1. Dr. Joe M Das
Senior Resident
Dept. of Neurosurgery
Brain abscess
2. History
Definition
Epidemiology
Pathogenesis
Clinical features
Investigations
Treatment
Special abscesses
3. History
Hippocrates – Purulent otorrhea and delerium
The first successful operation for brain abscess - S.F. Morand
(France) in 1752 on a temperoethmoidal abscess.
“Pyogenic Disease of the Brain and Spinal Cord, Meningitis,
Abscess of the Brain, Infective SinusThrombosis” (1893) -
William Macewen – Father of modern day abscess management
King (1924) – marsupialization
Dandy (1926) – aspiration
Sargent (1928) – enucleation
Vincent (1936) – complete excision
Heineman et al (1971) – successful medical management
4. Henry II, King of France
Death was predicted by
Nostradamus
Died from an orbital wound
The skull was not penetrated
but infection spread
intracranially
Infection had spread to the
brain along the orbital veins,
forming an abscess under the
cortex.
6. Definition
Mathisen GE, Johnson JP: Brain abscess. Clin Infect Dis
1997; 25:763-781.
A focal intracranial
infection that is initiated as
an area of cerebritis and
evolves into a collection of
pus surrounded by a
vascularized capsule.
7. Epidemiology
1500-2500 cases per year in the US
8% of ICSOL in developing countries
♂: ♀ = 2-3 : 1
Median age – 30 – 40 yrs
2° to otitic focus - <20 / > 40 yrs
2° to PNS infection – 30-40 yrs
25% in children – otitic focus / CHD
0.2% of cranial operations
Immunosuppression
9. Contiguous spread
Routes of contiguous spread:
Direct extension through osteitis / osteomyelitis
Retrograde thrombophlebitis via diploic or emissary vein
Via local lymphatics
Localisation:
Otitis media –Temporal lobe / cerebellum
PNS – Frontal lobe
Sphenoid sinusitis –Temporal lobe / sella
Dental infection (molars) – Frontal lobe (M.C) / temporal
10. India – M.C source –
Middle ear suppuration
Western countries – M.C
source – Spread from PNS
Sites of bone dehiscence:
Post wall of frontal sinus
Tegmen tympani
Trautmann’s triangle
11. Hematogenous
Multiple, multiloculated abscesses - ↑ mortality
M.C sources in adults – chronic pyogenic lung diseases (especially
lung abscess), bronchiectasis, empyema, and CF.
Distant sources – wound & skin infections, osteomyelitis, pelvic
intra-abdominal infections; after esophageal dilation or sclerosing
therapy for esophageal varices.
CCHD (TOF/TGV) – 5-15% of brain abscess cases.
<5% of patients with IE despite the presence of continuous
bacteremia
Hereditary hemorrhagic telangiectasia (with coexisting pulmonary
AVM) - allows septic emboli to cross the pulmonary circulation
without capillary filtration – 5-9% risk
12. How does TOF lead to brain abscess?
TOF Chronic hypoxemia Polycythemia
↑ viscosity Multiple infarcts at grey-white
junction Milieu for bacterial growth
13. Trauma
Open cranial fracture with dural breach / foreign body
injury / as a sequel of neurosurgery
Civilian population - 2.5-10.9 %
Includes those 2° to compound depressed skull
fractures, dog bites, rooster pecking, tongue piercing
Nosocomial brain abscess - halo pin insertion, electrode
insertion to localize seizure foci, and in malignant glioma
patients treated by placement of Gliadel wafers
14. In military populations - 3-17 %
Usually occur secondary to retained bone fragments or
contamination of initially uninfected missile sites with
bacteria from skin, clothes, or the environment
The retained foreign bodies did not seem to increase the
infection rate except in patients who suffered an in-
driven cluster of bone fragments or leakage of
cerebrospinal fluid.
19. Recommended Dosages of Antimicrobial
Agents in Adults with Brain Abscess and
Normal Renal and Hepatic Function
20. Stages of abscess formation
A canine model after inoculation of α-hemolytic Streptococci
Britt RH, Enzmann DR,YeagerAS. Neuropathological and computerized tomographic findings
in experimental brain abscess. J Neurosurg. 1981 Oct;55(4):590-603.
24. Histopathologic findings in the stages
of brain abscess formation
Data from Tunkel AR, Scheld WM. Pathogenesis and pathophysiology of bacterial infections. In: Scheld WM, Whitley RJ, Durack, DT, eds. Infections of the Central
Nervous System, tind ed. Philadelphia: Lippincott-Raven; 1997;297-312; and Britt RH, Enzmann DR, Yeager AS. Neuropathological and computerized tomographic findings in
experimental brain abscess. J Neurosurg. 1981;55:590-603.
25. Early cerebritis
Acute inflammatory
infiltrate
Marked edema
Invisible on CT OR
Poorly marginated cortical
/subcortical hypodensity
with mass effect with no
enhancement
26. Late cerebritis
Central necrosis
Macrophages and
fibroblasts
Vascular proliferation
Maximum edema
Irregular rim enhancing
lesion with
hypodense center, better
defined than early
cerebritis
27. Early capsule formation
Necrotic centre ↓
Collagenous capsule
Edema starts to regress
Well-defined rim
enhancing mass; an outer
hypodense and inner
hyperdense rim (double
rim sign)
28. Late capsule formation
Collagen capsule complete
↑ density and thickness
Rim enhancing lesion with
thickened capsule and
diminished hypodense
central cavity
31. Why does abscess often rupture
intraventricularly?
Difference in vascularity between cortical grey
and white matter
↑ fibroblast proliferation on cortical side
Capsule less formed on ventricular surface
Tendency for intraventricular rupture
33. Initial Findings in Patients with Brain
Abscess Based on Intracranial Location
Frontal >Temporal >
Parietal > Cerebellum >
Occipital
34. Classic triad of headache, fever, and focal neurologic
deficit is rarely seen (< 5-20% of cases in case series)
1/3rd – polymicrobial
Incidence of negative cultures - 25-30%
Sudden worsening of a preexisting headache
accompanied with meningismus may be indicative of a
catastrophic event—rupture of the abscess into the
ventricular space.
35. When there is no obvious source (up to 25% of cases),
upper respiratory tract flora and anaerobes are often
isolated.
Several sources have identified a patent foramen ovale by
echocardiogram in these cases and propose this as a
possible mechanism for seeding oral flora to the brain.
Khouzam RN, El-DoklaAM, Menkes DL. Undiagnosed patent foramen ovale
presenting as a cryptogenic brain abscess: case report and review of the literature. Heart
Lung. Mar-Apr 2006;35(2):108-11.
36. Investigations
X-ray skull:
Often normal
Post-traumatic – air inside cranial cavity
Sinusitis/mastoiditis
CT brain:
Diagnosis, localisation and treatment
Sinisitis/mastoiditis
Staging, HCP, ↑ICP, edema, associated subdural empyema,
meningitis, ventriculitis, multiplicity
NCCT - Isodense / hyperdense
CECT - Smooth, thin, regular wall with decreased density both
in the centre and surrounding
37. MRI Brain
T1
Central low intensity (hyperintense to CSF)
Peripheral low intensity (vasogenic oedema)
Ring enhancement
Ventriculitis may be present, in which case hydrocephalus will commonly
also be seen
T2 / FLAIR
Central high intensity (hypointense to CSF, does not attenuate on FLAIR)
Peripheral high intensity (vasogenic oedema)
The abscess capsule may be visible as a intermediate to slightly low signal
thin rim
DWI / ADC
High DWI signal is usually present centrally
Low signal onADC
38. SWI
Low intensity rim
Complete in 75%
Smooth in 90%
Mostly overlaps with contrast enhancing rim
Dual rim sign - a hyperintense line located inside the low intensity
rim
MR perfusion - RCBV is reduced in the surrounding oedema
c.f. to both normal white matter and tumour oedema seen in high
grade gliomas
MR spectroscopy - elevation of a succinate peak is relatively
specific but not present in all abscesses ; high lactate,
acetate, alanine, valine, leucine, and isoleucine levels peak may be
present ; cho / crn and NAA peaks are reduced
49. Surgical therapy
The optimal approach to patients with bacterial brain abscess
Aspiration after bur-hole placement or complete excision after
craniotomy (no prospective trial comparing these two)
May be performed under stereotactic neuroimaging guidance
Stereotactic aspiration is a useful approach even for abscesses
located in eloquent or inaccessible regions; repeat aspiration
should be considered if the initial aspiration proves ineffective or
partially effective.
Intraoperative ultrasound - for the aspiration of small abscesses
and can delineate abscess pockets,
Recurrence rates after stereotactic aspiration range from 0-24 %.
50. Pus has been aspirated. What all
investigations are to be sent?
A. Stains
A. Gram stain
B. Acid-fast stain (AFB stain) for Mycobacterium
C. Modified acid-fast stain (for Nocardia) looking for branching acid
fast bacillus
D. Special fungal stains (e.g., methenamine silver, mucicarmine)
B. Cultures
A. Routine cultures: aerobic and anaerobic
B. Fungal culture: this is not only helpful for identifying fungal
infections, but since these cultures are kept for longer period and
any growth that occurs will be further characterized, fastidious or
indolent bacterial organisms may sometimes be identified
C. TB culture
51. What are the indications for initial
surgical treatment?
1. Significant mass effect exerted by lesion (on CT or MRI)
2. Difficulty in diagnosis (especially in adults)
3. Proximity to ventricle: indicates likelihood of intraventricular
rupture which is associated with poor outcome
4. Evidence of significantly increased intracranial pressure
5. Poor neurologic condition (patients responds only to pain, or
does not even response to pain)
6. Traumatic abscess associated with foreign material
7. Fungal abscess
8. Multiloculated abscess
9. Follow-up CT/MRI scans cannot be obtained every 1-2 weeks
52. What are the indications for complete
excision by craniotomy ?
Multiloculated abscesses in whom aspiration techniques have failed
Abscesses containing gas
Abscesses that fail to resolve
Posttraumatic abscesses that contain foreign bodies or retained
bone fragments to prevent recurrence
Abscesses that result from fistulous communications (e.g.,
secondary to trauma or congenital dermal sinuses)
Abscess localized to one lobe of the brain and contiguous with a
primary focus.
Cerebellar abscess in children
Difficulty in diagnosis
Suspected fungal abscess
53. What are the contraindications for
craniotomy and evacuation?
Abscess in the cerebritis stage
Deep-seated abscess in eloquent area
Multiple abscesses
54. Aspiration vs. Craniotomy
Craniotomy is now rarely practiced as the first line of treatment.
Aspiration repeated as necessary or with drainage, has widely replaced
attempts at complete excision.
Several reports have advocated excision as the procedure of choice
because it is often followed by a lower incidence of recurrence and
shorter hospitalization.
Xiao et al reported that favorable outcome was not significantly different
between the patients treated by excision or aspiration. However, the
mortality rate was significantly lower in the patients treated with
excision than the patients treated with aspiration.
This is probably due to the better general condition and/or more
favorable location of abscess that could be excised surgically in such
patients.
Stereotactic aspiration should be considered the treatment of choice in
all but the most superficial and the largest cerebral abscesses.
55. IV rupture with ventriculitis and HCP –
What to do?
Rapid evacuation and débridement of the abscess cavity via
urgent craniotomy
+
Ventricular drainage
+
Intravenous or intrathecal administration of appropriate
antimicrobial agents
56. When to opt for medical therapy alone?
Patients with medical conditions that increase the risk
associated with surgery
Multiple abscesses
Abscesses in a deep or dominant location
Coexisting meningitis or ependymitis
Early reduction of the abscess with clinical improvement
after antimicrobial therapy
Abscess size < 3 cm
57. What is the optimal duration of
medical treatment?
Bacterial brain abscess – 6-8 weeks IV → 2-3 months oral
antimicrobial therapy
Post-surgical excision - Courses of 3 to 4 weeks of antimicrobial
therapy
Medical therapy alone - up to 12 weeks with parenteral agents
A combination of surgical aspiration or removal of all abscesses
larger than 2.5 cm in diameter → 6 weeks or more of
antimicrobial therapy, and weekly neuroimaging to document
abscess resolution
Repeat neuroimaging studies - biweekly for up to 3 months after
completion of therapy
58. How will you follow up an abscess case
radiographically?
CT scans weekly during the course of therapy
One week after discontinuation of antibiotics
Scan one month later
Monthly or bimonthly till radiographic resolution
Time course for abscess resolution:
↓ in abscess size – 2-3 weeks after initiating therapy
Complete resolution of abscess cavity, mass effect – 3-4 months
Residual contrast enhancement – 6-9 months
60. Any role for steroids?
↓ host defense mechanisms and ↓ penetration of some antimicrobial
agents into the brain abscess cavity
May result in improvement of neurological symptoms and signs.
Therapy started in abscess patients with:
Associated edema and mass effect
Progressive neurological deterioration
Impending cerebral herniation.
Dose:
Dexamethasone, 10 mg every 6 hours is generally administered initially
and then tapered once the patient has stabilized.
The use of prolonged courses of corticosteroids is discouraged.
May also decrease contrast enhancement of the abscess capsule in the
early stages of infection, thereby being a false indicator of radiologic
improvement.
61. What is the role of anticonvulsants?
Initiated immediately and continued at least 1 year due to
high risk in the brain abscesses.
The treatment can be discontinued if no significant
epileptogenic activity can be shown in electroencephalogram
(EEG).
62. How to treat otogenic brain abscess?
Initial neurosurgical removal of abscess, which after
improvement of general condition of the patient should
be followed by radical otosurgical removal of the process
from the ear.
Otogenic brain abscess: diagnostic and treatment experience. D Djeric NArsovic V
Djukic. International Congress Series, 2003; 1240 (61-65)
Brain abscesses of otogenic origin. [Article in Serbian] NesićV1, Janosević L, Stojicić G,
Janosević L, Babac S, Sladoje R. SrpArh Celok Lek. 2002 Nov-Dec;130(11-12):389-93.
63. How to manage multiple brain
abscesses?
Incidence – 10-50%
Emergent stereotactic aspiration for all lesions > 2.5 cm diameter and
those causing mass effect, located deep in brain stem or close to
ventricular wall
If all the lesions are < 2.5 cm and not producing mass effect, the
largest one should be aspirated for diagnostic cultures.
Antibiotics withheld till culture results
Antibiotics for 3 months (Immunosuppressed – 1 yr)
Repeat surgical aspiration if
radiographic enlargement after 2 weeks of therapy
Failure to diminish in size after 4 weeks of antibiotics
Clinical deterioration
64. How to treat Nocardial brain abscess?
A sulfonamide ± trimethoprim, is recommended.
Alternative agents include minocycline,imipenem, amikacin, third-
generation cephalosporins, and linezolid
In immunocompromised patients or those in whom therapy fails
a third-generation cephalosporin or imipenem + a sulfonamide or
amikacin
Nocardia farcinica,a species that may be highly resistant to various
antimicrobial agents, successful treatment has included
moxifloxacin.
Craniotomy with total excision is difficult in patients with Nocardia
brain abscess because these abscesses are often multiloculated.
The duration of therapy - 3 to 12 months, but it should probably
be continued up to 1 year in those who are immunocompromised.
65. What are the treatment options for
fungal brain abscess?
Patients with fungal brain abscess, especially those who are
immunocompromised, have a high mortality rate despite
combined medical and surgical therapy.
Candidal brain abscess -Amphotericin B preparation + 5-
flucytosine
The therapy of choice for Aspergillus brain abscess is voriconazole.
Alternative agents include an amphotericin B preparation,
posaconazole, and itraconazole.
Itraconazole - as an extension of successful treatment rather than
as primary therapy.
Excisional surgery or drainage is a key factor in the successful
management of CNS aspergillosis.
66. CNS mucormycosis - Amphotericin B deoxycholate or a lipid
formulation of amphotericin
Correction of the underlying metabolic derangements and
aggressive surgical débridement
The etiologic agents of mucormycosis invade blood vessels,
tissue infarction occurs and impairs the delivery of antifungal
agents to the site of infection; this often leaves surgery as the
only modality that may effectively eliminate the infecting
microorganism.
In patients not responding to or intolerant of an
amphotericin B formulation, posaconazole can be used as
salvage therapy.
HBO - useful adjunct
Surgery is the cornerstone of therapy for brain abscesses
caused by Scedosporium species
Voriconazole is the agent of choice.
67. What is meant by delayed “glue
abscess”?
Delayed multiloculated abscess after embolization ofAVM
nidus
The duration of the procedure and repeated handling of the
catheters along with use of large amount foreign material or
Hysto-acryl “glue” can precipitate infection.
Cure of the lesion can only be obtained by surgical excision
of the infected and partially embolizedAVM.
Antibiotic prophylaxis with all endovascular procedures is
recommended
Mourier L, Bellec C, Lot G, Reizine D, Gelbert F, Dematons C, et al. Pyogenic parenchymatous and nidus infection after embolization
of an arteriovenous malformation: an unusual complication. Case report. Acta Neurochir (Wien) 1993;122:130-3.
Pendarkar H, KrishnamoorthyT, Purkayastha S, GuptaAK. Pyogenic cerebral abscess with discharging sinus complicating an
embolized arteriovenous malformation. J Neuroradiol 2006;33:133-8
68. What are the factors to be considered in a patient
with cyanotic heart disease developing a brain
abscess?
5-18% population with CHD. 10 times more prone. M.C –TOF
Intracardiac right to left shunt by-pass allows direct entry of blood
containing bacteria to the cerebral circulation without pulmonary
filtration.
Anaerobic streptococci (Sterile cultures are reported in 16-68%)
Cardiopulmonary risk, coagulation defects and variable degree of
immunodeficient states
A deeply located parieto-occipital abscess larger than 2 cm
diameter which causes mass effect, should be aspirated
immediately even in late cerebritits stage using stereotactic or CT
guided methods to decrease intra-cranial pressure and avoid
intraventricular rupture of brain abscess.
Intravenous Beta-lactam antibiotics are started immediately.
69. Cerebellar abscess
6-35% of all brain abscesses
Often ominously silent and carry significant mortality
Can cause sudden total occlusion of CSF pathways early in
the course of disease.
Presence of periventricular lucency is an absolute indication
of immediate ventricular drainage regardless of level of
consciousness i.e. even if patient is fully conscious.
Burr hole aspiration has emerged as a satisfactory method
70. Sequelae
30-50% of survivors are found to have neurological sequelae.
The incidence of residual neural deficits - hemiparesis,
cognitive and learning deficits in children, is less with
aspiration than excision.
About 72% of patients can have epileptic seizures upto five
years of diagnosis.This incidence is less with aspiration than
excision.
5 to 10% abscesses recur due to inadequate or inappropriate
antibiotics, failure of removal of foreign body, dural fistula or
failure of eradication of primary source.
Hydrocephalus may also develop
71. What is the difference between otogenic and odontogenic
brain abscess?
Unlike otogenic abscess, odontogenic abscess occurs as a
sequel of acute rather than chronic infection
What is the most common site of metastatic abscess?
In the distribution of MCA – Parietal & frontal (left side)
Grey-white junction – capillary flow slowest
Does a high velocity bullet injury cause an abscess?
The fragments do not present a significant risk because of
heat sterilisation and do not require removal
