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THE DIAGNOSIS A ND MANAGEMENT O F BRAIN ABSCESS ES Learning Object ives Introduction Development and Pathogenesis Intracranial In fection Pathogen Spectr um Immunosuppresse d Patients Clinical Featur es Investigation MRI Further Neuroim aging Microbiological Investigation s Management Key Points The Diagnosis and Management of Brain Abscesses Stephen Aston Stephen Aston is a Specialist Registrar in Infectious Diseases at the Tropical and Infectious Diseases Unit, Royal Liverpool University Hospital. Following general medical training in Birmingham, he spent time working on clinical trials in vaccine development in Oxford and the 2009-10 influenza pandemic in Liverpool, before taking up his current post. He is particularly interested in immune responses to severe bacterial infections and how this informs vaccine development. Edited by Prof Tom Solomon and Dr Agam Jung This session provides a review of brain abscesses, including a brief description of aetiology and pathogenesis, later focusing on current investigation and best practice in management.

The Diagnosis and Management of Brain Abscesses

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Page 1: The Diagnosis and Management of Brain Abscesses

THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

The Diagnosis and Management of Brain AbscessesStephen AstonStephen Aston is a Specialist Registrar in Infectious Diseases at the Tropical and Infectious Diseases Unit, Royal Liverpool University Hospital.

Following general medical training in Birmingham, he spent time working on clinical trials in vaccine development in Oxford and the 2009-10 influenza pandemic in Liverpool, before taking up his current post.

He is particularly interested in immune responses to severe bacterial infections and how this informs vaccine development.

Edited by Prof Tom Solomon and Dr Agam Jung

This session provides a review of brain abscesses, including a brief description of aetiology and pathogenesis, later focusing on current investigation and best practice in management.

Page 2: The Diagnosis and Management of Brain Abscesses

THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

Learning Objectives

By the end of this session you will be able to:

• Describe the stages of development and pathogenesis of brain abscesses

• Identify the typical spectrum of pathogens implicated in the aetiology of brain abscess

• Define the nonspecific nature of the clinical features of brain abscess

• List the appropriate investigation of possible brain abscess and to identify the important radiological features on CT and MR scanning

• Develop a management plan for patients with brain abscess, including antimicrobial treatment, surgical interventions and adjunctive therapies

Page 3: The Diagnosis and Management of Brain Abscesses

THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

IntroductionBrain abscess is fortunately a relatively uncommon condition, with an incidence of approximately 1 in 100,000 per year.

Prior to pioneering advancements in neurosurgical techniques in the late 19th century, brain abscesses were invariably fatal. The development of effective anti-microbial agents following the Second World War secured further improvements in prognosis.

With the inception of modern neuroimaging techniques allowing earlier diagnosis, mortality rates have fallen further, presently between 5 and 15%. However, debilitating sequelae such as seizures, paresis and cognitive impairment remain common.

This session outlines the pathogenesis, aetiology and typical clinical features of brain abscess. Approaches to diagnosing the condition are described before reviewing current management strategies.

MRI (T1 + contrast) showing a small ring-enhancing lesion

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THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

Stages of Development and Pathogenesis of Brain Abscesses I

Brain abscesses occur at focal points of bacterial multiplication within the brain parenchyma; they begin as a localised area of cerebritis and later progress into a collection of pus surrounded by a vascularised capsule.

By virtue of the impermeability of the blood-brain barrier, the brain parenchyma is relatively resistant to the establishment of focal bacterial infection. An area of necrosis caused by for example micro-infarction or hypoxaemia is necessary to act as a nidus for bacterial multiplication.

Several stages of development en route to the formation of a mature encapsulated brain abscess following bacterial ingress have been defined by neuroimaging studies

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THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

Stages of Development and Pathogenesis of Brain Abscesses II1. Early CerebritisDays 1-3: Perivascular inflammation, characterised by neutrophil infiltration, occurs around the site of focal infection with a surrounding area of oedema.

2. Late CerebritisDays 4-9: A central area of necrosis develops as the surrounding oedema progresses. Peripheral accumulation of fibroblasts preludes the development of a capsule.

3. Early CapsuleDays 10-14: Establishment of a ring-enhancing capsule of well-vascularised tissue with further fibroblast migration and adjacent reactive astrocytosis.

4. Late CapsuleDay 14 and beyond: Collagen fibre and granulation tissue deposition leads to a thickening of the capsule effectively walling off the area of focal suppurative infection.

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THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

Intracranial Infection I

To establish intracranial infection, bacteria reach the brain via three main routes:

1. Extension from a contiguous focus of infection, typically the middle ear or paranasal sinuses

2. Haematogenous (metastatic) spread from a distant extracranial source

3. Direct inoculation following neurosurgery or penetrating trauma

However in up to 30% of cases of brain abscess, the route of infection cannot be determined.

Suppurative intracranial infection can also manifest as subdural empyema, in which pus collects between the dura and arachnoid mater, and less frequently as extradural abscess, in which pus accumulates in the potential space between the inner skull table and dura mater. These conditions share a common aetiological basis with brain abscess and may occur concurrently.

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THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

Intracranial Infection II

Brain abscess is the most common pattern of intracranial suppurative infection

Page 8: The Diagnosis and Management of Brain Abscesses

THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

Spectrum of Pathogens Implicated in the Aetiology of Brain Abscess I

An understanding of the aetiology of brain abscess is important, since the primary source of infection not only correlates with the location of abscesses within the brain and hence their clinical features, but also the potential spectrum of causative organisms and thus informs the choice of antimicrobial treatment regimens.

The following pages will summarise the typical spectrum of causative pathogens divided by source of infection. Initial empirical antimicrobials treatment regimens are also suggested.

Scanning Electron Micrograph of Staphylococcus epidermidis

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THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

Spectrum of Pathogens Implicated in the Aetiology of Brain Abscess IIOtogentic and Paranasal Sinus

Brain abscesses secondary to ear infections are diminishing in frequency in developed countries as a result of the widespread use of early antimicrobial treatment for suppurative otitis media. Otogenic infection remains a frequent cause of brain abscess in the developing world.

Brain abscess complicating paranasal sinus infection is most commonly seen in young men. Subdural empyema is particularly associated with this route of infection.

Page 10: The Diagnosis and Management of Brain Abscesses

THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

Spectrum of Pathogens Implicated in the Aetiology of Brain Abscess IIIHaematogenous

*Additional anti-staphylococcal cover with e.g. vancomycin is recommended for presumed endocarditis-related brain abscess**Bronchiectasis, lung abscess and empyema are important causes of infection orginating in the respiratory tract

Haematogenous spread is now the most common route of infection.

Typically, multiple or multi-loculated abscesses are seen, occurring predominantly within the territory of the middle cerebral artery, often at the grey white matter interface where blood flow is most marginal.

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THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

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stigations• Management• Key Points• Summary• Self Assessment

Spectrum of Pathogens Implicated in the Aetiology of Brain Abscess IVHaematogenous Other Sources

Peridontal infections often give to rise polymicrobial infections.

Congenital heart disease complicated by a right to left shunt was a well recognised cause of brain abscess. Early diagnosis and operative repair of such lesions has seen a marked reduction in brain abscess attributable to this source.

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THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

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stigations• Management• Key Points• Summary• Self Assessment

Spectrum of Pathogens Implicated in the Aetiology of Brain Abscess VPenetrating Head Trauma and Postoperative

Penetrating head trauma such as gun shot wounds, open depressed skull fractures with foreign bodies in the brain parenchyma and basal skull fractures with CSF fistula can give rise to all forms of intracranial suppurative infection

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THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

Brain Abscesses in Immunosuppressed Patients IWhilst in immunocompetent individuals brain abscess are usually caused by pyogenic bacteria, in the immunosuppressed, a much broader array of organisms is implicated.

These include:

• Toxoplasma gondi (shown below)• Aspergillus species• Candida species• Nocardia• Mycobacterium tuberculosis

This is a high power view of brain in treated cerebral toxoplasmosis.

Immunocytochemical stain using a specific antibody to Toxoplasma gondii and the immunoperoxidase method – Wellcome Images.

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THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

Brain Abscesses in Immunosuppressed Patients II

• Histological/Microbiological diagnosisMoreover, in this patient group there is a high incidence of non-infective space occupying lesions such as lymphoma.

This highlights the particular importance of attempting to obtain histological and microbiological confirmation of diagnosis in these patients.

• HIVThere is an important caveat to this general principle for patients with advanced HIV infection.

Here, toxoplasmosis is the likely cause of abscess-like lesions and empirical therapy should be given for two weeks. If there is no clinical or radiological improvement, diagnostic aspiration should be performed.

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THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

Non-specific Nature of the Clinical Features of Brain Abscess

The presentation of brain abscess is variable and relates to the location, size and number of abscesses, the virulence of the infecting microorganisms and the immunological status of the affected individual.

Males are affected approximately twice as commonly as females; the median age is 30-45 years.

The clinical manifestations are nonspecific, meaning that diagnosis is often delayed. They relate predominantly to a rapidly expanding intracranial mass rather than an infective process.

Common presenting features are listed in the above table.

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THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

Investigation I

Neuroimaging

There is no single reliable confirmatory test for the diagnosis of brain abscess.

• Blood samplesLaboratory tests on blood samples are often unremarkable.

• NeuroimagingThe diagnosis rests heavily on suggestive neuroimaging findings in the individuals with a compatible clinical presentation.

The availability of neuroimaging techniques permitting detailed resolution of the brain parenchyma has had a profound impact on the management and outcome of brain abscess.

The appearance of brain abscesses varies significantly with their pathological stage, hence precise clinical correlation regarding the timing of scan with respect to the onset of symptoms is required.

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THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

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stigations• Management• Key Points• Summary• Self Assessment

Investigation II

A mature brain abscess appears as ring-enhancing lesions, for which there is a broad differential diagnosis.

Page 18: The Diagnosis and Management of Brain Abscesses

THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

MRI IThe appearances of brain abscess on MRI are similarly dependent upon their stage of evolution.

• T1-weighted ImagesEarly cerebral abscesses appear as a poorly-defined hypointense area relative to the normal brain parenchyma.

As the abscess matures, the hypointense area becomes better demarcated and the capsule becomes apparent as a slightly hyperintense rim.

Ring-enhancement following the administration of intravenous gadolinium is usually seen.

• T2-weighted ImagesA mature abscess has a hyperintense central area, corresponding to the pus-filled core, and a hypointense capsule and surrounding oedema.

CT is less sensitive than MRI for the detection of brain abscess, although it has the advantages of being quick and readily performed in even the most acutely unwell patients.

The changes produced by early brain abscess on CT are subtle and may easily be overlooked on non-contrast scans.

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THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

MRI IIEarly cerebritis appears as a focal area of low density that enhances following the administration of intravenous contrast medium.

As the abscess capsule matures, the classic appearance of a ring-enhancing lesion becomes more evident

MRI (T1+contrast) showing a small ring-enhancing lesion

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THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

Neuroimaging – Further considerationsNeuroimaging alone cannot with certainty distinguish brain abscess from other ring-enhancing lesions. Differentiating brain abscess and metastatic tumour is an important diagnostic challenge. Key features are listed below.

Interval scans have some utility in this setting; a rapidly expanding lesion favours a diagnosis of cerebral abscess. Newly developed techniques such as diffusion-weighted imaging and MR spectroscopy also show some promise in differentiating abscess from necrotic neoplasms and other cystic lesions.

Features suggestive of cerebral abscess:• Thin walled capsule• Thinning at the ventricular margin• Peripheral contrast enhancement

Features suggestive of metastatic tumour:

• Thickened, irregular and nodular capsule• Diffuse contrast enhancement

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THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

Microbiological InvestigationsChoosing appropriate antimicrobial therapy for brain abscess relies on accurate identification of the causal pathogen.

In all but exceptional circumstances, brain abscess material should be obtained for culture. With meticulous specimen handling, culture yields approach 100% for samples obtained prior to starting antimicrobials. Culture yields fall dramatically for specimens obtained after treatment has started. The Gram stain may, however, remain positive which alone may provide a useful guide to management.

When obtained, specimens should be cultured for aerobic and anaerobic bacteria, mycobacteria and fungi.Other clues to the likely causative pathogen may be obtained by culture of material from sites presumed to be the primary focus of infection (e.g. paranasal sinus).

CSF analysis, however, rarely provides any useful information and does not justify the substantial risk of brainstem herniation that lumbar puncture entails.

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thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

Brain Abscess Management IOverview

There are limited data from good quality clinical trials to guide the management of brain abscess and historically clinical practices have been diverse.

The main treatment strategies are:

• Antimicrobial agents• Needle aspiration - often using stereotactic guidance• Complete surgical excision

In addition, adjunctive therapies such as corticosteroids and anticonvulsant agents are variably used.

A combination of antimicrobial therapy and aspiration is now used for the majority of cases, with medical therapy alone and complete surgical excision reserved for particular circumstances.

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THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

Brain Abscess Management II.

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THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

Brain Abscess Management IIIAntimicrobial therapy

Effective antimicrobial therapy for brain abscess relies on identification of the causative microorganism allowing the selection of an appropriate regimen. Ideally, it therefore follows an aspiration procedure.

There are several important factors to consider in choosing an appropriate treatment regimen.

• Activity against implicated pathogens

Before culture information is available, the probable causative bacteria are predicted on the basis of the putative source of infection and the location of the abscess.

• Ability to penetrate abscess cavity

There is limited data available to guide practice.

Inferences are made from studies of CSF antimicrobial concentrations in the treatment of bacteria meningitis, although the characteristics of the blood-brain and blood-CSF barrier are known to differ.

.

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THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

Brain Abscess Management IV

• Duration and route of treatment Lone medical management

Medical management alone is sometimes used in patients who are regarded as poor candidates for surgery. It is preferable if the causative pathogen can be inferred from results of positive cultures from primary sites of infection, otherwise an empirical regimen is selected.

It may also be considered for…

• Multiple small abscesses• Abscesses located in surgically unaccessible or eloquent areas

It is most likely to be successful if…

• Abscesses are small (i.e. <1.5cm)• In cerebritis stage• Located in a well vascularised cortical area

Frequent interval scans should be performed to assess therapeutic response and to identify complications requiring definitive surgical management.

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THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

Brain Abscess Management V

• Duration and route of treatment Corticosteroids

Adjuvant corticosteroids are often used to reduce vasogenic oedema associated with brain abscesses.

There are important concerns regarding steroid use…

• Effectiveness in reducing oedema and mass effect not established in human clinical trials

• May retard abscess capsule development• May reduce antimicrobial penetration• Give false impression of a therapeutic response by reducing

ring-enhancement on follow-up scans

Most authors recommend that corticosteroids are reserved for situations of raised intracranial pressure resulting in a clear risk of brainstem herniation or other significant neurological deficit.

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THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

Brain Abscess Management VI

• Duration and route of treatment Anticonvulsants

Seizures are a frequent complication of brain abscess both in the acute setting and for a prolonged period after the resolution of the acute infection.

Some advocate the use of seizure prophylaxis for extended periods in every case of brain abscess, although there are again few good data.

If commenced, anticonvulsants should probably be continued for 6-12 months and then only withdrawn if the patient is seizure-free, the EEG normal and no signs of on going inflammation on neuroimaging.

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thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

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g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

Brain Abscess Management VII

Surgical

Surgical techniques for the management of brain abscess have evolved significantly in recent years.

Whilst debate still continues as to the best approach in particular situations, minimally-invasive aspiration and closed-drainage procedures have largely replaced craniotomy and attempted excision as the first line strategy.

Aspiration is not considered appropriate in all cases of brain abscess. Circumstances when excision may be the preferred initial surgical option are listed in the table on the next slide.

The most effective strategy for abscesses that do not improve or recur following attempted aspiration is not established. Repeated aspiration may be attempted, sometimes with the placement of a catheter to allow on going drainage and instillation of intracavity antimicrobials.

Alternatively complete surgical excision is undertaken.

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Brain Abscess Management VIII

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Brain Abscess Management IXAdjunctive therapies

As described in the introduction, advanced neurosurgical practices and potent antimicrobial agents, supported by modern neuroimaging technologies, have reduced mortality from brain abscess from being nearly universal to current levels of around 10%.

However, significantly decreased level of consciousness at presentation remains a poor prognostic indicator. In one series, 62% of patients with a GCS of <9 either died or fell into a permanent vegetative state.

Major sequelae such as seizures, focal neurological deficit and cognitive impairment are common in survivors.

• Seizures occur in up to 50% of patients and may have a latent period as long as 5 years.

• Focal neurological deficit occur in 25-50%.

• Significant cognitive impairment occurs in 20% of survivors, although is probably underreported.

Recurrence rates of between 10-50% have been reported. Surveillance is recommended for at least 1 year

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thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

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stigations• Management• Key Points• Summary• Self Assessment

Key Points• Brain abscesses are relatively uncommon and mortality is now

around 10%. However, significant attributable morbidity still occurs in affected individuals.

• Focal multiplication of bacteria at sites of parenchymal damage (often microscopic) lead to the formation of brain abscess.

• Bacteria reach the brain parenchyma via spread from a contiguous skull-vault infection, haematogenous spread from a distant site or direct inoculation following trauma or surgery.

• In immunocompetent individuals, abscesses are caused by a broad but often predictable array of bacterial pathogens.

• The clinical features are nonspecific and relate mainly to an expanding intracranial mass rather than an infective process.

• Modern neuroimaging techniques have dramatically improved our ability to detect brain abscesses, but microbiological confirmation is vital for directing treatment.

• Most brain abscesses can be managed with a combination of surgical aspiration followed by appropriate antimicrobial therapy

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THE DIAGNOSIS AND MANAGEMENT OF BRAIN ABSCESSES• Learning Objectives• Introduction• Development and Pa

thogenesis• Intracranial Infection• Pathogen Spectrum• Immunosuppressed

Patients• Clinical Features• Investigation• MRI• Further Neuroimagin

g • Microbiological Inve

stigations• Management• Key Points• Summary• Self Assessment

SummaryHaving completed this session you will now be able to:• Describe the stages of development and pathogenesis of brain

abscesses• Identify the typical spectrum of pathogens implicated in the aetiology

of brain abscess• Define the nonspecific nature of the clinical features of brain abscess• List the appropriate investigation of possible brain abscess and to

identify the important radiological features on CT and MR scanning• Develop a management plan for patients with brain abscess,

including antimicrobial treatment, surgical interventions and adjunctive therapies

References1. Mathisen GE, Johnson JP. Brain abscess. Clin Infect Dis 1997;25:763-

81.2. Solomon T. Intracranial space occupying infections and neurological HIV

disease. In: Donaghy M (Eds). Brain's Diseases of the Nervous System - 12th Edition. Oxford University Press, USA; 2009.

3. Lu C-H, Chang W-N, Lui C-C. Strategies for the management of bacterial abscess. J Clin Neurosci 2006;13:979-985.

4. Erdogan E, Cansever T. Pyogenic brain abscess. Neurosurg Focus 2008;24:1-10.

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Self AssessmentQuestion 1

After how many days following initial bacterial ingress does ring-enhancement typically first become evident on neuroimaging studies?

A. Less than 3 daysB. 4-7 daysC. 7-11 daysD. 11-14 daysE. More than 14 days

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Liverpool Medical Institution, UK Provisional date: May 2013

NeuroID 2013: Liverpool Neurological Infectious Diseases Course

Ever struggled with a patient with meningitis or encephalitis, and not known quite what to do?Then the Liverpool Neurological infectious Diseases Course is for you!

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Convenors: Prof Tom Solomon, Dr Enitan Carrol, Dr Rachel Kneen, Dr Nick Beeching, Dr Benedict Michael

Feedback from previous course:“Would unreservedly recommend to others” “An excellent 2 days!! The best course for a long time”