Infectious Brain Pathology - Clinical 

Fever + Petechiae
- Can't miss: neisseria + RMSF. Neisseria will progress to purpura fulminans
- Could also be other things: itp, ttp, etc

Blanching rash - common in west nile encephalitis

Meningococcemia
- Conjunctivial hemorrhage - thrombosis and gangene of extremities - purpura fulminans
- Sepsis +/- meningitis
- imparied consciousness and petechae may appear only later in the course
- non blanching purpuric rash
- Don't always see petechiae
- severe muscle pain of lower extremities is an early clinical sign.

DDx purpura fulminans
- meningiococcemia
- s.pneumo in people without spleen
- capnocyophaga canimorsus afer dog bite in asplenic patient
- vibrio vulnificans after raw oysters in cirrhotic patients

Severe bacterial meningitis - occurrence of symptoms 
HA, fever > 90%
menigismus > 85%
kernigs/bruzinsky > 50%
vom/sz > 30%
focal neruo deficit 10-20
papiledema <1%

If you suspect bacterial meningitis you have to tap - exam is not sensitive except in severe disease - meningismus/kernigs/brudzinski's - often absent in less severe cases

Aseptic meningitis ( = neg culture)
- usually due to viruses which is pretty benign
- other infectious etiologies - syphillis, TB, fungal (crypto, cocci, histo), ricketssia, leptosirosis, lyme dz
- non infectious - drug induced (ie drug allergy to IVIg, NSAIDs, bactrim), malignancy, lupus (ie lupus cerebritis - subacute presentation), paraneoplastic (antibody mediated autoimmune)

Viral menginitis
- Enteroviruses common, esp in summer and fall
- West nile common
- Mumps in non vaccinated kids
- HSV2 - causes recurrent aseptic meningitis -  Bad for neoates but in immunocompetent adults usually causes a benign viral meningitis - (vs HSV1 causes more encephalitis and is worse )
- VZV, EBV
- CMV if immunocompromised
- Arboviruses - west nile, La Crosse, st louis
- Acute HIV
- Lymphocytic chroiomeningits virus - mice and hamster pets
- Resp viruses: measles, influenza, adenovirus, paraflu
- Don't test for everything - test for can't miss/must treat (HSV2, HIV) and for common things (enteroviruses, west nile)

Management: 
- Steroids, blood cx, start abx, LP.
- Blood cx before abx but don't delay your abx if waiting for scan or tap.

CI to LP
- absolute: infected skin, trauma
- relative: coagulopathy/thrombocytopenia, increased intracranial pressure/mass effect
- When you should def get CT before LP: age > 60, immunocomp, papilleedema, altered consciousnss, focal deficit, new onset sz, known cancer, known cns lesions, suspect brain abscess (ivdu, endocarditis, local parameningial infeciton- dental/sinusitis/otitis
- If the CT shows supratentorial and infratentorial pressure differential - loss of cisterns, posterior fossa mass

LP complications
- HA ( low pressure HA - improves with lying down) - if it doesn't resolve, may have CSF leak - blood patch
- back pain
- infection
- bleeding - coag abnl, spinal subdurla/epidural hematomas
- hernation

CSF tests: 
- cell count, glucose total protein, gram stain
- vdrl, lyme, crypto ag
- pcr for entero, hsv, vzv, ebv, cmv
- csf ab for west nile
- keep 1 tube of csf in case you need add'l testing (tb, aids, jcv, ebv, cmv, toxo)

Bact meningitis by age
- 0-4 wks : GBS, e.coli, listeira, kleb, enterococcus, salmonella
- 5-12 wks: GBS, ecoli, list, hib, spnemoneisseira
- 3 mos- 18 yrs: h flu (rare these days s/p HiB vaccine), neisseria, s.pneumo
- 18 - 50 yrs: s penumo, neisseira
- >50 yrs: s.pneumo, neisseria, listeria, gram negs

Empiric tx bacteria menigntis - acute onset of fever and HA
- HIGH DOSE Vanc and ceftriaxone
- + Amp for babies and old people - Gram stain often neg in listeria
- Steroids EARLY - s.pneumo, H flu, TB most benefit with steroids

Subacute/chronic meningitis
- immunocompetent: neurosyphilis, crypto. TB, coccidio, histo

Encephalitis
- immunocomptent: arboviruses (west nile, EEE), vzv, lymphochoriomeningiis

Recurrent neisseria meningitis: 
- terminal complement deficiency
- more benign course of meningoccemia meningitis

Recurrent meningits with Upper resp colonizers s.pneumo, think of csf leak