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Meningitis is a relatively uncommon diagnosis, but one that warrants our full attention. MENING - refers to the meninges which are three protective membranes that cover the central nervous system (the brain and spinal cord). ITIS - refers to inflammation. So collectively, meningitis is simply an inflammation of the inner two layers of meninges. (the arachnoid and pia mater). The brain itself is generally not inflamed, if so, that would be a separate condition called encephalitis. On rare occasions the two conditions can run in parallel. It is important to call out that the subarachnoid space is positioned between these two layers and is responsible for housing the cerebrospinal fluid (CSF).

The CSF is normally a sterile fluid that should be clear and colorless. This fluid serves several roles which includes acting as a barrier/cushion. Additionally, it helps baths the CNS with important nutrients. The constituents of CSF include: rare white blood cells, several proteins and glucose. The CSF is an ultrafiltrate of our plasma, so the normal glucose range in CSF is about 2/3rd that of plasma. The brain is a highly metabolic organ, and it uses glucose at a pretty decent rate to carry out its most basic daily functions. Normal circulating volume of CSF is about 150ml, and it is continually being replenished and exchanged. Nearly 500ml/day are produced under normal circumstances.

Pathogens (viral, fungal, or bacteria) can enter this normally sterile space in a few ways. Sometimes you may have a congenital structure abnormality, like spina bifida or direct spread through your sinuses. Other times a traumatic injury could negatively disrupt the blood brain barrier. Additionally, septicemia (a systemic blood infection) could also overwhelm and cross the normally tight and selective barrier.

Viral - this condition is more common than bacterial meningitis. It is rarely life threatening. Viral meningitis can be caused by different viruses, and is spread between people by coughing or sneezing, or through poor hygiene. Full recovery is normal, sometimes without treatment, but headaches, fatigue, and depression may persist.

Bacterial - although rare, if this condition is not treated, it can be fatal. Many times, physicians will treat suspected cases with empiric antibiotics even before laboratory testing is completed. This is done because the untreated mortality rate approaches 100%. Vaccines are also commercially available for certain types of bacterial meningitis. This can be a great prevention strategy.

The following signs can be associated with meningitis; however, their absence doesn't rule out the disease, but their presence can be highly suggestive that meningitis exist. Keep in mind other diseases like spinal tumors, trauma, subdural hematomas, and MS may also elicit positive results. This may have limited pre-hospital utility and remember the gold standard is a lumbar puncture where CSF is testing in a hospital or reference laboratory.

Signs and Symptoms - a non-exhaustive list in no particular order

  • Fever

  • Altered mental status

  • Nuchal rigidity

  • Skin rashes/petechiae

  • Photophobia

  • Seizures

  • Headache (profound)

  • Irritability

Despite significant progress over the last few decades, meningitis remains a much-feared disease worldwide with a high case fatality rate and a propensity to cause epidemics that present a major challenge for health systems, economies and society. Meningitis caused an estimated 250 000 deaths in 2019, leaving one in five affected individuals with long-term devastating sequelae. As stated before, meningitis is a largely preventable disease through vaccination, but progress in the fight against the disease is behind other diseases preventable by vaccination.

May 27, 2024

Author: Joshua Ishmael, MBA, MLS(ASCP)CM, NRP

Pass with PASS, LLC

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