TB Meningitis

 

Cool points:

- TB engulfed by macrophages, but ineffective killing

- interferon gamma can cure TB

- not that easy to get TB - 50% after living with someone with it for 6 months

- 90% infected people never get active TB

- kids (<5yrs), immunocompromised people more likely to start with active TB with primary infection

- major risk factor is birth in a high risk country, most in Canada is foreign-born

- also risks of healthcare workers, serious travel to high-risk countries, close contact to active cases, age, immunocompromised

- high-risk countries: Europe as source, now high in Asia and Africa (worse with HIV), also South America. Especially India, China, Philipines, Russia, Pakistan...

-TB meningitis diagnosis? Do a CXR to R/O active, infectious lung TB

 

Purified protein derivative (Mantoux)

- very crude test

- cross reaction with non-TB mycobacteria including BCG vaccine

- BCG vaccination as infant, PPD+ for 5 yrs. Older you are, longer it takes.

- Interobserver variability in reading bump sizes.

- 30% false negatives in active disease

- criteria (Canadian)

            - 5-10mm - HIV+, close contact of active case, fibronodular disease

            - >10mm - everyone else

            - "conversion" - increase in 10mm or more

 

Treatment options:

- Isoniazid (INH) for 9 months

            - best effect, <1% chance of bad liver toxicity

- rifampin for 4 months

            - poorly studied, lots of drug reactions (cyt P450 inducer)

- rifampin+pyrazinamide for 8 weeks

            - serious side effects (5x liver toxicity), rarely used

 

Diagnosis:

Think about it!

- weight loss, fever, chill, night sweats, chronic cough, hemoptysis, fatigue, local symptoms (swollen nodules, headache, dysuria, pleurisy, backache/bone pain, chronic enteritis)

- cultures!!! Molecular tests, radiology, biochemistry, pathology also help

 

TB meningitis

- 1-2% active cases

- high morbidity/mortality even with treatment

- 100% death w/o treatment

- rupture of tubercle causes meningitis

- arachnoiditis at base of brain - vessels, cranial nerves

- typical prodrome of chronic meningitis with headache over 2+ weeks, meningismus, cranial nerve defects, vomiting, confused. Can lead to obtundation, coma, seizures, death

- Stages:

            - 1 - alert

            - 2 - lethargic, CN palsy - 15% mortality

            - 3 - coma, hemiparesis - 90% mortality

- CSF is low yield, always do CXR, chest CT

- if abnormal, sputum cultures

- HIV testing routine if positive for TB, and vice versa

- CSF - low glc, high ptn, mononuclear predominance, low cell count

            - 37% smear positive

            - recommend daily LP x4days (87%)

            - suggest 10-15cc

            - treat while waiting - don't wait

            - cultures can take 7 wks

            - AMTD - amplified myobacteria direct test

                        - molecular testing

                        - still <100+ sensitive

            - culture 60-70% positive

- DDx of tuberculoma - cysticercosis

- early morning gastric aspirates in children

 

Drugs

- INH, pyrazinamide good CNS penetration

- rifampin works in meningitis

- ethambutol, aminoglycosides, quinolones not so good

- INH, rifampin - 9-12 months

- pyrazinamide - 2 months

- corticosteroids - use it for TB meningitis, all stages

            - <25kg - 8mg/kg/d

            - >25kg - 12mg/kg/d

            - taper over at least 3 weeks

- monthly visits, recommended repeat LP and CT scan (paradoxical reactions - often get worse before better)

 

Getting worse?

- image

- reculture - drug resistance?

- adjust steroids

- add at least 2 drugs