Brain abscess

Brain abscess

OVERVIEW:

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)

SIGNS AND SYMPTOMS:

• 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

CAUSES:

• 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

DIFFERENTIAL DIAGNOSIS:

• Brain tumors
• 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

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
• Therapy directed toward most likely organism
• Small (< 2.5 cm) abscess

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

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, GI, 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 require 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

FOLLOW UP

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 AND 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
Others: N/A

PREGNANCY:

N/A

SYNONYMS:

Cerebral abscess

ICD-9-CM:

324.0 Intracranial abscess

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Medical Diagnosis » B » Brain abscess