para>Age does not affect outcome as much as the abscess size and state of neurologic dysfunction at presentation.
Pediatric Considerations
~1/3 of total cases occur in the pediatric age group.
Rarely found in infants <1 year of age
Frequently associated with cyanotic congenital heart disease
EPIDEMIOLOGY
- Predominant age: median age 30 to 40 years, although brain abscess occurs at all ages
- Predominant sex: male > female (2:1)
Incidence
Infrequent, but increasing due to increase in immune-suppressed individuals, opportunistic pathogens, and resistance to antibiotics
ETIOLOGY AND PATHOPHYSIOLOGY
- Hematogenous source is most common overall for single or multiple cerebral abscesses. No source found in 20%.
- The frontal lobe is the most common site.
- Direct extension from otitis, mastoiditis, sinusitis, or dental infection
- Bacteremia from lung abscess, pneumonia
- Bacterial endocarditis
- Fungal infection of the nasopharynx
- Toxoplasma gondii (in AIDS patients)
- Most common organisms: streptococci, staphylococci (especially after neurosurgery), enteric gram-negative bacilli, and anaerobes (usually same as source of infection), Nocardia
- Most common fungal sources include Aspergillus sp., Candida sp., and Zygomycetes.
- Risk factors for fungal infection include immunocompromise, penetrating CNS trauma, and immunocompetent hosts in fungal endemic areas.
- Amebic brain abscess, amebiasis, amebic dysentery
Genetics
No known genetic pattern
RISK FACTORS
- HIV/AIDS
- Immunocompromised state
- IV drug abuse
- Penetrating skull trauma
- Prior craniotomy
- Cyanotic congenital heart disease
GENERAL PREVENTION
- Treat otitis media, mastoiditis, sinusitis, dental abscess, other ear/nose/throat (ENT) infections.
- Prophylactic antibiotics after compound skull fracture or penetrating head wound
COMMONLY ASSOCIATED CONDITIONS
- AIDS
- Congenital heart disease
- Cardiac vegetations
- Diabetes
- Cirrhosis
DIAGNOSIS
HISTORY
- Recent onset of increasingly severe headache
- New focal neurologic deficit
- Altered mental status progressing to stupor and coma
- Nausea and vomiting
- Seizures
PHYSICAL EXAM
- Afebrile or low-grade fever
- Papilledema
- Neck stiffness
- Focal neurologic signs, depending on location
DIFFERENTIAL DIAGNOSIS
- Brain tumors
- Cysticercosis
- Stroke
- Resolving intracranial hemorrhage
- Subdural empyema
- Extradural abscess
- Encephalitis
DIAGNOSTIC TESTS & INTERPRETATION
Abscess culture: Predominant organisms include Toxoplasma (AIDS), Staphylococcus (trauma), aerobic or anaerobic bacteria, and fungi (rare).
- Head CT and MRI are the diagnostic methods of choice. Specific findings depend on stages of the abscess (2)[B].
ALERT
Initial Tests (lab, imaging)
- WBC count may be normal or mildly elevated.
- Blood studies: mild polymorphonuclear (PMN) leukocytosis; elevated ESR
- Culture and susceptibilities of the abscess material
- If available, consider broad-range bacterial rDNA polymerase chain reaction with DNA sequencing (1)[C].
- Search for primary source of infection: Solitary intracerebral abscess suggests a direct contiguous source, such as sinus or ear infection. Multiple abscesses suggest hematologic spread.
- CT provides sufficient diagnostic information in most cases, including skull fracture, sinus infection, or otic source (3)[B].
- Consider echocardiogram, chest x-ray, and chest CT if cardiac or pulmonary source suspected.
- Radionuclide 117In-labeled leukocytes may distinguish abscess from neoplasm.
Diagnostic Procedures/Other
Surgical aspiration to make a specific bacteriologic diagnosis
Test Interpretation
Suppuration, liquefaction, or encapsulation, depending on stage of evolution
TREATMENT
Immediate neurosurgical consultation is indicated for suspected CNS abscess.
GENERAL MEASURES
- Treatment of brain abscess requires a combination of surgical intervention and appropriate antimicrobial therapy.
- Initial medical therapy includes broad-spectrum antibiotics pending determination of the causative organism (4)[A].
- Determining the point of entry and source of infection is critical to effective treatment (5)[C].
- Medical therapy only may be indicated
- For surgically inaccessible lesions or multiple abscesses
- For abscesses in early cerebritis stage
- For small (<2.5 cm) abscesses
- Antibiotic therapy is directed toward the most likely organism if no specific organism can be identified.
- Monitor clinical response to antibiotic therapy.
MEDICATION
- Target antibiotic therapy according to organism and sensitivities, if known.
- Initial empiric treatment according to suspected source of infection
- Antifungal treatment, including amphotericin B, azoles, echinocandins, or flucytosine, in suspected or confirmed fungal cases, as appropriate
- If hematogenous sources are suspected, cover MRSA initially with vancomycin-may be broaden to include metronidazole and a 3rd-generation cephalosporin.
- For dental source, penicillin G and metronidazole are good initial choices.
- For otogenic or sinus source, coverage should include metronidazole and either ceftriaxone or cefotaxime.
- For GI or genitourinary source, consider a 3rd-generation cephalosporin, such as cefotaxime, to cover gram negatives.
- For traumatic source, consider vancomycin plus either ceftriaxone or cefotaxime.
- Hospital-acquired sources, including postsurgical abscess, consider vancomycin and cefepime or ceftazidime.
- If MSSA is isolated, change vancomycin to oxacillin or nafcillin.
- Use vancomycin in penicillin-sensitive patients.
- Generally, a 6- to 8-week course of parenteral antibiotics is required.
- If brain abscess is associated with HIV/AIDS:
- Daily doses of sulfadiazine and pyrimethamine
- Lifelong therapy in AIDS patients
- Anticonvulsants
- Phenytoin until abscess resolves or perhaps longer
- Monitor anticonvulsant levels.
- Following a neurosurgical procedure, use corticosteroids, such as dexamethasone, to reduce edema. Taper rapidly. Use is usually limited to 1 week.
- Contraindications: sensitivity or allergy to any prescribed medications
- Precautions:
- Sulfadiazine is poorly water-soluble. Patients must maintain adequate hydration to avoid crystalluria.
- Decrease dosage of penicillin in patients with renal dysfunction.
- Monitor serum levels of anticonvulsants.
- A dose of pyrimethamine is required for the treatment of toxoplasmosis, which may approach toxic levels. The patient should be observed for folic acid deficiency and treated with folinic acid (leucovorin) 5 to 15 mg (PO, IM, IV), if necessary.
ISSUES FOR REFERRAL
Neurosurgical referral for all patients. Consider infectious disease and neurology consultations if available.
SURGERY/OTHER PROCEDURES
- Surgery is mandatory when neurologic deficits are severe or progressive.
- Surgery is often used when the abscess is in the posterior fossa or is the result of trauma.
- Type of surgical treatment depends on the patient's clinical status, the neuroradiographic characteristics of the abscess, and the experience of the surgeon(s) carrying out the procedure (5)[C].
- Abscess drainage via a needle under stereotactic CT guidance through a burr hole under local anesthesia is the most rapid and effective surgical method of treatment and may be repeated if needed.
- Craniotomy: if abscess is large or multilocular
- In general, similar outcomes for stereotactic-guided drainage or craniotomy (6)[B]
- Hyperbaric oxygen therapy (HBOT) has been reported as an adjunctive therapy for brain abscesses (7)[C].
INPATIENT CONSIDERATIONS
Admission Criteria/Initial Stabilization
Patients with a brain abscess typically require admission to an ICU for close observation, diagnostic evaluation, and specialty consultation (neurology, neurosurgery, or infectious disease).
IV Fluids
IV fluids if nausea and vomiting present
Discharge Criteria
When patient is asymptomatic, afebrile, and responding to therapy as determined by serial imaging studies
ONGOING CARE
FOLLOW-UP RECOMMENDATIONS
- Bed rest until infection controlled and abscess evacuated or resolving, then as tolerated
- May need long-term rehabilitative care
Patient Monitoring
- Postsurgical monitoring, as needed
- Serial CT or MRI for at least 3 months to evaluate the therapeutic response, confirm progressive resolution, detect new lesions, and manage complications
DIET
IV fluids if significant nausea and vomiting
PATIENT EDUCATION
Brain Research Foundation, 208 S. LaSalle Street, Suite 1426, Chicago, IL 60604; (312) 782-4311.
PROGNOSIS
- The route of spread, the type and virulence of the organism, thickness of the capsule, location and number of abscesses in the brain, and immune status of the host are important determinants of outcome.
- Survival: >80% with early diagnosis and treatment
- In one retrospective analysis, 80% of patients recovered fully or had minimal incapacity. There was a 10% fatality rate in this series.
- Patients with underlying cranial neoplasms or medical conditions have worse outcomes than those with a contiguous focus of infection or posttraumatic abscess.
COMPLICATIONS
- Permanent neurologic deficits
- Recurrent abscess
- Seizures
- Death
REFERENCES
11 Foerster BR, Thurnher MM, Malani PN, et al. Intracranial infections: clinical and imaging characteristics. Acta Radiol. 2007;48(8):875-893.22 Al Masalma M, Armougom F, Scheld WM, et al. The expansion of the microbiological spectrum of brain abscesses with the use of multiple 16S ribosomal DNA sequencing. Clin Infect Dis. 2009;48(9):1169-1178.33 Carpenter J, Stapleton S, Holliman R. Retrospective analysis of 49 cases of brain abscess and review of the literature. Eur J Clin Microbiol Infect Dis. 2007;26(1):1-11.44 Lu CH, Chang WN, Lui CC. Strategies for the management of bacterial brain abscess. J Clin Neurosci. 2006;13(10):979-985.55 Bernardini GL. Diagnosis and management of brain abscess and subdural empyema. Curr Neurol Neurosci Rep. 2004;4(6):448-456.66 Smith SJ, Ughratdar I, MacArthur DC. Never go to sleep on undrained pus: a retrospective review of surgery for intraparenchymal cerebral abscess. Br J Neurosurg. 2009;23(4):412-417.77 Kutlay M, Colak A, Yildiz S, et al. Stereotactic aspiration and antibiotic treatment combined with hyperbaric oxygen therapy in the management of bacterial brain abscesses. Neurosurgery. 2008; 62(Suppl 2):540-546.
CODES
ICD10
- G06.0 Intracranial abscess and granuloma
- A06.6 Amebic brain abscess
- B37.89 Other sites of candidiasis
ICD9
- 324.0 Intracranial abscess
- 006.5 Amebic brain abscess
- 112.89 Other candidiasis of other specified sites
SNOMED
- Abscess of brain (disorder)
- Amebic brain abscess
- Candidal brain abscess (disorder)
- Cerebral abscess (disorder)
CLINICAL PEARLS
- Headache and altered mental status are common presenting symptoms of a brain abscess.
- Determining the portal of entry and source of infection is essential for adequate treatment.
- Treatment of a brain abscess often requires a combination of prolonged antimicrobial therapy (6 to 8 weeks) and surgical intervention to eradicate the infection.
- Serial head CT can help evaluate response to therapy.