The microbiology and recent developments in the diagnosis and management of brain abscess in children are reviewed from Georgetown University School of Medicine, Washington, DC. The intracranial infection originates from various sites: 1) direct extension from chronic otitis media or sinusitis; 2) contiguous spread from venous thrombophlebitis; 3) infected open fractures or surgical sites; and by 4) hematogenous spread from a distant focus (eg. cyanotic congenital heart disease, lung infection, bronciectasis, dental abscess). Clinically, the child presents with fever, headache, drowsiness, seizures, vomiting, papilledema, ataxia, and hemiparesis. Diagnosis may be delayed for up to 2 weeks in 2/3rds of patients, and longer in abscesses localized to the frontal and parietal lobes. The predominant organisms are Staphylococcus aureus, Streptococcus pneumoniae, Streptococcus pyogenes, and alpha-hemolytic streptococci. Lumbar puncture is only considered when a mass and increased intracranial pressure have first been excluded by CT or MRI. Low CSF sugar (<40 mg/dL) occurs in one-third and elevated protein (>40 mg/dL) in two thirds of patients. CSF leukocytes may reach 100,000/mm3 or more when an abscess ruptures. CSF cultures are positive in <10% patients, unless the abscess ruptures. Cultures should include aerobic, anaerobic, fungi, and acid-fast staining. MRI is the preferred imaging method for diagnosis, and a diffusion MRI will differentiate between cerebral tumor, stroke, and abscess. MRI in patients with cerebritis may mimic findings in stroke. Since the advent of MRI, mortality has fallen by 90% and is <5-15%. EEG may show a focus of high voltage slow waves, but is less sensitive and non-specific. Ultrasonography and contrast enhanced CT may detect subdural empyema in infants and differentiate it from subdural effusion. Treatment. Antimicrobial therapy and measures to control the increased intracranial pressure are essential in the early stages, before encapsulation has occurred. Once the abscess has formed, surgical excision or drainage with a long course of antibiotics (4-8 weeks) is the treatment of choice. Antibiotics alone may be successful in patients who are stable without increased intracranial pressure, with symptoms for less than 2 weeks, and an abscess <2 cm in diameter. Repeated CT-guided needle aspirations are preferred to complete excision in patients with multiple abscesses or concomitant meningitis. Corticosteroids are controversial: steroids can retard encapsulation, increase necrosis, reduce antibiotic penetration into the abscess, alter CT images, and produce a rebound effect when discontinued. When used to reduce cerebral edema and increased intracranial pressure, steroid therapy of short duration may be life saving. Outcome correlates with abscess size and mass effect: those <1.7 cm (range 0.8-2.5 cm) usually respond to antimicrobial therapy alone, while those with an average size of 4.2 cm (range 2.0-6.0 cm) require surgical intervention. Duration of symptoms before diagnosis is also important: those with symptoms <1 week have a more favorable outcome than those with symptoms >1 week. Early antibiotic therapy can prevent progression from cerebritis to formation of abscess and need for surgery, but proper selection of antibiotics, with regard to organism sensitivity and penetration into abscess and CNS, requires expert consultation. 
COMMENT. The experience of brain abscess at Children’s Hospital, Boston, between 1981 and 2000, is reported by Goodkin et al. 2004 (see Ped Neur Briefs June 2004;18:43-44). Congental heart disease was the most common predisposing factor. In post-1981 compared to pre-1981 cases (n=55 cf 94), the annual rate of abscess was similar, those associated with otitic or sinus infection had decreased in frequency, abscess in infants was more common, acute immunosuppressive disease was a more frequent predisposing factor, treatment with antibiotics alone had become successful in >20% cases, but mortality rate had shown no significant change (24% vs 27%). Despite improvements in diagnosis using neuroimaging, brain abscess continues to result in high rates of neurologic impairment and death. A greater awareness of presenting symptoms and predisposing factors and earlier diagnosis may be expected to improve outcome in the future. New-onset headache and seizure in a child with congenital heart disease or recent ear or sinus infection, and especially a positive culture for Streptococcus milleri (S intermedius), or fungal disease in an acutely immunosuppressed patient, should alert the physician to the diagnosis of cerebral abscess.