Section 6: CNS Infections Flashcards
Indicatiosn for CT scan before LP
- A history of central nervous system disease
- Focal neurologic deficit
- Presence of papilledema
- Seizures
- Altered consciousness
- Significant delay in the ability to perform an LP
Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kindle Locations 7219-7220). . Kindle Edition.
A 45-year-old man comes to the emergency department with fever, headache, photophobia, and a stiff neck. What is the next best step in the management of this patient?
a. Lumbar puncture
b. Head CT scan
c. Ceftriaxone and vancomycin
d. Penicillin
e. Movement of patient to ICU
Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kindle Locations 7224-7234). . Kindle Edition.
A. When you suspect bacterial meningitis, administer antibiotics quickly. Further, do blood cultures stat simultaneously with a lumbar puncture (LP), or immediately prior. Penicillin can never be used as empiric therapy for meningitis; it is not
Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kindle Locations 7224-7234). . Kindle Edition.
Most accurate diagnosis for bacterial meningitis
Culture of CSF
Diagnosis:
Gram-positive diplococci
Gram-negative diplococci
Gram-negative pleomorphic, coccobacillary organisms
Gram-positive bacilli
Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kindle Locations 7241-7248). . Kindle Edition.
Pneumococcus
Neisseria
Haemophilus
Listeria
Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kindle Locations 7241-7248). . Kindle Edition.
True or False:
The Gram stain has poor sensitivity but good specificity for bacterial meningitis.
Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kindle Locations 7241-7248). . Kindle Edition.
True
Normal CSF findings
- Protein = 10-45 mg/dL
- Glucose = 40-80mg/dL
- Pressure = 60-180mmH2O
- Leukocyte, total = <5/mm3
- Lymphocytes 60-75%
- Monocytes 25-50%
- Neutrophils 1-3%
- Cell count 0-5 lymps/HPF
CSF findings in pyogenic meningitis
- Cells/ml → 200-5,000
- Cytology → PMN
- Glucose → Low (below 60% of serum level)
- Protein → High
- Gram stain → Positive
- CIE or LA → Positive
- Pressure → High
CSF findings in meningitis that has been partially treated
- Cells/ml → 200-5,000
- Cytology → Mostly PMN
- Glucose → Low
- Protein → High
- Gram stain → Variable
- CIE or LA → Positive
- Pressure → High
CSF findings in granulomatous disease e.g TB
- Cells/ml → 200-500
- Cytology → Lymphocytes
- Glucose → Low
- Protein → High
- Gram stain → Negative
- CIE or LA → Negative
- Pressure → High
CSF findings in aseptic meningitis
- Cells/ml → 100-700
- Cytology → PML, Lymphocytes
- Glucose → Normal
- Protein → Slightly high
- Gram stain → Negative
- CIE or LA → Negative
- Pressure → Normal
CSF findings in Neighborhood reaction
- Cells/ml → 100-500
- Cytology → Variable
- Glucose → Normal
- Protein → Variable
- Gram stain → Negative
- CIE or LA → Negative
- Pressure → Variable
Best initial test for diagnosis of meningitis
Cell count
- Although not as specific as a culture, it is available much sooner
- Cell count with a differential is much more specific than an elevated CSF protein level
- If thousands of neutrophils are present in the CSF, start IV ceftriaxone, vancomycin, and steroids. Steroids have been associated with a decrease in mortality in bacterial meningitis
- CSF cell count is the most important criterion to determine the need to treat a patient. Thousands of polys (neutrophils) indicate bacterial meningitis until proven otherwise.
Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kindle Locations 7253-7260). . Kindle Edition.
An elderly man comes to the emergency department with fever, headache, a stiff neck, and photophobia. He is HIV positive with CSF shows 2,500 white cells that are all neutrophils; Gram stain is normal. What is the best initial therapy?
a. Ceftriaxone and metronidazole
b. Cefoxitin and mefloquine
c. Ceftriaxone, ampicillin, and vancomycin
d. Fluconazole
e. Amphotericin
Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kindle Locations 7294-7301). . Kindle Edition.
C. Listeria monocytogenes is a cause of meningitis that is not adequately treated by any form of cephalosporin. Ampicillin is added to the usual regimen of ceftriaxone and vancomycin to cover Listeria. This cannot be fungal meningitis, because the CSF is characterized exclusively by a high number of neutrophils; neutrophils are not consistent with fungal meningitis.
Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kindle Locations 7302-7316). . Kindle Edition.
A 17-year-old male is brought to the emergency department with fever, headache, stiff neck, and photophobia. He has a petechial rash. CSF shows 2,499 neutrophils. Ceftriaxone and vancomycin are started. What should be done next?
a. Test for HIV
b. Wait for results of culture
c. Add ampicillin
d. Enforce respiratory isolation
e. Enforce respiratory isolation and prescribe rifampin for close contacts
Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kindle Locations 7302-7316). . Kindle Edition.
E. When an adolescent presents with a petechial rash and increased neutrophils on CSF, it is suggestive of Neisseria meningitidis. These patients should be placed on respiratory isolation, and close contacts should receive prophylaxis.
Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kindle Locations 7302-7316). . Kindle Edition.
List those susceptible to listeria meningitis
Elderly
Neonates
HIV-positive patients
Asplenic patients
Those on steroids
Immunocompromised with leukemia or lymphoma
Rx for listeria meningitis
Ampicillin
Susceptible for Neisseria meningitides
Adolescents
Military personnel
Asplenic patients
Terminal complement deficiency
Apart from antibiotics, what other measures should be taken for those with meningitis due to Neisseria meningitides?
- Patient: Begin respiratory isolation
- Close contacts: Start prophylaxis with rifampin, ciprofloxacin, or ceftriaxone for close contacts, such as household members and those who share utensils, cups, or kisses
- Routine contacts: Routine school and work contacts do not need to receive prophylaxis.
The nurse or medical student taking care of a patient with Neisseria does not need prophylaxis. Those with kissing and other saliva-type contact do need prophylaxis.
Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kindle Locations 7323-7327). . Kindle Edition.
- Fever + confusion
- Main cause of (1) above in the US
- Best initial test for above diagnosis
- Most accurate test for above diagnosis
- Best initial Rx
- For resistance to initial Rx
- Encephalitis
- Herpes
- Head CT scan
- PCR of the CSF (Brain BIOPSY is not correct)
- Acyclovir
- Foscarnet
HIV-positive patient with CD4 count less than 100, and features of meningitis
- Diagnosis
- Best initial test
- Most accurate test
- Best initial Rx
- Additional Rx
- Cryptococcus
- India ink stain
- Cryptococcal antigen
- Amphotericin B
- Add oral fluconazole. If patients CD4 does not rise Rx for life. If it increases above 100 fluconazole can be stopped
Rx for TB meningitis
- Rifampicin
- Isoniazid (INH)
- Pyrizinamide
- Ethambutol
- Steroids
Use the mneumonic RIPE(S)
Rx is usually longer than in pulmonary TB
CF of brain abscess
- Fever
- Headache
- Focal neurological deficits
- Contrast enhancing lesion on CT scan of the head
- Diagnosis:
- Patient is immigrant from Mexico
- Seizure
- Head CT with multiple 1 cm cystic lesions; possible calcification of lesions
- Confirmatory diagnostic test
- Rx of above diagnosis
- Neurocysticercosis
- Serology
- Albendazole + Steroids
Empiric antibiotic choice for meningitis in the neonate
- 0-7 days: ampicillin plus gentamicin
- >7 days: (and gram negative suspected), add cefotaxime
Empiric antibiotic choice for meningitis in the adolescent
IV ceftriaxone plus vancomycin
Empiric antibiotic choice for meningitis in the adult
IV ceftriaxone plus vancomycin and steroids
Empiric antibiotic choice for meningitis in the immunocompromised (HIV, leukemia and lymphoma patients) and >50 years
Add ampicillin to empiric Rx for adult
