Meningitis (pediatrics): Clinical sciences

Meningitis refers to the inflammation of the meninges, which are protective membranes that surround the brain and spinal cord. Meningitis commonly occurs as a result of bacterial infection. In newborns, the most frequent causative pathogens include Group B streptococci, Escherichia coli, and Listeria monocytogenes; while in children and teens, more common causes include Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis. Finally, if there are no bacteria, consider aseptic forms of meningitis, such as viral meningitis!

Now, if your patient presents with a chief concern suggesting meningitis, perform an ABCDE assessment to determine whether the patient is unstable or stable. If unstable, stabilize their airway, breathing, and circulation. Next, obtain IV access, start IV fluids, and put the patient on continuous vital sign monitoring, including blood pressure, heart rate, and pulse oximetry. Finally, if needed, don’t forget to provide supplemental oxygen.

Now, let’s go back and take a look at stable patients. First, assess your patient’s age, since the diagnostic evaluation and management are age-dependent. The main cut-off is at age 60 days.

Let’s start with patients 60 days of age and younger. Start by obtaining a focused history and physical exam. History typically reveals non-specific symptoms, such as fussiness, inconsolability, sleepiness, weakness, or even apnea. Additionally, caretakers might report vomiting, poor feeding, and, in some cases, even seizures. The physical exam typically reveals temperature instability, poor tone, irritability when moved, and lethargy. In some cases, you might notice increased head circumference, as well as full or bulging anterior fontanelle.

At this point, you should suspect meningitis! Begin your diagnostic workup by ordering labs, including blood cultures, a CBC, and inflammatory markers, including CRP and procalcitonin. Additionally, perform lumbar puncture to obtain CSF for analysis, which includes a gram stain, culture, and cell count, as well as glucose and protein levels.

Once you obtain these labs, begin treatment with intravenous empiric antibiotics, including ampicillin to cover for Listeria, in combination with cefotaxime or gentamicin to cover for other potential bacterial causes. Remember, if there’s high suspicion for bacterial meningitis, and your patient is critically ill, don’t delay administering antibiotics for the sake of performing a lumbar puncture first!

Here’s a high-yield fact! Although ceftriaxone is the antibiotic of choice in other age groups, it should be avoided in neonates, since it displaces bilirubin from albumin binding sites, putting the patient at risk for kernicterus.

Next, assess the initial lab results. First, let’s focus on infants with aseptic meningitis. The CBC typically reveals a normal or low white blood cell count, with or without a low platelet count. In addition, in most cases, the CRP is elevated and the PCT is normal. Meanwhile, the CSF gram stain will be negative, and CSF fluid analysis will reveal a lymphocytic pleocytosis, with normal glucose and normal to high protein.

At this point, you should suspect aseptic meningitis, so your next step is to order a CSF viral PCR, and then assess the PCR and culture results. If PCR identifies a viral pathogen, and CSF and blood cultures remain negative, you can diagnose viral meningitis. At this point, you can discontinue antibiotics. Management primarily consists of supportive care, but be sure to begin IV acyclovir if CSF PCR is positive for HSV!

Here’s a high-yield fact! Because acyclovir can cause kidney damage, patients on this medication should receive IV fluids to ensure adequate renal perfusion.

Okay, now let’s go back to our labs and discuss bacterial meningitis. In this case, the CBC usually reveals a normal or low white blood cell count, with or without a low platelet count, and almost always elevated CRP and procalcitonin levels. Next, the CSF gram stain will usually be positive, with gram-positive cocci suggesting Group B Streptococcus, or Streptococcus agalactiae; gram-negative rods suggesting E. coli; or gram-positive bacilli suggesting Listeria monocytogenes. Additionally, CSF analysis reveals neutrophilic pleocytosis, low glucose, and high protein levels.

The presence of these findings should make you suspect bacterial meningitis, so your next step is to assess culture results! A positive CSF culture, with or without a positive blood culture, confirms the diagnosis of bacterial meningitis, so make sure to tailor the antibiotic regimen based on culture results.