00:02
Now, when somebody comes in
with altered mental status
and signs of encephalitis,
we certainly are going to examine
the cerebrospinal fluid if it's safe.
00:13
And so, what we’re going to look for is the cytology.
00:16
And what you would expect,
unlike bacterial meningitis,
is a lymphocytic pleocytosis.
00:24
There may be some neutrophils there, but
there is a predominance of mononuclear cells.
00:30
Unlike bacterial meningitis,
your glucose is normally not low.
00:38
The protein may be elevated.
00:42
Those are the classic findings, but the
exceptions to the rule are the West Nile virus,
which may have more neutrophils in it
and Eastern equine encephalitis
may have a neutrophil predominance.
00:57
And the cell count is going to be 50 to 500 cells.
01:03
To make a specific diagnosis, we have
to rely on PCR and antibody studies.
01:10
The herpes simplex PCR is very sensitive
and very specific and we use it all the time.
01:19
For varicella zoster,
it's not nearly so sensitive,
but it does have a high specificity.
01:25
Culturing these viruses is not particularly useful.
01:32
So, serology is important
and we’re going to get an
acute serum on admission
and then periodically get convalescence serum,
looking for antibody rises.
01:46
We can do PCR on gastrointestinal samples,
respiratory secretions and skin vesicles
and they're pretty sensitive and specific.
01:55
But if we just can't figure out
why the patient has encephalitis
and the patient is deteriorating,
then we may need to resort to a brain biopsy.
02:07
These are usually done through a
burr hole and a needle aspirate.
02:17
Neuroimaging is important in
patients who have encephalitis
and the MRI is the study of choice.
02:24
And particularly, in herpes simplex virus,
90% of the time you're going to
be looking in the temporal lobes.
02:34
Varicella zoster produces multifocal hemorrhage and infarction
and a West Nile virus has less frequent
abnormalities than herpes simplex virus.
02:50
We don't do EEG very often,
but if you were to do it,
you'd find generalized slowing
in most forms of encephalitis.
02:59
And in herpes, you’d find,
once again, abnormalities
like spikes in the temporal lobe.
03:07
And you’d find that in a majority of
patients with herpes virus encephalitis.
03:14
And this, for example,
is what herpes virus encephalitis looks like.
03:19
Notice the predominance in both
temporal lobes in this patient.
03:25
Notice the multifocal location in the
patient with varicella zoster encephalitis.
03:32
And notice that in West Nile virus,
the encephalitis is highlighted by
increased signal in the basal ganglia.
03:41
And remember, we talked about parkinsonism,
and so that fits with West Nile virus.
03:50
The enteroviral encephalitis,
you can have increased
signal in both hemispheres.