Nejm 2006;354:44; 2004;351:1849

Cause:

(Nejm 1997;337:970) of adult meningitis:

• Age 20-60 yr: 1st pneumococcus, 2nd Neisseria meningitidis(Serogroup Y > C > B > A), 3rd listeria; rarely now, Haemophilus influenzae
• Age 60+ yr: 1st pneumococcus, 2nd listeria, 3rd others

Pathophys:

Meningococcal: IgA protease on surface distinguishes infectious from commensal meningococcus (Nejm 1992;327:864). Impaired protein C activation in sepsis (Nejm 2001;345:408)

URI leads to bacteremia 1st, then

• Metastatic infections of meninges, eye, pericardium, joints, and/or cardiac valves
• Immune complex arthritis without permanent damage

Meningococcal: serogroup A in epidemics in developing countries; rare in US, 1/100 000/yr or <3000 cases/yr; groups B, Y, and C are sporadic and in epidemics in US (Jama 1995;273:383, 390)

From respiratory tract of carriers (<3% of general population) or patients with meningococcal pneumonitis. Increased after influenza infection. Bacteremia recurs in patients with complement deficiencies of C'₆, C'₇, or C'₈. (40% of all adult meningitis is nosocomial, often gram negatives, although meningococcal never is)

Incr by exposure to tobacco smoke

Sx:Fever, changed affect/mental status (85%), stiff neck, headache (95% have at least 2/4)

Si:Fever >100°F (95%), stiff neck (88%), petechial rash with central focal necrosis (66%) (purpura fulminans) (pictures—Nejm 1996;334:1709), focal neurologic deficits (28%), seizures (23%)

Without rx, death in hours; w rx, 25% meningococcal mortality; pneumococcal mortality higher and morbidity >50%

• CNS thrombophlebitis with focal seizures and deficits, cranial nerve neuropathies (Nejm 1972;286:882), communicating hydrocephalus
• Meningococcal myocarditis in 75% at postmortem, 20% have aseptic pericardial effusions (Ann IM 1971;74:212)
• Adrenal hemorrhage and insufficiency (Waterhouse-Friderichsen syndrome w meningococcal)
• Chronic meningococcal bacteremia without CNS involvement, fever, or rash

In compromised host, r/o listeria, cryptococcus, toxoplasmosis, and other treatable causes of meningitis

Lab:Bact:CSF has >10 white cells/mm³, usually (87%) >200, mostly polys; glucose <40 mg % (50%); protein >45 mg % (96%), usually >100 mg %; Gram stain, CSF culture (for meningococcal, best in 10% CO₂), blood cultures

Xray:CT scan if focal si's before LP (Nejm 2001;345:1727), but START ANTIBIOTICS 1ST

Rx:

Prevent meningococcal in epidemic or in endemic areas by (Nejm 2006;355:1466):

• Decreasing intimate contact
• Immunizing with quadrivalent conjugated (Menactra) (Med Let 2005;47:29) for age 11-55 yr, or unconjugated (Menomune) (Med Let 2000;42:69) for under 11 yr or over 55 yr, vaccine 0.5 cc sc × 1; vs serogroups A, C, Y, and W-135; 85% effective in epidemic but under age 3 yr immunogenicity less (Jama 2001;285:177); used in epidemics, routinely in army, and in dorm-living college students, espdorm-living freshmen (Jama 2001;286:688); $82/dose
• Administering prophylactic antibiotics to family, day care companions, and close friends, not school or hospital personnel unless 2 cases occur in a school (Jama 1997;277:389): 1st, ciprofloxacin 500 mg po × 1; 2nd, rifampin 600 mg po qid × 2 d; or ceftriaxone

of acute unknown adult meningitis:

• Cefotaxime or ceftriaxone pending cultures, w vancomycin up to 4 gm qd to cover resistant pneumococcus. With sensitivities, can truncate to penicillin 24 million U iv qd in q 2 h bolus × 1 d then q 4 h for meningococcal type and covers 64% of pneumococcus as well (Nejm 1997;337:970) or can add vancomycin to cover resistant pneumo until cultures back; doesn't eliminate carrier state; same choices in head trauma since most likely organism is pneumococcus; rarely chloramphenicol if penicillin-allergic, but alarming appearance of chloro-resistant meningococcus appearing (Nejm 1998;339:868) in developing countries. Over age 50-60 yr, include ampicillin to cover listeria.
• Dexamethasone 10 mg q 6 h × 4 d probably improves outcomes (Nejm 2002;347:1549) in all types of bacterial meningitis (ACP J Club 2010;53:JC2-11 vs 2003;138:60) if dx’d by Gram stain or culture (Nejm 2007;357:2431, 2441, 2507)

of other Gram negatives: cefotaxime, ceftizoxime, or ceftriaxone for nonpseudomonas types but not listeria (requires 3 wk penicillin). Ceftazidime and gentamicin for pseudomonas. Ampicillin + chloramphenicol or ceftriaxone or cefotaxime for H. flu, and drop the 2nd drug if organism turns out to be ampicillin-sensitive