CNS Infections Flashcards
Blood Brain Barrier
tight junctions linking endothelial cells of vessels in the brain. This protects the CNS from invading pathogens or toxic substances. (the limiter permeability acts as a barrier). It also prevents entry of immunoglobulins, compliment and abx. Thus if a pathogen gets here there is rapid progression.
Pathogens of Community Acquire Bacterial Meningitis
streptococcus pneumoniae, neisseria meningitidis, listeria monocytogenes, H. influenza
What does s. pneumoniae infect?
ears, sinus, lungs and spreads to blood stream
What does n. meningitidis infect?
isolated sporadic infection or epidemic, attacks nasopharynx -> sore throat
What does listeria monocytogenes infect?
attacks the weak, youmg, or prego (GI mediated)- food
Primary sites of infection leading to bacterial meningitis
most commonly blood borne, primary infections of the ears, sinuses, throat, lungs, heart and GI tract via basilar skull fracture
CSF findings that indicate bacterial meningitis
increased WBC (more than 90% PMNs)- PMNs increase at site as organism proliferates; lyse and lead to tissue necrosis- Hypoglycorrachia (low glucose)-due to inflammation of arachnoid and pia matter, Rise in protein- due to leakage of serum from damaged vessicles, Increased ICP
Indications for LP
no focal neurological deficits are present and no papillodema, no AIDS patients on immunosuppressants- higher frequency of cortical space occupying lesions
What do you do if you cant get and LP?
send for CT, get a blood culture and treat
T/F: Gram stain is 75% gram pos for bacterial meningitis
True
Tx for bacterial meningitis
tx with in 30 min, maximal dose abx b/c of limited passage through BBB. Give dexamethasone before abx to prevent neurological damage.————————————————————————-If 3mo-60yr give ceftriaxone or cefotaxime (3rd gen ceph), if severely ill give vancomycin, in >60yo or immunocomprimised give ceftriaxone/ceftotaxime PLUS ampicillin PLUS vancomycin. If nosocomial give vancomycin PLUS ceftazidime/cefepime
Etiologies for Viral Meningitis
enteroviruses, echinoviruses and coxsackie viruses
Clinical manifestations of viral meningitis
headache, stiff neck, photophobia, conjunctivitis, rash
Dx of viral meningitis
CSF: increased lymphocytes, normal glucose, mild protein increase. PCR can make dx of HSV and enterovirus
Tx of Viral meningitis
supportive care: adequate hydration, antipyretics, antiemetics, analgesia (for headaches). IF HSV use antiviral therapy AND supportive (IV acyclovir)
Cryptococcal Meningitis
organism is inhaled, high concentrations of yeast like fungus in pidgeon droppings. Thick capsule that is immunosuppressive. Produces melatonin and manitol which increase virulence and increase cerebral edema.
Symptoms of Cryptococcal Meningitis
Severe intermittent headache is most common symptom. Also personality changes, stupor/coma. More common in immunosuppressed patients (AIDS). Can have occular motor palsies and hearing loss (decreased visual acuity and diploplia)
Dx of Cryptococcal Meningitis
LP: WBC 20-200 (predominance of mononuclear cells), mild protein elevation, moderate decrease in glucose. Mix 1:1 with india ink to see encapsulated particles. CT and MRI show discrete cryptococcomas
Aseptic meningitis (signs and symptoms)
headache, neck stiffness, photophobia, nausea during primary HIV infection
Lab findings for asceptic meningitis
moderate to no immunosupression; moderate rise in CSF count
Tx for asceptic meningitis
no specific tx, spontaneously resolves
Encephalitis
3 major categories: mosquito borne (arbovirus), animal to human (rabies), human to human (herpes)
Symptoms of encephalitis
hallucinations, seizures, ataxia (w/rabies ascending paralysis, rapid short respirations, possibly RBCs)
Dx of encephalitis
CSF: WBC below 500, mild increase in protein, possibly RBCs. May need brain biopsy to dx
