00:00
In this lecture, we're going to discuss Pediatric Meningitis. Vaccines have been a valuable tool
in reducing rates of meningitis in children. Specifically, the <i>H. flu</i> type B vaccine has virtually
eliminated <i>H. flu</i> B meningitis from the United States. The anti-streptococcal vaccines have been
very beneficial at reducing substantially but not eliminating rates of streptococcal meningitis.
00:31
The <i>Neisseria meningitidis</i> vaccine which is primarily given to children before they go to college
has been very effective at reducing college outbreaks of <i>Neisseria meningitidis</i> meningitis which is
highly infectious and highly dangerous. Additionally, both the varicella and the influenza vaccines
reduce rates of viral encephalitis and viral meningitis. So, how does meningitis happen? Well,
we have to recognize that bacteria are constantly colonizing our nasopharynx. During some
freakish event, the bacteria invades with the mucosa and get in to the bloodstream and then they
generally get up to the brain and they may penetrate the blood-brain barrier. This is how this
infection happens. It will present in infants differently than it will in older children. Infants or
newborns will present with fever, irritability and lethargy, excessive crying and either hypo- or
hyperthermia so a low temperature or a high temperature. What's key is the irritability. We
usually see that as predominant and we worry about this in pretty much all young infants with
fever as our rule out sepsis protocol. In terms of older children, they will present with fever
but these children will more often have vomiting, headache, photophobia, confusion and what's
key is a stiff neck. If you have a patient like that with a stiff neck and unwillingness to touch
their chin to their chest, you definitely should be worried about meningitis. Nuchal rigidity is the
physical exam hallmark of this diagnosis and they usually have difficulty pushing their head
forward on to their chest. You may further make the diagnosis by looking for the Kernig and
Brudzinski signs. You recall what those are. Those are basically where the patient has difficulty
raising the neck or the patient has pain while the doctor raises the hip. Patients may have
petechiae and purpura that would be consistent with <i>Neisseria meningitidis</i>. Here is the Kernig
and Brudzinski sign that I described. You can see Kernig sign where the hip is raised up and the
Brudzinski sign where the head goes up and then the knees flex reflexibly. If you have a hard
time remembering which is which, remember Kernig's is knee, k and k. In meningitis, we'll get
some labs to try and make this diagnosis. Let's start with some non-specific labs. The CBC may
be elevated in meningitis but it might not. So this is not a definitive test. We will often get a
blood culture in meningitis and occasionally it will reveal what the causative organism is but the
best culture is of the spinal fluid. In infants, we're also checking urine. We're checking it
because we don't know whether this is a urinary tract infection, a blood infection, or meningitis.
03:42
What's key to understand is an unusual phenomenon in adults but is common in children which is
that children with a urinary tract infection will get a low level sterile pleocytosis in the CSF.
03:56
What that means is a child with a urinary tract infection and lots of white cells in the urine may
have a low number of white blood cells in their spinal fluid but not have meningitis. This
highlights the need for getting the tap before giving antibiotics because if you get the tap
after giving antibiotics, you sterilize the CSF and it will be impossible to distinguish a patient
who has both the UTI and meningitis from a child who has a UTI and a sterile pleocytosis. So the
test of choice for any child where you're concerned about meningitis is obviously a lumbar puncture
and we're going to get that fluid and we're going to send it off to the lab. What are we going to
send it for? Well, first we're going to send it for a gram stain. The CSF gram stain has a high false
negative rate but a low false positive rate. What that means is if you see bacteria, you should
be worried but if you don't you're about where you started. Let's also send that CSF for protein.
04:59
In bacterial disease, this is usually very high. We should also send that CSF for glucose. Usually,
the bacterial disease, the glucose is low, less than 2/3 of whatever the serum value is. Likewise,
we're going to send that CSF for a cell count and specifically ask about the number of white
blood cells. Patients with meningitis will have a higher than 21 white count if they're under 4
weeks of age, 4-8 weeks it should be less than 11. In other words kids with meningitis will have
more than 11 cells. After about 8 weeks we expect a normal patient to have less than 8 cells.
05:40
So more than 8, that's concerning.