BRAIN ABSCESS

BRAIN ABSCESS - PeterKozisek, MD
BASICS
DESCRIPTION
• Single or multiple abscesses within the brain, usually occurring secondary to a focus of infection outside the central nervous system
• May mimic brain tumor, but evolves more rapidly (days to a few weeks)
• Starts as a cerebritis, becomes necrotic, and subsequently becomes encapsulated
• Synonym(s): Cerebral abscess
ALERT
Geriatric Considerations
Age does not affect outcome as much as the abscess size and state of neurological dysfunction at presentation.
Pediatric Considerations
• About 1/3 of the cases in pediatric age group
• Rarely found in infants 1 year of age
• Cyanotic congenital heart disease frequently associated
GENERAL PREVENTION
• Adequate treatment of otitis media, mastoiditis, dental abscess, other predisposing factors
• Prophylactic antibiotics after compound skull fracture or penetrating head wound
EPIDEMIOLOGY
• Incidence/prevalence in the US: Infrequent
• Predominant age: Median age 30-40 years
• Predominant sex: Male > Female (2:1)
RISK FACTORS
• AIDS
• Immunocompromised
• IV drug abuse
Genetics
No known genetic pattern
ETIOLOGY
• Direct extension from otitis, mastoiditis, sinusitis, or dental infection
• Cranial osteomyelitis
• Penetrating skull trauma
• Prior craniotomy
• Bacteremia from lung abscess, pneumonia
• Bacterial endocarditis
• Fungal infection of the nasopharynx
• Toxoplasma gondii (in AIDS patients)
• Cyanotic congenital heart disease
• IV drug use
• No source found in 20%
• Most common infective organisms: Streptococci, staphylococci, enteric Gram-negative bacilli and anaerobes (usually same as source of infection), Nocardia
ASSOCIATED CONDITIONS
• AIDS
• Congenital heart disease


DIAGNOSIS
SIGNS AND SYMPTOMS
History
• Recent onset of headache becoming severe
• Nausea and vomiting
• Mental changes progressing to stupor and coma
• Afebrile or low-grade fever
• Neck stiffness
• Seizures
• Papilledema
• Focal neurological signs depending on location
Physical Exam
• Lumbar puncture often contraindicated
• Search for primary source of infection (chest radiograph, skull film for fracture, or sinus films)
TESTS
• WBC may be normal or mildly elevated
• Culture of abscess contents, predominant organisms include Toxoplasma (AIDS), Staphylococcus (trauma), aerobic or anaerobic bacteria, fungi (rare)
• Blood studies: Mild polymorphonuclear leukocytosis; elevated sedimentation rate
• Special test: Surgical burr hole with aspiration to make a specific bacteriologic diagnosis
ALERT
Drugs that may alter lab results: Prior administration of antibiotics
Imaging
• CT or MRI are the diagnostic methods of choice. The findings are dependent on stages of the abscess.
• Radionuclide 117In-labeled leukocytes may distinguish abscess from neoplasm
Pathological Findings
• Suppuration, liquefaction, and encapsulation, depending on stage of evolution
• Fibrosis
DIFFERENTIAL DIAGNOSIS
• Brain tumors
• Cysticercosis
• Stroke
• Resolving intracranial hemorrhage
• Subdural empyema
• Extradural abscess
• Encephalitis
TREATMENT
PRE-HOSPITAL
Inpatient for close observation, diagnostic evaluation, and specialty consultation (neurology, neurosurgery, or infectious disease)
GENERAL MEASURES
• Palliative and supportive
• Medical therapy
- For surgically inaccessible, multiple abscesses
- For abscesses in early cerebritis stage
- Small (2.5 cm) abscess
- Therapy directed toward most likely organism
Diet
IV fluids if nausea and vomiting present
Activity
Bed rest until infection controlled and abscess evacuated or resolving, then up as tolerated
MEDICATION (DRUGS)
• Antibiotics according to organism if known
• If organism unknown, begin with penicillin G and metronidazole, or chloramphenicol (Chloromycetin), if metronidazole cannot be used
• Add oxacillin or nafcillin if trauma or IV drug user (use vancomycin in penicillin-sensitive patients)
• If Gram-negative organism suspected (otic, GI, GU organ), add 3rd-generation cephalosporin
• Abscess associated with HIV infection assumed to be due to Toxoplasma gondii
- Daily doses of sulfadiazine and pyrimethamine
- Therapy will be lifelong in AIDS patients.
• Anticonvulsants
- Phenytoin until abscess resolved or perhaps longer
- Obtain anticonvulsant levels
• Following a surgical procedure, use corticosteroids to reduce edema, such as Dexamethasone. Taper rapidly. Use is usually limited to 1 week. Continue antibiotics for 6-8 weeks.
• Contraindications: Sensitivity or allergy to any prescribed medications
• Precautions
- Sulfadiazine poorly water-soluble. Patients must maintain adequate hydration or risk developing 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), 5-15 mg (PO, IM, IV) if necessary.
• Significant possible interactions: Refer to the manufacturer's literature.
SURGERY
Surgical therapy
• Mandatory when neurologic deficits are severe or progressive
• Used when the abscess is in the posterior fossa
• 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
• Abscess resulting from trauma
FOLLOW-UP
PROGNOSIS
Survival: >80% with early diagnosis and treatment
COMPLICATIONS
• Permanent neurological deficits
• Surgical complications
• Recurrent abscess
• Seizures
PATIENT MONITORING
• Postsurgical monitoring as needed
• Serial CT or MRI: To confirm progressive resolution, early detection, and management of complications
REFERENCES
1. Graham DI, Lantos PL, eds. Greenfield's Neuropathology. 9th ed. London: Arnold; 2002.
2. Osenbach RK, Loftus CM. Diagnosis and management of brain abscess. Neurosurg Clin North Am. 1992;3:403-420.
3. Rakel RE, ed. Conn's Current Therapy. Philadelphia, PA: Elsevier Saunders; 2005.
4. Ropper A, Victor M, eds. Adams and Victor's Principles of Neurology. 8th ed. New York, NY: McGraw-Hill; 2005.
5. Rowland LD, ed. Merritt's Textbook of Neurology. 10th ed. Baltimore, MD: Williams  Wilkins; 2000.