery. 10th ed. Thieme; 2023:343-350.
- Brouwer MC, Coutinho JM, van de Beek D. Clinical characteristics and outcome of brain abscess: systematic review and meta-analysis. Neurology. 2014;82(9):806-813.
- Sonneville R, Ruimy R, Benzonana N, et al. An update on bacterial brain abscess in immunocompetent patients. Clin Microbiol Infect. 2017;23(9):614-620.
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