In our continuing discussion of
central nervous system infections,
we turn now to brain abscess.
50% of cases are due to
contiguous suppurative spread.
In other words, there's a focus
of pus somewhere near the brain.
For example, from osteomyelitis of
the frontal sinus or the sphenoid sinus.
Trauma accounts for about 10% of the cases,
which allow organisms direct access via a skull fracture.
And I want to tell you about an interesting patient I saw
that was involved on a baseball team
and one of his jobs was helping
to clean up the baseball diamond.
And he had a small electric
cart that he was driving around
that had some utensils like rakes on it
to rake up the grass and rake up the dirt
and he tried to drive that
cart through a narrow gate.
And when he did that,
it set the rake up into the air
flipping end over end and the rake –
the tines of the rake impaled
him in the side of the head,
penetrated his skull bone and gave
him a brain abscess due to soil born organism.
I thought that was an extremely strange and interesting occurrence.
But trauma is responsible for about 10% of the cases.
25% of the cases are the result of organisms –
microorganisms getting into the
bloodstream from another focus.
Say, from infective endocarditis.
And by the way,
if somebody has a brain abscess
due to an organism that is a common cause of endocarditis,
a careful evaluation for endocarditis should be done.
Lung abscess can also be responsible for
bacteria getting into the bloodstream
and alighting in the
brain HIV and IV drug use.
15% of the cases,
we’re not exactly
sure how the organisms got to the brain.
Bacteria are by far the most
common causes of brain abscess
and frequently involve other streptococci
which colonize mucosal surfaces.
And these are normal flora.
But because the mucosal surfaces
also are teeming with other organisms,
you would expect mixed
infections in a lot of patients.
Staph aureus is responsible for
about 10 to 20% of brain abscesses
and these are usually not large brain abscesses.
I think I have mentioned
in other presentations that
life on human beings is predominantly anaerobic,
especially on mucosal surfaces
where anaerobes outnumber the
aerobes from 10 to 1 to 1000 to 1.
And here's an example of Prevotella,
which is an anaerobic organism,
gram-negative rod that you find
frequently in the oropharynx.
Nocardia is a soil-born organism,
but you particularly can encounter this organism
who don't handle it well in
So, it may get into the lungs
patients and from there disseminate.
And what you're seeing in this particular slide
is a very filamentous,
acid fast rod of Nocardia.
Fungi can cause brain abscess
and the ones that cause
it most commonly are these,
And what you're seeing in this
particular view is an elongate bud,
which is called a pseudohypha
with yeast budding from it.
Classic for Candida.
Aspergillus is a filamentous organism.
And what you should notice about
this particular organism is that it
tends to look like it's flowing
in one direction and that's
because the organisms as they divide,
one trunk divides into two,
so-called dichotomous branching,
and that's why the organisms in a
tissue section appear to be flowing.
And Aspergillus accounts for 10% to 20%
of all cases of invasive brain abscesses.
one of the bread molds,
is also responsible for brain abscess
and it’s usually in a person with ketoacidosis.
And the classic,
is a diabetic in ketoacidosis.
And there are other bread molds,
but the spores from these bread molds are ubiquitous.
All of us inhale them daily,
but we have
a normal immune system and
we do not have ketoacidosis.
If you provide an acidic environment,
these organisms can invade blood vessels.
Scedosporium apiospermum is an organism
that you frequently find in freshwater.
And that's why it has an association
not only with neutropenia,
but with near-drowning accidents.
I'm familiar with a patient I saw
in a boat that apparently capsized
and he was essentially submerged
head first in mud at the bottom of a river.
And he developed a Scedosporium brain abscess.
This organism is also known as
and we actually sent out some investigators
from the University of Georgia to culture
the silt at the bottom of this river.
And sure enough,
we isolated this organism from the riverbed.
But the association of
near-drowning is an important factor
if somebody develops
this kind of a brain abscess.
And then the classic endemic fungi,
And what you're seeing in this
particular picture is a macrophage
that is stuffed full of
these little tiny budding yeast.
I think you can see that
they appear to have a capsule around them.
They don't really –
that's an artifact of the staining,
but that's where the name
came from, Histoplasma capsulatum.
And the filamentous form of the organism
a mold that you find in the
Ohio and Mississippi River valleys.
Coccidioides immitis is also a mold that
you find in the desert Southwest,
areas like the San Joaquin Valley in California.
The soil is actually teeming with some of these fungi.
And you inhale the tiny arthroconidia
and when it gets into the lungs
at 37°, it becomes this huge spherical structure
called a spherule.
And this certainly can cause brain abscess
in this endemic area,
especially among immunocompromised individuals.
Not terribly common as a cause of brain abscess,
but more of skin infections is Blastomyces dermatitidis.
And this is characterized by
these very large budding yeast
and with broad-based buds.
The way I remember it is B for blasto
B for broad-based budding yeast,
if you want to get alliterative about it.
And then parasites can cause brain abscess.
Among the most common would be protozoa,
specifically Toxoplasma gondii and this
is acquired by ingesting rare or raw meat.
And just as an aside,
if you and I were to go out for a steak dinner,
my steak would look like
Joe DiMaggio's baseball glove
from the 38 World Series.
It is dark and hard
as about 25% of raw meat contains
living protozoa of Toxoplasma gondii.
So, I'm not eating that stuff.
You may like it rare,
but I choose not
to eat rare meat.
And it’s particularly problem in patients
with HIV infection with depressed immunity.
And when their CD4 count gets less than 100,
they are very susceptible to Toxoplasma
encephalitis and brain abscess.
And so are patients who have
Chagas disease that you find in
South America and Central America.
Entamoeba histolytica, also found in
normally causes gastroenteritis
and maybe a liver abscess,
but every once in a while
a brain abscess.
also associated with
swimming in freshwater
would be the free living amoeba that
belong to the Naegleria and Acanthamoeba species.
So, swimming and diving, particularly diving,
in freshwater rivers,
ponds and lakes,
free living amoeba.
And you can see these large
in the brain parenchyma
in this particular image.
Worms can also do it.
Among the most common would be
the pork tapeworm Taenia solium.
Not the beef tapeworm so much.
The pork tapeworm seems to
cause a disorder in humans called cysticercosis,
whereas the beef tapeworm doesn't
usually cause that disease in human beings.
And you get this cysticercosis
by ingesting the egg from
one of these worms,
from contaminated food or water.
can certainly cause abscess anywhere
and the worms can migrate anywhere
via the bloodstream
and every once in a while will be
the cause of the brain abscess.
I've never seen a patient with a Schistosoma brain abscess.
And this is also
acquired by wading or swimming
in freshwater in developing countries.
Also found in the Far East is Paragonimus,
which is from the consumption of freshwater crustaceans,
once again something you won't find me ingesting.