Weatherly's Woes - Meningitis

MENINGITIS (BACTERIAL)

Spinal Meningitis

Bacterial Meningitis is inflammation of the CSF and meninges caused by, duh, a bacterial infection. This is a medical emergency.

How do you spot it?

The classic triad is Fever + Neck Stiffness + Headache. The fever will be high (over 100). In real life, neck stiffness (aka nuchal rigidity) is pretty darn obvious. But on the test, they will mention a positive Kernig or Brudzinski test (neither of which are used in the real world btw). There are a few other possible symptoms. Confusion, vomiting and photophobia are going to occur maybe 50% of the time. A petechial rash is associated with meningitis caused by Neisseria meningitidis.

How do you diagnose it?

The only test for meningitis is a lumbar puncture. The CSF that emerges from their back is yellow and pus-like in severe cases. In milder cases the CSF may just look cloudy (CSF is supposed to look like water). When you send the CSF to the lab for analysis, the report will show ↑neutrophils and ↓glucose (the bacteria eat the glucose). There is also usually ↑protein, but I find this less helpful.

Which bugs cause meningitis?

Overall, Strep pneumoniae is the most common pathogen. But you have to break it down by age.

Newborns - Strep agalactiae (commonly called Group B Strep, or GBS) is the most common culprit. Neonates usually catch meningitis from the flora of their mother’s vaginal canal. GBS is a great example of medicine going right -- some doctors figured out that we can swab expectant mother’s shortly before their due date, and now we can give them antibiotics to clean out the GBS infection, preventing neonatal GBS meningitis! The next most common causes are E. coli and Listeria monocytogenes (Listeria can be avoided if mom doesn’t eat soft cheeses during pregnancy).
Kids - Strep pneumoniae is the most common cause. Haemophilus influenzae is common in UNVACCINATED kids.
Teens - Strep pneumoniae is the most common cause. But now you have to also consider Neisseria meningitidis. The meningococcal vaccine starts to wear off around the time people turn 18. Just as the vaccine starts to wear off, teens are going to college or the military -- bunking up together in dorms. This is a recipe for disaster. It enters the body through the nose and spreads via the blood to the CSF. Meningitis spreads through aerosolized droplets like wildfire through dorm rooms, army barracks and prisons.
Adults - Strep pneumoniae is the most common cause. But over the age of 50, Listeria becomes a problem.

How to treat it?

Give antibiotics ASAP. Ceftriaxone, vancomycin and steroids every time. Throw in ampicillin when you suspect Listeria. When should you suspect Listeria? AIDS, neonates and the elderly (over 50). Give Ampicillin and Gentamicin to kids.

N. meningitidis causes a petechial rash. Petechial rashes are non-blanching - they don’t disappear when you squish them (most rashes do blanch when you compress them, try it). Roll a piece of glass over the rash to get a good look!

MENINGITIS (VIRAL)

Aseptic Meningitis

Viral Meningitis is like Diet Meningitis©. It’s got the symptoms you know and love, just much milder.

Symptoms?

Many people who get it don’t even go to the doctor, they just write it off as a tension headache or flu-like illness. But the classic triad applies here too: fever, neck stiffness and headache. The fever is often low grade (around 100), and the neck stiffness is pretty mild.

Which viruses cause meningitis?

Coxsackievirus B is the most common cause of viral meningitis. It spreads fecal-orally (Coxsackie A causes hand-foot-mouth disease). Coxsackievirus is an enterovirus (it enters through our gut). Mumps can cause viral meningitis in the unvaccinated -- it also causes swelling in the testicles and cheeks. Herpes can cause aseptic meningitis as well. HSV-2 is more likely to affect the meninges than HSV-1 (which more likely hits the brain). In the grand scheme of things, it's very unlikely for someone with herpes to get meningitis, but it happens in immunocompromised people. Some of the vector-borne viruses can cause viral meningitis. This includes the mosquito-borne (Culex) West Nile Virus (which weirdly enough is more common in the US than in Egypt), and other unusual viruses like St. Louis encephalitis or Equine encephalitis.

Diagnosis?

The only way to diagnose meningitis is with a lumbar puncture. The CSF will have ↑lymphocytes and normal glucose.

Why is bacterial meningitis more dangerous?

Bacteria attract neutrophils. Neutrophils make pus. The skull is a closed space. Pus in the skull → raised ICP → herniation → death.