(almost) everything meninges

the meninges are the covering for the brain, so think of them padding the brain=

P-pia mater
A-arachnoid
D-dura mater

the pia mater is very popular, and others like sticking to it. the dura attaches to it via denticulate ligaments and the arachnoid attaches to the pia via trabeculations.

(however i can't forsee anyone ever being asked this during an exam or clinically, but still betcha didn't know that fact! everyone just thinks the three layers are atop of each other)

the pia forms the filum terminale at the end of the cord, and this joins the dura at S2.

infection of the meninges = meningitis.

Most Common Causative Agents:

newborn: group B strep
children: strep pneumoniae
adults: n. meningitidis
elderly: strep pneumoniae
HIV patients: cryptococcus neoformans (remember that post on capsulated organisms? it's a form of yeast with a capsule; stain with india ink)

(children and old people afflicted by same organism)

so clinical picture for meningitis: fever, headache, photophobia, neck stiffness.
physical examination: positive Kernig's and Brudzinki's signs.
Dx: LP to analyse CSF.

1. CSF in bacterial meningitis: high protein, high pressure, high WBC, low glucose (bacteria use up glucose)
2. CSF in viral meningitis: high protein, high lymphocyte, normal glucose (viruses have no use for glucose) 
3. TB meningitis: CSF same as viral meningitis EXCEPT glucose level would be very low.

complications of meningitis:

• encephalitis: sharp triphasic complexes on EEG
  *herpes encephalitis causes olfactory hallucinations and has mononuclear pleocytosis, along with RBCs in CSF
• adrenal haemorrhage (Waterhouse-Friderichsen syndrome): shell like calcifications on XR.

treatment:

1. DOC: 3rd generation cephalosporins + vancomycin
2. for cryptococcus neoformans: amphotericin B + flucytosine
3. prophylaxis for close contacts: rifampicin

and one last pearl before i end this post:

if patient has meningitis along with extremely high amylase levels, with no clear abdominal source (liver disease etc), think of acute viral parotitis.