AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

Once a relatively common disease with a dire outcome, brain abscesses are now less common. Dental abscess, sinusitis, and middle ear infection were the most common causes of this disease; treatments for these predisposing illnesses are more efficacious, and this has reduced the incidence of intracranial abscess. Morbidity and mortality have also decreased because of advances in diagnostic modalities, antibiotic regimens, and surgical techniques. However, new disease pathogens have renewed concern about the diagnosis and treatment of brain abscess.

Pathophysiology

Brain abscess usually occurs secondary to a focus of infection outside of the CNS. An abscess usually begins as cerebritis and progresses from focal necrosis to form encapsulated lesions.

Frequency

United States

Brain abscess is rare in the general population; however, immunocompromised patients have increasing incidence of brain abscess, often with fungal or protozoan organisms.

Mortality/Morbidity

• Mortality from brain abscess is currently approximately 10%.
• Morbidity in survivors is generally due to residual focal defects, increased incidence of seizures due to scar tissue foci, or neuropsychiatric changes.

Race

No compelling evidence exists for racial differences in the incidence of brain abscess.

Sex

Brain abscess occurs twice as often among men than women.

Age

Incidence peaks in the fourth decade of life.

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

• Typically, patients present to the emergency department (ED) with headache, low-grade fever, and either a focal neurologic defect or a seizure. None of these symptoms are pathognomonic for brain abscess. Patients often present early in their course with no other symptom than headache (seen in at least 70-90% of patients with brain abscess).
• Patients may complain of nausea, vomiting, or stiff neck.

Physical

• Fever is typically low grade.
• Altered mental status ranges from subtle personality changes through drowsiness to full-blown coma.
• Nuchal rigidity occurs in about 25% of cases.
• Focal neurologic signs can signal increasing cerebral edema around the abscess.
• Seizures are typically grand mal.
• Papilledema indicates the disease process is well advanced and increased intracranial pressure is present.

Causes

• Most brain abscesses originally stemmed from nasopharyngeal infections such as otitis media, mastoiditis, and sinusitis. Because of improved antibiotic therapy, these sources now account for approximately 40% of cases.
• Hematogenous spread from remote primary infection accounts for nearly 30% of cases. In the past, pulmonary infections traditionally were cited as principal sources. This pattern is changing; dental infections are increasingly the primary locus.
• Direct seeding from trauma or neurosurgical procedure causes 10% of cases.
• In the past, approximately 20% of cases were considered to be either idiopathic or of undetermined origin. In all of these cases, etiologic organisms were overwhelmingly bacterial, including aerobic (ie, Streptococcus milleri, Streptococcus viridans, Staphylococcus aureus, beta-hemolytic streptococci) and anaerobic species (ie, Bacteroides species, anaerobic streptococci).
• Increasingly, opportunistic infection is a cause of brain abscess. Fungal and protozoan organisms, which follow such immunosuppressive diseases as HIV and chronic tuberculosis (TB), are typically implicated in these cases. Such organisms as Toxoplasma gondii and Nocardia, Aspergillus, and Candida species now constitute the most common sources of brain abscesses in several inner-city EDs located in AIDS-endemic zones.

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

Cerebellopontine angle tumor
Extradural abscess
Pediatric AIDS
Subdural empyema

Recent evidence suggests that a strong statistical association of pulmonary arteriovenous malformation (PAVM) and brain abscess exists. To date, no evidence of a causal relationship between the two exists, but if a patient is known to have PAVM, an increased level of suspicion should exist for brain abscess if symptoms suggest the diagnosis. (Conversely, some have called for screening for PAVM in all patients with brain abscess in order to avoid missing this potentially life-threatening disorder.)

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Lab Studies

• Laboratory tests are rarely helpful in establishing a diagnosis.
• • The WBC is often slightly elevated.
  • The erythrocyte sedimentation rate (ESR) may be elevated in as many as 60% of patients.
  • Blood cultures should be obtained when the diagnosis is suspected. Hematogenous spread may be the source as noted above, and a positive blood culture result may help guide therapy once an organism and sensitivities are identified.

Imaging Studies

• CT imaging of the brain (with and without contrast) is the most readily available study for establishing diagnosis of brain abscess in the ED.
• • Early in the course, abscess appears as a low-density, irregular zone that does not enhance in the presence of intravenous contrast
  • Classically, as the disease progresses, a distinctive "ring enhancement" appears on contrast-enhanced CT, as the abscess wall thickens.
  • Rarely, a well-organized abscess wall fails to generate such ring enhancement. Such false-negative results should not have an impact on ED care or disposition; they have more implications for inpatient care, where the timing of surgical intervention is dictated by response to preliminary intravenous antibiotics and subsequent organization of the abscess wall.
• MRI is increasingly becoming useful for establishing the presence of a brain abscess. Earlier technical problems with enclosed scanners and the physical isolation of MRI suites have been addressed by newer generation systems and inclusion of integral MRI suites in radiology departments. The principal difficulty with using MRI in ED diagnosis is availability of ancillary personnel to perform studies after hours. Fortunately, CT is generally sufficient to make the preliminary diagnosis, which mandates neurosurgical consultation and admission to the hospital.

Procedures

• Lumbar puncture (LP) should be deferred in any case for which brain abscess is suspected because of the potential for CNS herniation and death.
• The presence of any focal neurologic finding or of papilledema is an absolute indication for CT imaging prior to LP.

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Prehospital Care

Rapid transport is the key component of prehospital care for suspected intracranial abscess. The only helpful in-field intervention is endotracheal intubation and hyperventilation for selected (critically ill) patients.

Emergency Department Care

• The initial evaluation is dictated by the severity of the patient's condition.
• Emergent intubation using a cerebroprotective rapid sequence induction regimen should be considered for patients with focal neurologic findings or with decreased level of consciousness. When indicated, intubation, hyperventilation, and stabilization should precede contemplating diagnostic procedures.
• Patients who present with seizure, in whom a high index of suspicion exists for brain abscess, also require intubation and hyperventilation. Seizures should be treated aggressively as well in order to decrease the risk of sustained increases in intracranial pressure.
• Stable patients whose presentation suggests the diagnosis may undergo CT scan after initial evaluation. Close monitoring of neurologic status is essential and having at least one nurse or advanced provider in attendance while the patient is undergoing imaging is probably advisable.
• Antibiotics should be administered as early as possible in the patient's course in the ED. These may be given prior to imaging in cases where the diagnosis is very strongly suspected.

Consultations

Once the diagnosis is clear, immediate neurosurgical consultation is mandatory.

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

The goals of medical therapy are to control the infection and to prevent complications. In almost all cases, definitive treatment of brain abscess requires surgical drainage.

Drug Category: Antibiotics

In the ED, empirical regimens of antibiotic therapy are the first-line pharmacologic treatment for brain abscess. They must cover a broad spectrum of both aerobic and anaerobic bacterial pathogens.

Drug Category: Corticosteroids

The anti-inflammatory effects of steroid therapy can decrease cerebral edema, reducing intracranial pressure (ICP). These benefits are offset somewhat by the fact that steroid use decreases antibiotic penetration into the abscess and may slow encapsulation of the abscess site.

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Further Inpatient Care

• At the discretion of the consulting neurosurgeon, most abscesses are managed by a period of intravenous antibiotic therapy to allow the lesion to organize and to decrease local extension of the infection. After that period, definitive treatment is provided by aspiration, incision and drainage, or excision.
• At present, most neurosurgeons use nonoperative management (ie, prolonged courses of parenteral antibiotics) only in rare cases, such as an abscess at an inoperable site.
• Such cases have become more rare, as many abscesses that were once inoperable can now be reached by stereotactic aspiration guided by precision mapping of the lesion's location by CT or MRI. Reports in the literature document MR fluoroscopy being used to guide aspiration instead of stereotactic aspiration.
• Some interest exists in the possible role of hyperbaric oxygen as an adjunct therapy to the initial phase of treatment with intravenous antibiotics. Reports suggest that in children such adjunct therapy may reduce the length of inpatient stay by decreasing the time needed for an effective course of stabilizing antibiotics; however, the number of cases studied to date is small.

Transfer

• Lack of neurosurgical coverage constitutes an absolute indication for transfer to a medical center that has such support.

Complications

• Uncal or tonsillar herniation due to increased ICP
• Hemorrhage into the abscess
• Rupture of abscess into ventricles or subarachnoid space (This complication is generally lethal.)

Prognosis

• Survival rates are excellent.
• Characteristics associated with an excellent prognosis include the following:
• • Young age
  • Absence of severe neurologic defect on initial presentation
  • Absence of neurologic deterioration during initial workup
  • Absence of comorbid disease
• In patients with signs of herniation on initial presentation, mortality rate exceeds 50%.

Patient Education

• For excellent patient education resources, visit eMedicine's Infections Center, Brain and Nervous System Center, and Brain and Nervous System Center. Also, see eMedicine's patient education articles Brain Infection, Antibiotics, and Brain Infection.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Failure to obtain a brain CT scan in patients with headache and new neurologic defect
• Failure to heed family concerns about unusual patient behavior when other symptoms suggestive of brain abscess are present

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

• Alderson D, Strong AJ, Ingham HR, Selkon JB. Fifteen-year review of the mortality of brain abscess. Neurosurgery. Jan 1981;8(1):1-6. [Medline].
• Bernardini, GL. Diagnosis and management of brain abscess and subdural empyema. Curr Neurol Neurosci Rep 2004 Nov. 2004;4(6):448-56. [Medline].
• Boviatsis EJ, Kouyialis AT, Stranjalis G, et al. CT-guided stereotactic aspiration of brain abscesses. Neurosurg Rev. 2003;26(3):206-9. [Medline].
• Gallitelli M, Lepore V, Pasculli G, et al. Brain abscess: a need to screen for pulmonary arteriovenous malformations. Neuroepidemiology. 2005;24(1-2):76-8. [Medline].
• Kastrup O, Wanke I, Maschke M. Neuroimaging of infections. NeuroRx. 2005;2(2):324-32. [Medline].
• Kurschel S, Mohia A, Weigl V, et al. Hyperbaric oxygen therapy for the treatment of brain abscess in children. Childs Nerv Syst. 2005;May 5:[Medline].
• Levy RM, Berger JR. Neurosurgical aspects of human immunodeficiency virus infection. Neurosurg Clin N Am. Apr 1992;3(2):443-70. [Medline].
• Mamelak AN, Mampalam TJ, Obana WG, et al. Improved management of multiple brain abscesses: a combined surgical and medical approach. Neurosurgery. 1995;36(1):76-85. [Medline].
• Marshman LA, Connor S, Chandler CL. Persistent absence of ring-enhancement on CT with an encapsulated brain abscess. Br J Neurosurg. 2004;18(4):377-82. [Medline].
• Osenbach RK, Loftus CM. Diagnosis and management of brain abscess. Neurosurg Clin N Am. Apr 1992;3(2):403-20. [Medline].
• Saez-Llorens X. Brain abscess in children. Semin Pediatr Infect Dis. Apr 2003;14(2):108-14. [Medline].
• Sennaroglu L, Sozeri B. Otogenic brain abscess: review of 41 cases. Otolaryngol Head Neck Surg. Dec 2000;123(6):751-5. [Medline].
• Seydoux C, Francioli P. Bacterial brain abscesses: factors influencing mortality and sequelae. Clin Infect Dis. Sep 1992;15(3):394-401. [Medline].
• Unal O, Sakarya ME, Kiymaz N, et al. Brain abscess drainage by use of MR fluoroscopic guidance. Am J Neuroradiol. 2005;26(4):839-42. [Medline].
• Vidal JE, Oliveira AC, Filho FB, et al. Tuberculous brain abscess in AIDS patients: report of three cases and literature review. Int J Infect Dis 9(4):201-7. 2005;9(4):201-7. [Medline].

Article Last Updated: Mar 16, 2006