CNS Infections

Question 1

Blood Brain Barrier

Answer 1

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.

Question 2

Pathogens of Community Acquire Bacterial Meningitis

Answer 2

streptococcus pneumoniae, neisseria meningitidis, listeria monocytogenes, H. influenza

Question 3

What does s. pneumoniae infect?

Answer 3

ears, sinus, lungs and spreads to blood stream

Question 4

What does n. meningitidis infect?

Answer 4

isolated sporadic infection or epidemic, attacks nasopharynx -> sore throat

Question 5

What does listeria monocytogenes infect?

Answer 5

attacks the weak, youmg, or prego (GI mediated)- food

Question 6

Primary sites of infection leading to bacterial meningitis

Answer 6

most commonly blood borne, primary infections of the ears, sinuses, throat, lungs, heart and GI tract via basilar skull fracture

Question 7

CSF findings that indicate bacterial meningitis

Answer 7

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

Question 8

Indications for LP

Answer 8

no focal neurological deficits are present and no papillodema, no AIDS patients on immunosuppressants- higher frequency of cortical space occupying lesions

Question 9

What do you do if you cant get and LP?

Answer 9

send for CT, get a blood culture and treat

Question 10

T/F: Gram stain is 75% gram pos for bacterial meningitis

Answer 10

True

Question 11

Tx for bacterial meningitis

Answer 11

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

Question 12

Etiologies for Viral Meningitis

Answer 12

enteroviruses, echinoviruses and coxsackie viruses

Question 13

Clinical manifestations of viral meningitis

Answer 13

headache, stiff neck, photophobia, conjunctivitis, rash

Question 14

Dx of viral meningitis

Answer 14

CSF: increased lymphocytes, normal glucose, mild protein increase. PCR can make dx of HSV and enterovirus

Question 15

Tx of Viral meningitis

Answer 15

supportive care: adequate hydration, antipyretics, antiemetics, analgesia (for headaches). IF HSV use antiviral therapy AND supportive (IV acyclovir)

Question 16

Cryptococcal Meningitis

Answer 16

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.

Question 17

Symptoms of Cryptococcal Meningitis

Answer 17

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)

Question 18

Dx of Cryptococcal Meningitis

Answer 18

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

Question 19

Aseptic meningitis (signs and symptoms)

Answer 19

headache, neck stiffness, photophobia, nausea during primary HIV infection

Question 20

Lab findings for asceptic meningitis

Answer 20

moderate to no immunosupression; moderate rise in CSF count

Question 21

Tx for asceptic meningitis

Answer 21

no specific tx, spontaneously resolves

Question 22

Encephalitis

Answer 22

3 major categories: mosquito borne (arbovirus), animal to human (rabies), human to human (herpes)

Question 23

Symptoms of encephalitis

Answer 23

hallucinations, seizures, ataxia (w/rabies ascending paralysis, rapid short respirations, possibly RBCs)

Question 24

Dx of encephalitis

Answer 24

CSF: WBC below 500, mild increase in protein, possibly RBCs. May need brain biopsy to dx

Question 25

Tx of encephalitis

Answer 25

acyclovir

Question 26

Brain Abscess

Answer 26

symptoms initially nonspecific and delay in dx is common. Severe head ache at point of abscess. Alterations in mental status and neck stiffness. Vomiting and INCREASED ICP. Can be caused via direct ear infection, dental infection or frontal sinus.

Question 27

Dx of brain abscess

Answer 27

MRI not CSF

Question 28

Tx of Brain abscess

Answer 28

PCN or metronidazole