• Bacteria are the most common causes of brain abscesses.
• Streptococcus sp. and Staphylococcus sp. are the two most common cultured microorganisms.
• Neonates typically develop abscesses after a gram-negative meningitis (Proteus and Citrobacter)
• A single organism is found in about 70% of patients.
• Anaerobic organisms are being found with increasing incidence with improved laboratory and culture techniques.
• Fungi and protozoa are common with immunocompromised patients.

• Microorganisms enter the brain parenchyma by contiguous or hematogenous (metastasis) pathways.
• Cyanotic congenital heart disease patients tend to have abscesses in the middle meningeal artery distribution: frontal, parietal, and temporal lobes.
• Frontal abscesses are commonly seen with frontal sinusitis.
• Temporal, parietal, or cerebellar abscesses tend to occur with mastoiditis or otitis media infections.
• Brain abscesses can occur anywhere in the brain parenchyma, regardless of a predisposing risk factor.

• Cyanotic congenital heart disease (CCHD)
• Otolaryngologic infections such as sinusitis, mastoiditis, chronic otitis media, or cholesteatomas
• Meningitis (especially with neonates)
• Penetrating head trauma
• Surgical manipulation of the brain (ventriculoperitoneal shunts)
• Esophageal manipulation (sclerotherapy or dilation)
• Cystic fibrosis
• Dental infections
• Lung infections
• Any site of infection (osteomyelitis, orbital, cellulitis, etc.)
• Immunocompromised patients
• Unknown etiology is found in about 30% of patients.

• Incidence is about 2 to 3 per 10,000 general hospital admissions.
• A majority of children are male (2:1 male-to-female predominance).
• Average age of presentation is about 7 years of age.
• About 2% to 4% of children with CCHD will develop a brain abscess. (Tetralogy of Fallot is the most common CCHD.)

• A high index of suspicion is required to diagnose a brain abscess. A delay in diagnosis or performing a lumbar puncture (LP) for suspected meningitis increases mortality and morbidity.
• With the advent of computed tomography (CT) and magnetic resonance imaging (MRI) scans, the mortality rate has dropped from 30% to 14% or less.
• Multiple abscesses, coma on presentation, less than 2 years of age, performance of an LP, and rupture of abscess into the ventricle carry a higher mortality rate.
• About 30% to 40% of patients will have some morbidity. This ranges from seizures, hemiparesis, focal neurological deficits, and hydrocephalus, to cognitive/behavior problems.

• Infectious: meningitis, encephalitis, subdural empyema, epidural abscess
• Vascular: venous sinus thrombosis, migraine, cerebral infarct, cerebral hemorrhage
• Miscellaneous: primary or secondary tumor, pseudotumor cerebri

• It should be noted that the location of the brain abscess or abscesses will often influence the history of presentation and physical examination.
• The classic triad of fever, headache, and focal neurologic findings occurs in less than 30% of cases.
• Headache is the most common complaint.
• The average duration of symptoms prior to diagnosis is about 4 weeks.
• Vomiting and mental status changes can often be the presenting chief complaints.
• Neonates often have a history of meningitis before developing a brain abscess.
• Questions should focus on acute or chronic otolaryngologic infections such as sinusitis, chronic otitis media, and mastoiditis, as well as a history of cholesteatomas.
• Cyanotic congenital heart disease (CCHD) should be determined, as well as a partially repaired CCHD

• Neonates may present with a full fontanel, increasing head circumference, seizures, or vomiting.
• Older children may have signs of increasing intracranial pressure, such as papilledema, focal neurologic deficit, and hemiparesis.
• Meningeal signs are found in 30% of patients.
• Ataxia is seen in cerebellar lesions.

• About 40% of children will not have fevers.
• In older children, consider the possibility of a frontal abscess extending from a bacterial sinusitis, especially with complaints of severe headache and symptoms of prolonged sinusitis.

• CBC may be mildly elevated, and less than 10% will show a left shift.
• Sedimentation rates (ESR) are poor indicators of brain abscesses.
• Electrolytes may show a low sodium, indicating SIADH.
• A lumbar puncture (LP) is contraindicated if any mass lesion is suspected, but if CSF is obtained, it may show a mild-to-moderate pleocytosis (20% of patients may have normal values); the opening pressure is always elevated; glucose may be decreased in 30% of patients; the protein is elevated in 70% of cases; and only 10% of cultures are positive, unless the abscess ruptures into the ventricles.

• Broad-spectrum antibiotics should be started at the time of diagnosis until identification of the microorganism is determined. At that time, the antibiotics can be tailored to the offending microorganism.
• Most brain abscesses are surgically removed. A few may require CT-guided aspiration.
• When multiple abscesses are found on CT scan, one lesion should be aspirated to determine the identification of the microorganism.
• Some patients are managed successfully with antibiotics alone.
• Antifungals should be considered with immunocompromised patients.
• The use of steroids is controversial.
• If a patient is manifesting signs and symptoms of increased intracranial pressure (Cushing triad: bradycardia, hypertension, and abnormal respirations), or if the patient is comatose and is unable to protect his/her airway, the patient should be intubated, hyperventilated, and given mannitol.
• Those patients with unknown predisposing factors should be evaluated by cardiology, dental, and otolaryngology.

• Neonates and older patients may be discharged with home physical therapy and home nursing for intravenous antibiotics.
• Patients will need intravenous antibiotics for a total of 3 to 4 weeks; some may require longer courses of antibiotics.
• Some children will need follow-up CT scans.
• Follow-up with neurosurgical, rehabilitation, and neurology clinics is usually required.
• Some children may need in-patient rehabilitation services.

Q: Do all brain abscesses require surgery?
A: No. Some will regress with antibiotics and follow-up with MRI.

Q: What is the best way to diagnose an abscess.
A: Performing a CT or MRI. LP is contraindicated with mass lesions.

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