Transcript Brain abscess - howMed Lectures

Brain abscess
• Brain abscess (or cerebral abscess) is an
abscess caused by inflammation and collection
of infected material within the brain tissue.,
coming from
• local (ear infection, dental abscess, infection of
paranasal sinuses, infection of the mastoid air
cells of the temporal bone, epidural abscess)
• or remote (lung, heart, kidney etc.) infectious
sources,
• The infection may also be introduced through a
skull fracture following a head trauma or surgical
procedures.
• Brain abscess is usually associated with
congenital heart disease in young children. It
may occur at any age but is most frequent in the
3rd third decade of life.
• Deadly brain abscesses due to infection caused
from tongue piercing have occurred
Features
• The symptoms of brain abscess are caused by a
combination of
• increased intracranial pressure due to a spaceoccupying lesion (headache, vomiting, confusion, coma),
• infection (fever, fatigue etc.) and
• focal neurologic brain tissue damage (hemiparesis,
aphasia etc.).
• The most frequent presenting symptoms are
• headache, drowsiness, confusion, seizures, hemiparesis
or speech difficulties together with fever with a rapidly
progressive course.
Features
• The symptoms and findings depend largely on
the specific location of the abscess in the brain.
• An abscess in the cerebellum, for instance, may
cause additional complaints as a result of brain
stem compression and hydrocephalus.
• Neurological examination may reveal a stiff neck
in occasional cases (erroneously suggesting
meningitis).
• The famous triad of fever, headache and focal
neurologic findings are highly suggestive of
brain abscess.
• Many brain abscesses are polymicrobical. The
predominant organisms include:
• Staphylococcus aureus,
• aerobic and anaerobic streptococci (especially
Streptococcus intermedius),
• Bacteroides, Prevotella, and Fusobacterium
species, Enterobacteriaceae, Pseudomonas
species, and other anaerobes.
• Less common organisms include: Haemophillus
influenzae, Streptococcus pneumoniae and
Neisseria meningitides.[
• Bacterial abscesses rarely (if ever) arise
de novo within the brain, although
establishing a cause can be difficult in
many cases.
• There is almost always a primary
lesion elsewhere in the body that must be
sought assiduously, because failure to
treat the primary lesion will result in
relapse.
location of the primary lesion
• for example in compound skull fractures where
fragments of bone are pushed into the substance of the
brain, the cause of the abscess is obvious. Similarly,
bullets and other foreign bodies may become sources of
infection if left in place.
• The location of the primary lesion may be suggested by
the location of the abscess:
• infections of the middle ear result in lesions in the middle
and posterior cranial fossae;
• congenital heart disease with right-to-left shunts often
result in abscesses in the distribution of the middle
cerebral artery;
• and infection of the frontal and ethmoid sinuses usually
results in collection in the subdural sinuses.
predisposing conditions:
• Sinus and dental infections— streptococci, anaerobic GNR (e.g.
Prevotella, Porphyromonas, Bacteroides), Fusobacterium, S.
aureus, and Enterobacteriaceae
• Penetrating trauma—S. aureus, aerobic streptococci,
Enterobacteriaceae, and Clostridium spp.
• Pulmonary infections— streptococci, anaerobic GNR (e.g.
Prevotella, Porphyromonas, Bacteroides), Fusobacterium,
Actinomyces, and Nocardia
• Congenital heart disease—Aerobic and microaerophilic streptococci,
and S. aureus
• HIV infection—T. gondii, Mycobacterium, Nocardia, Cryptococcus,
and Listeria monocytogenes
• Transplantation—Aspergillus, Candida, Cryptococcus, Mucorales,
Nocardia, and T. gondii
• Neutropenia—Aerobic GNR, Aspergillus, Candida, and Mucorales
• Protozoa
– Toxoplasma gondii
– Entamoeba histolytica,
– Trypanosoma cruzi,
– Schistosoma,
– Paragonimus, &
• Helminths
– Taenia solium
DIAGNOSIS
• The diagnosis is established by a computed tomography
(CT) (with contrast) examination.
• At the initial phase of the inflammation (which is referred
to as cerebritis), the immature lesion does not have a
capsule and it may be difficult to distinguish it from other
space-occupying lesions or infarcts of the brain.
• Within 4–5 days the inflammation & dead brain tissue
are surrounded with a capsule, which gives the lesion
the famous ring-enhancing lesion appearance on CT
examination with contrast (since intravenously applied
contrast material can not pass through the capsule, it is
collected around the lesion and looks as a ring
surrounding the relatively dark lesion).
DIAGNOSIS
• Ring enhancement may also be observed in
cerebral hemorrhages and some brain tumors.
• However, in the presence of the
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–
–
–
rapidly progressive course with
fever,
focal neurologic findings (hemiparesis, aphasia) &
signs of increased intracranial pressure, the most
likely diagnosis should be the brain abscess.
Lumbar puncture
• procedure, which is performed in many
infectious disorders of the central
nervous system is contraindicated in this
condition (as it is in all space-occupying
lesions of the brain) because removing a
certain portion of the CSF may alter the
ICP balances and causes the brain tissue
to move across structures within the skull
(brain herniation)
Treatment
• The treatment includes
• lowering the increased intracranial
pressure &
• starting intravenous antibiotics (and
meanwhile identifying the causative
organism mainly by blood culture studies)
Treatment
• Surgical drainage of the abscess remains
part of the standard management of
bacterial brain abscesses.
• The location and treatment of the primary
lesion also crucial, as is the removal of
any foreign material (bone, dirt, bullets,
and so forth).
For Surgical drainage here are few
exceptions
• Haemophilus influenzae meningitis is often
associated with subdural effusions that are
mistaken for subdural empyemas. These
effusions resolve with antibiotics and require no
surgical treatment.
• Tuberculosis can produce brain abscesses that
look identical to conventional bacterial
abscesses on CT imaging. Surgical drainage or
aspiration is often necessary to identify
Mycobacterium tuberculosis, but once the
diagnosis is made no further surgical
intervention is necessary.
Prognosis
• It was once fatal before the CT era, now,
• if the abscess is treated before the person goes into a
coma, then the death rate has been estimated from 5%
to 20%
• although it is greater in cases of multiple abscesses,
when raised intracranial pressure is observed and
depending on the level of neurological dysfunction on
presentation.
• Early treatment and the patients overall health has an
effect on prognosis.
• Other factors include:
– antibiotic resistance or
– the abscess location. An abscess deep within the brain is more
difficult to treat than others.
nocardial brain abscess (arrows)
a)represent the abscess contents, the middle zone (b) formed by proliferating
fibroblasts resembling a fibrocollageous capsule &
outermost one (c) formed by gliotic and inflammed brain parenchyma
S. anginosus group is commonly
isolated from brain abscesses
Brain abscess, showing fungal
hyphae in cavity