Brain Abscess

Description of Medical Condition

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). It starts as a cerebritis, becomes necrotic, and subsequently becomes encapsulated.

System(s) affected: Nervous

Genetics: No known genetic pattern

Incidence/Prevalence in USA: Infrequent

Predominant age: Median age 30-40

Predominant sex: Male > Female (2:1)

Medical Symptoms and Signs of Disease

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

What Causes Disease?

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
Intravenous 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

Risk Factors

AIDS
Immunocompromised
IV drug abuse

Diagnosis of Disease

Differential Diagnosis

Brain tumors
Cysticercosis
Stroke
Resolving intracranial hemorrhage
Subdural empyema
Extradural abscess
Encephalitis

Laboratory

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

Drugs that may alter lab results: Prior administration of antibiotics

Disorders that may alter lab results: N/A

Pathological Findings

Suppuration, liquefaction, encapsulation, depending on stage of evolution
Fibrosis

Special Tests

Surgical burr hole with aspiration to make a specific bacteriologic diagnosis

Imaging

CT or MRI are diagnostic methods of choice — findings are dependent on stages of the abscess
Radionuclide 117 IN-labeled leukocytes may distinguish abscess from neoplasm

Diagnostic Procedures

History, physical exam
Lumbar puncture often contraindicated
Search for primary source of infection (chest x-ray, skull film for fracture, sinus films, etc.)

Treatment (Medical Therapy)

Appropriate Health Care

Inpatient for close observation, diagnostic evaluation, and specialty consultation (neurology, neurosurgery, infectious disease)

General Measures

Palliative and supportive
Medical therapy
- For surgical inaccessible, multiple abscesses
- For abscesses in early cerebritis stage
- Small (< 2.5 cm) abscess
- Therapy directed toward most likely organism

Surgical Measures

Surgical therapy
- Mandatory when neurologic deficits are severe or progressive
- Used when the abscess is in the posterior fossa
- Abscess drainage — (via needle) under stereotactic CT guidance through a burr hole under local anesthesia, is most rapid and effective method. May be repeated if needed.
- Craniotomy — if abscess is large or multilocular
- Abscess resulting from trauma

Activity

Bedrest until infection controlled and abscess evacuated or resolving, then up as tolerated

Diet

IV fluids if nausea and vomiting present

Patient Education

For patient education materials favorably reviewed on this topic, contact: Brain Research Foundation, 208 S. LaSalle Street. Suite 1426, Chicago, IL 60604, (312)782-4311

Medications (Drugs, Medicines)

Drug(s) of Choice

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, Gl, GU organ) add third-generation cephalosporin
Abscess associated with HIV infection assumed to be due to Toxoplasma gondii — daily doses of sulfadiazine and pyrimethamine. Therapy will be life-long in AIDS patients.
Anticonvulsants — phenytoin until abscess resolved or perhaps longer. Obtain anticonvulsant levels.
Following surgical procedure — corticosteroids to reduce edema. Dexamethasone. Taper rapidly. Use 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 penicillins in patients with renal dysfunction
Monitor serum levels of anticonvulsants
Dose of pyrimethamine required for treatment of toxoplasmosis may approach toxic levels. Should observe for folic acid deficiency and treat with folinic acid (leucovorin) 5-15 mg (orally, IM, IV) if necessary

Significant possible interactions: Refer to manufacturer’s literature

Alternative Drugs

N/A

Patient Monitoring

Postsurgical monitoring as needed
Serial CT or MRI — to confirm progressive resolution, early detection and management of complications

Prevention / Avoidance

Adequate treatment of otitis media, mastoiditis, dental abscess, other predisposing factors
Prophylactic antibiotics after compound skull fracture or penetrating head wound

Possible Complications

Permanent neurological deficits
Surgical complications
Recurrent abscess
Seizures

Expected Course / Prognosis

Survival > 80% with early diagnosis and treatment

Miscellaneous

Associated Conditions

AIDS
Congenital heart disease

Age-Related Factors

Pediatric:

About one third of cases in pediatric age group. Rarely found in infants under 1 year of age.
Cyanotic congenital heart disease frequently associated

Geriatric: Age does not affect outcome as much as abscess size and state of neurological dysfunction at presentation

Pregnancy

N/A

Synonyms

Cerebral abscess

International Classification of Diseases

324.0 Intracranial abscess