Key Feature 1: In the patient with a non-specific febrile illness, look for meningitis, especially in patients at higher risk (ex: immunocompromised individuals, alcoholism, recent neurosurgery, head injury, recent abdominal surgery, neonates, aboriginal groups, students living in residence).
Skill: Clinical Reasoning, Selectivity
Phase: Hypothesis generation
Key Feature 2: When meningitis is suspected ensure a timely lumbar puncture.
Key Feature 3: In the differentiation between viral and bacterial meningitis, adjust the interpretation of the data in light of recent antibiotic use.
Skill: Clinical Reasoning
Key Feature 4: For suspected bacterial meningitis, initiate urgent empiric IV antibiotic therapy (i.e., even before investigations are complete).
Skill: Selectivity, Clinical Reasoning
Key Feature 5: Contact public health to ensure appropriate prophylaxis for family, friends and other contacts of each person with meningitis.
Skill: Clinical Reasoning, Professionalism
In a patient who has a fever without a localizing source, it is important to consider the many possible sources of infection before considering other systemic reasons for which a fever may be occurring. Possible infections include:
Depending on how unwell the patient is, and what their risk factors are for acquiring or fighting off various infections, the selection and speed of investigations will vary. In this post, I will focus on the possibility of meningitis in a patient without a known source of infection.
I am currently working in an intermediate nursery (the stepping stone between a nursery for healthy babies and a neonatal intensive care unit). Neonates are one of the populations at increased risk for acquiring meningitis. Other risk factors for acquiring meningitis, listed in Key Feature 1 of the CFPC Priority Topic: Meningitis, include other host features, such as being immunocompromised (for various reasons, such as chronic disease, taking corticosteroids, or by not having been vaccinated against the usual bacterial culprits), having an alcohol use disorder or injecting drugs, and/or having increased exposure to others who may have and who may spread the bacteria that can cause meningitis, such as may occur with people living in aboriginal groups or in student dormitories. One's risk for acquiring meningitis can also increase depending on risk from particular events that have happened, such as trauma, be it unintentional (ex: head injury) or intentional (ex: recent neurosurgery or recent abdominal surgery). If a patient is at increased risk for host or environmental reasons, and they have a fever without a localizing source, the clinician's degree of threshold for investigating for possible meningitis is lowered. And, out of all the factors that increase one's risk for meningitis, being less than 1 month of age is the greatest. Thus, any neonate less than one month old presenting with sepsis (which has many possible signs and symptoms, but that most frequently presents with hyperthermia, respiratory distress, and tachycardia, see table below) warrants an infectious workup that includes looking for meningitis. According to UpToDate, "A child with two or more of the criteria for the systemic inflammatory response syndrome (see below) who also has suspected or proven infection has sepsis." If localizing neurologic signs are present, they may include irritability, lethargy, poor tone, tremors or twitching, and seizures. Signs that classically associated with neonatal meningitis, that of a bulging fontanelle and nuchal rigidity, are according to UpToDate, apparently the exception rather than the norm. Even in older children, the usual presentation of meningitis is not usual or following a classic pattern, although old medical authorities would have described classic findings of meningitis as fever, headache, and neck stiffness.
The UpToDate article, "Bacterial meningitis in the neonate: Clinical features and diagnosis," states, "Because the clinical presentation of bacterial meningitis in the neonate is nonspecific, neonates with suspected bacterial meningitis should undergo a full laboratory evaluation for sepsis. This includes a complete blood count with differential, blood culture, urine culture (if >6 days of age), and lumbar puncture (LP) (for cerebrospinal fluid [CSF] cell count, protein, glucose, Gram stain, and culture). Examination of the CSF is necessary to establish the diagnosis of bacterial meningitis."
I am currently working in a level 2 nursery, providing care for infants who are not entirely well but who also aren't unstable to the point of needing to be in the neonatal intensive care unit. This past week, I encountered a newborn with suspected sepsis. The infant was started on antibiotics as soon as the possibility of sepsis was on the diagnostic table. By the time the blood cultures came back (48 hours after they were drawn) and showed evidence of bacteremia, the neonate had been on IV antibiotics for almost just as much time. There was question of possible infectious meningitis, and the Pediatric Infectious Disease team was consulted. They requested that a lumbar puncture still be obtained, because even though there is a good chance the CSF would be sterile secondary to already receiving 2 days of IV antibiotics, there was a chance that the other components of the CSF would show signs of bacterial meningitis. The ID team argued that these other findings would make a stronger case for a diagnosis of suspected bacterial meningitis and would suggest prolonging antibiotic therapy (or, if the CSF is unremarkable for signs of bacterial infection, this would mean that antibiotics could be discontinued sooner rather than later). That evening, the attending physician performed a lumbar puncture on the infant. From this case I learned that, ideally, anytime blood cultures are being drawn for suspected sepsis in a neonate, a lumbar puncture is also done at around the same time and before antibiotics are started, so that a definite diagnosis of meningitis can be made by actually detecting the bugs, if present, before they are killed, presuming the neonate is not already on death's doorstep.
When I return to work tomorrow and reassess this patient and the findings of their LP, what findings would suggest a bacterial or viral meningitis? According to UpToDate Date, neonatal CSF interpretation can be somewhat ambiguous, as there is quite a bit of natural variation in the components of the CSF among healthy neonates. There are some features, however, that make a stronger case for bacterial or viral infection.
Findings that make bacterial meningitis more likely:
UpToDate also goes on to explain that, "Analysis of the CSF is not always predictive of viral or bacterial infection, since there is considerable overlap in the respective CSF findings."
Furthermore, after antibiotics are administered and an LP is done after some time (so like not immediately afterward), you do get a shift in the glucose and protein that makes these markers even less useful. Apparently the WBC count is less affected by the antibiotic, so there may still be some utility in looking at the CSF for that indicator.
So basically, it really is the presence of an organism on CSF Gram stain and culture, or a positive result from virology studies that can, and that only can, really clinch the diagnosis. Learning point reiterated: If the patient with suspected meningitis is not about to die, get an LP done STAT right before starting antibiotics, or at least as soon as possible without compromising the administration of antibiotics. UpToDate suggests a target of starting antibiotics within 60 minutes of the infant presenting to your care. If the LP is delayed, then going ahead and giving antibiotics before waiting for the LP to be done is necessary and could mean the difference between life and death. Once all the initial kerfuffle is addressed, it is important to report the suspected or confirmed case of meningitis to the regional public health authority as it is one of the mandatory notifiable diseases. A complete list of the notifiable diseases for the province of British Columbia can be accessed here.