Brain Abscess and Subdural Empyema
|Publication: 01/08/2008 --|
|Last review: 10/01/2019|
|Next review: 01/01/2022|
|Approved By: Improving Antimicrobial Prescribing Group|
|Copyright© Leeds Teaching Hospitals NHS Trust 2019|
This Clinical Guideline is intended for use by healthcare professionals within Leeds unless otherwise stated.
Guideline for Management of Brain Abscess and Subdural Empyema
Brain Abscess and Subdural Empyema
Unfortunately, there are no laboratory data that are pathognomic of brain abscess. WCC may be normal. CRP is usually elevated in up to 60% of patients, sometimes may be normal.
Recommendation: Blood cultures should be obtained when a diagnosis of brain abscess is suspected.
Recommendation: Lumbar puncture (LP) should be deferred in any case for which brain abscess is suspected because of the potential for CNS herniation and low likelihood of positive cultures.
The presence of any focal neurological finding or papilledema is an absolute indication for CT imaging prior to LP. CT scanning, preferably with contrast administration, provides a rapid means of detecting the size, the number, and the location of abscesses, and it has become the mainstay of diagnosis and follow-up care. MRI scanning demonstrates soft-tissue resolution and imaging details superior to CT scan (early recognition of cerebritis). An abscess appears as a ring-enhancing, space demanding process. The ring of enhancement is usually quite linear without the heterogeneous appearances characteristic of a malignant glioma. The most frequent abscess locations are frontal, temporal or cerebellar. They are usually sub-cortical, but small abscesses may abut the grey-white matter interface in the middle cerebral artery territory. A CT or MRI scan may also reveal an infected source such as a paranasal sinus or an ear infection.
Serial CT or MRI scans are crucial because abscesses may enlarge despite antibiotic treatment. If neurological deterioration occurs as a consequence of mass effect, surgical removal may become necessary.
Recommendation: Brain abscess pus (collected in a sterile universal container, NOT SWAB) should be sent to Microbiology for urgent microscopy, culture and sensitivity whenever possible.
The treatment for brain abscess is a team approach, with collaboration between a Microbiologist, neuroradiologist, and neurosurgeon. No randomized controlled trials of therapies for brain abscess have been conducted because of the relative infrequency.
Brain abscesses are frequently polymicrobial, the most common causative organisms in clinical series have been microaerophilic streptococci and anerobic bacteria. Additional organisms such as Staphylococcus aureus and Enterobacteriaceae (“coliforms”) are also seen depending on the underlying source.
Initial empirical therapy needs to be commenced as soon as the diagnosis is established and should be tailored to cover the most likely pathogens in individual cases depending upon the location of the abscess and predisposing focus (dental, paranasal sinuses, otogenic etc.). In most cases, attempts to biopsy the lesion to obtain a specimen for culture are essential, since the isolation of pathogenic bacteria allows for more selective antimicrobial therapy.
Abscesses require regular imaging follow-up and if on subsequent imaging the abscess appears to be re-accumulating, further drainage may be required. Very occasionally simple burr hole drainage is insufficient and in these cases (especially peripherally located abscesses) consideration should be given to excising the abscess. Abscesses may be associated with significant oedema and the use of Mannitol and/or steroids may be considered – although the use of the latter in the setting of infection is not ideal. Cerebral abscess formation is associated with a significant risk of epilepsy and while prophylactic administration with anticonvulsants in most forms of neurosurgery remains unproven, the rate of epilepsy associated with cerebral abscess formation is such that it is reasonable to consider giving prophylactic anticonvulsants. The installation of antibiotics into the abscess cavity is not recommended. One of the risks – both from treatment and spontaneously is the rupture of the abscess into the ventricular system. This is associated with an 80% mortality rate. If rupture does occur, the recommendation is for a craniotomy to be performed and the abscess excised and at the same time for the ventricular system to be “washed out” using normal saline. At the end of the procedure an EVD should be placed so that intrathecal antibiotics can be administered.
|Empirical Antimicrobial Treatment|
*Dose may be increased to 3g in certain instances.
There have been a number of more recent case reports demonstrating successful non-operative treatment of brain abscess with antibiotics alone. This approach may be appropriate for clinically stable patients who are poor candidates for surgery or for patients with surgically inaccessible lesions. Small lesions (2 cm) located in the better-vascularized cortical areas are more likely to respond to antibiotics alone. Medical treatment alone should not be used when the diagnosis is in doubt or when pathological confirmations are not available.
Treatment of Primary Focus
|Directed Antimicrobial Treatment (when microbiology results are known)|
Targeted Antimicrobial Therapy
**Dose adjusted according to estimated Creatinine clearance; need to monitor Vancomycin trough levels.
|Duration of Treatment|
Recommended duration of therapy are:
[Evidence Level C]
The appropriate duration of antimicrobial therapy for brain abscess remains unclear. The recommendations based on past clinical practice favour a minimum of 4-6 weeks of therapy if the abscess has been excised or aspirated or 6-8 weeks, if the patient has been treated conservatively. More recently, shorter durations of antibiotic therapy have been proposed provided the aetiological organisms are susceptible and that adequate surgical drainage can be established based on correlation between clinical progress and CT findings.
CT scans are unreliable in measuring response to treatment since radiological changes lag behind both the reduction in size of the cavity and the clinical response. Provided the patient remains stable, repeating the scan at weekly intervals for 2 weeks and then at fortnightly intervals for a further 1-month enables re-accumulation of the abscess to be detected at a pre-clinical phase.
|Switch to oral agent(s)|
Recommendation: Patients can be switched onto oral therapy when:
Please contact Microbiology to discuss oral antimicrobial options.
Brain abscess and subdural empyema
|Target patient group:|
|Target professional group(s):||Pharmacists
Secondary Care Doctors
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Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases; Seventh edition. 2010
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Chun CH, Johnson JD, Hofstetter M, et al. Brain abscess: A study of 45 consecutive cases. Medicine. 1986; 65: 415-431.
Improving Antimicrobial Prescribing Group
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