We’re gonna be talking about meningitis and encephalitis.
Let’s get started by talking about some definitions.
So what does meningitis mean?
Meningitis is essentially inflammation of the membranes
surrounding the brain and spinal cord.
Here, we’re gonna be talking about
primarily infectious related meningitis.
Encephalitis is a little bit different
in a sense that it’s inflammation of the brain itself.
So meningitis is the inflammation of the membranes,
the meninges that surround the brain and the spinal cord.
And encephalitis is inflammation of the brain matter itself.
Now what causes meningitis?
The most common things we’re gonna talk about here.
So bacterial meningitis is one of them.
And the most common bacteria
that cause meningitis are streptococcus pneumoniae,
listeria monocytogenes and haemophilus influenza.
Important things about each of these,
these different bacteria.
So strep pneumo is a very common cause of bacterial meningitis.
Neisseria meningitidis is a very — is less common
but is unfortunately,
has a very high, high mortality rate associated with it.
An interesting thing about Neisseria
is that it’s related to patients
living in closed quarters
or the people living in closed quarters.
like dorms and military barracks are the classic patients
who we worry about this in.
Now for this reason is why patients or teenagers rather,
get a vaccination
or it's recommended they get a vaccination
against Neisseria meningitidis before they go off to college
or potentially to the military to help prevent Neisseria.
Listeria monocytogenes is a cause of meningitis
that’s primarily in the very young and the very old.
So in that new born,
infant time period as well as in elderly people,
you wanna think about listeria.
And then haemophilus influenza
used to be a very common cause of meningitis
but in the last number of years,
the use of haemophilus vaccination has increased quite a bit.
So haemophilus has decreased its rate
of causing meningitis significantly.
is a rare but potential cause for meningitis,
that’s meningitis caused by tuberculosis.
Viral meningitis is actually
a relatively common cause of meningitis.
The most common viruses that cause meningitis
are enterovirus as well as HSV.
So those are the most common ones that we do see
but there are a whole bunch of other viruses
that can also cause viral meningitis.
Now for the most part,
when we’re thinking about viral meningitis,
it’s important to note that while bacterial meningitis
can have a significant morbidity associated with that mortality,
especially those cause by enterovirus
and variety of other viruses
is actually relatively benign.
HSV is the one portion of viral meningitis
that requires more aggressive treatment
with an anti-viral medication.
And then fungal meningitis is the last big category here.
The most common fungal meningitis that occurs
is cryptococcal meningitis
and here you could see it on a special stain.
Viral meningitis is more common in the summer months.
And it’s more common in the summer months
due to increased prevalence of the enterovirus
during that time period.
So June, July, August
is gonna be the time period that it's most common.
Patients who have meningitis,
the classic symptoms that you think about are fever,
headache and altered mental status.
Now it’s important to note that these symptoms
are not all present in all people with meningitis.
So you wanna make sure you’re maintaining
a high level of suspicion for this condition.
Now some people do so say that fever,
headache, or altered mental status,
one of those needs to be present
in order to make the diagnosis of meningitis
and that’s likely true,
but just make sure that you’re thinking about this
and considering it for patients you present.
Photophobia is another classic symptom.
What that means is that the light will bother the patient’s eyes,
Classically, we think of shaking chills.
So a patient comes in and they say they were shaking,
their whole body were shaking all over,
they were having chills is a classic thing,
especially with especially with strep pneumo
that can be a classic thing that’s also associated with pneumonia.
And then neck stiffness,
we call that one of the big signs of meningismus.
So when you’re trying to talk with the patient
about what kind of symptoms they are experiencing,
asking them if their neck has been bothering them
or causing them pain is an important piece of the history.
And like I mentioned,
you wanna make sure you maintain
a high suspicion for this diagnosis,
especially in a patient who is immunocompromised.
Are they immunocompromised due to an underlying medical condition
or they’re immunocompromised due to medication
that can make them immunocompromised,
especially in transplant patients
or other people who have medications
that make them immunocompromised.
Older patients can always be tricky
and may not necessarily present with those classic symptoms.
And then patients who you're concerned with fungal meningitis
can be very tricky as well.
So these patients may all present with subtle symptoms.
Fungal meningitis can actually develop
over a much longer time period
and patients can have much vaguer symptoms.
So making sure that you’re thinking about that
and keeping it on your differential diagnosis is key.
The other important thing to keep in mind
and a good clinical pearl here
is that there's a higher incidence of seizures
in patients who have HSV related encephalitis.
So for patients who present with seizures,
and fever, and headache,
definitely, you wanna be thinking about HSV.
You also wanna make sure you’re thinking about
other risk factors for these conditions.
So what are the other key risk factors?
So again, the young and the old.
So little babies, older adults.
Patients who have had a splenectomy.
This is something that sometimes I actually forget to ask about.
So making it you know,
a common thing that you ask about in patients
who have had abdominal surgery.
Now some patients believe it or not,
might not actually know if they've had their spleen taken out.
So for those patients,
you wanna look at their belly and see if they have a scar.
The other thing to remember about the splenectomy is that,
in patients who have sickle cell,
they might have a splenectomy
where their spleen isn’t functioning effectively
due to the fact that that organ
doesn’t work effectively in patients with sickle cell
after a period of time
so keeping that in mind as well.
The immunosuppressed patients.
Patients who are on immunosuppressive medication
or have underlying medical problems
that make them immunosuppressed.
Any kind of recent neurosurgical procedure or a VP shunt.
A ventriculoperitoneal shunt,
so a shunt that goes from the brain into the peritoneal cavity.
Those are generally used if a patient
has an excess CSF or too much cerebrospinal fluid.
Now definitely in those patients,
as you can imagine,
if they've had their CSF or brain manipulated in anyway
or if they have a foreign body in their brain system.
That make sense if that would pre-disposed you to meningitis.
Intravenous drug use,
another thing that can predispose people to infections.
Definitely, if patients are using dirty needles
to inject the drugs into their veins,
that can predispose someone to getting a brain abscess
or an infection around their brain
that came from their blood stream.
And then closed quarters.
This is one of those things that can predispose to Neisseria,
'cause Neisseria can spread very rapidly and very quickly.
So anyone from a dorm or military barracks is key.