Description

• A purulent collection within the brain most commonly arising from hematogenous sources of infection (pulmonary, cardiac, renal), contiguous spread (sinusitis, dental, and mastoiditis), or direct trauma (postoperative, gunshot) (1)[C]
• Symptoms can mimic brain tumors but can progress rapidly (days to weeks)—mean duration of symptoms around 8.3 days.
• Treatment includes IV antibiotics, stereotactic aspiration, and/or surgical excision.
• Synonym(s): cerebral abscess

Geriatric Considerations
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.
• Newborns or infants may present with cranial enlargement.
• Frequently associated with cyanotic congenital heart disease (risk of abscess 4–7%)

Epidemiology

• Predominant age: median age 30 to 40 years, although brain abscess occurs at all ages
• Predominant sex: male > female (2:1)

Incidence
Reported range from 0.3 to 1.3 per 100,000 (2); however, rates are increased in immunocompromised patients and in developing countries; approximately 2,000 cases a year in the United States

Etiology and Pathophysiology

• Abscess formation can result from contiguous spread, hematogenous spread, or direct trauma.
• Hematogenous spread most often occurs from bacteremia related to lung abscesses, pneumonia, or endocarditis.
• Hematogenous spread usually occurs in the middle cerebral artery (MCA) territory at the junction of the gray-white matter (3)[C].
• Direct extension occurs from otitis, mastoiditis, sinusitis, or dental infections.
• Fungal infection of the nasopharynx
• Contiguous spread from odontogenic and sinus infections frequently present with frontal lobe abscesses
• Contiguous spread from mastoiditis typically present with temporal lobe or cerebellar abscesses, although widespread use of antibiotics for otitis has decreased the incidence of this presentation.
• Four stages of abscess formation include early and late cerebritis followed by early and late capsule formation (1).
• Most common organisms: streptococci, staphylococci (especially after neurosurgery), enteric gram-negative bacilli, anaerobes (usually same as source of infection), Nocardia, fungi, or polymicrobial
• Toxoplasma gondii (HIV/AIDS patients)
• Most common fungal sources include Aspergillus sp., Candida sp., and Zygomycetes.
• Risk factors for fungal infection include immunocompromised, penetrating CNS trauma, and immunocompetent hosts in fungal endemic areas.
• Amebic brain abscess, amebiasis, amebic dysentery

Genetics
Associated with single nucleotide polymorphisms in the ICAM-1 and MCP-1 genes (4)[C]

Risk Factors

• HIV/AIDS
• Immunocompromised state (e.g., organ transplantation)
• IV drug abuse
• Penetrating skull trauma
• Prior craniotomy
• Cyanotic congenital heart disease
• Dental or lung infections
• Cerebrovascular accidents

General Prevention

• Treat potential sources of infection: otitis media, mastoiditis, sinusitis, dental abscess, other ear/nose/throat (ENT) infections.
• Prophylactic antibiotics after compound skull fracture or penetrating head wounds

Commonly Associated Conditions

• AIDS
• Congenital heart disease
• Cardiac vegetations
• Diabetes
• Cirrhosis
• Organ transplantation (solid organ and hematopoietic stem cell)
• Vitamin K deficiency
• Hereditary hemorrhagic telangiectasia