Meningitis

Bacterial Viral ( aseptic) TB Fungal Chemical Parasitic ? Carcinomatous

Meningitis Definition –Bacterial meningitis is an inflammatory response to bacterial infection of the pia- arachnoid and CSF of the subarachnoid space Epidemiology –Incidence is between 3-5 per 100,000 –More than 2,000 deaths annually in the U.S. –Relative frequency of bacterial species varies with age.

Meningitis Epidemiology –Neonates (< 1 Month) Gm (-) bacilli 50-60% Grp B Strep 20-40% Listeria sp. 2-10% H. influenza 0-3% S. pneumo 0-5%

Meningitis Epidemiology –Children (1 month to 15 years) H. influenzae40-60% –Declining dramatically in many geographic regions N. meningitidis25-40% S. pneumo10-20%

Meningitis Epidemiology –Adults (> 15 years) S. pneumo30-50% N. Meningitidis10-35% –Major cause in epidemics Gm (-) Bacilli1-10% –Elderly S. aureus5-15% H. influenzae1-3% –>60 include Listeria, E. coli, Pseudomonas

Meningitis Pathogenesis –Majority of cases are hematogenous in origin –Organisms have virulence factors that allow bypassing of normal defenses Proteases Polysaccharidases

Meningitis Pathology and Pathogenesis –Sequential steps allow the pathogen into the CSF Nasopharyngeal colonization Nasopharyngeal epithelial cell invasion Bloodstream invasion Bacteremia with intravascular survival Crossing of the BBB and entry into the CSF Survival and replication in the subarachnoid space

Meningitis Pathology –Hallmark Exudate in the subarachnoid space Accumulation of exudate in the dependent areas of the brain Large numbers of PMN’s Within 2-3 days inflammation in the walls of the small and medium-sized blood vessels Blockage of normal CSF pathways and blockage of the normal absorption may lead to obstructive hydrocephalus

Meningitis Clinical Manifestations –HA –Fever –Meningismus –Cerebral dysfunction Confusion, delirium, decreased level of consciousness –N/V –Photophobia

Meningitis Clinical Manifestations – Nuchal rigidity –Kernig’s Pt supine with flexed knee has increased pain with passive extension of the same leg –Brudzinski’s Supine pt with neck flexed will raise knees to take pressure off of the meninges Present in 50% of acute bacterial meningitis cases –Cranial Nerve Palsies IV, VI, VII –Seizures

Meningitis Clinical Manifestations - Meningococcemia –Prominent rash Diffuse purpuric lesions principally involving the extremities –Fever, hypotension, DIC –History of terminal complement deficiency –Classic findings often absent Neonates Elderly

Meningitis

Diagnosis –Assess for increased ICP Papilledema Focal neurologic findings –Defer LP until CT scan or MRI obtained if any of above present –If suspect meningitis and awaiting neuroimaging Obtain BC’s and start empiric Abx

Meningitis Papilledema

Obtain CT scan before lumbar puncture in patients with: Immunucompromised state History of CNS disease New onset seizures Papilledema Altered level of consciousness Focal neurologic signs

Obtain blood cultures and give empiric antibiotics if LP is delayed

LP-CSF Tube # 1 Protein & Glucose Tube # 2 Gram stain & Culture Tube # 3 Cell count & differential Tube # 4 Store ( PCR, viral studies etc)

Meningitis Diagnosis –CSF Findings : Opening pressure Appearance Cell count & differential Glucose Protein Gram stain & culture

Opening pressure: high, > 200 mmH20 Cloudy cells/mm3 with a neutrophil predominance of about 80-95% <40mg/dl and less than 2/3 of the serum glucose Protein elevated

Meningitis Diagnosis –Rapid Tests CIE (Counter immunoelectrophoresis/ latex agglut.) PCR –CT/MRI Little role in DIAGNOSIS of menigitis Obtain if suspect increased ICP

Meningitis Diagnosis –Additional Tests CBC w/ diff Blood cultures CXR Electrolytes and renal function

Meningitis Differential Diagnosis –CNS infections (abscess, encephalitis) –Viral/ Tb/ Lyme meningitis –Ricketsial infections –Cerebral vasculitis –Subarachnoid hemorrhage –Neurosyphilis

Meningitis Treatment –Emergent empirical antimicrobial therapy Based on age and underlying disease status –Empiric antibiotic regimines Neonates (<3 months) –Ampicillin plus a third generation cephalosporin Children –Third generation cephalosporin ( alternative -ampicillin and chloramphenicol) Young adults –Third generation cephalosporin (Ceftriaxone) + Vancomycin

Meningitis Treatment –Empiric Antibiotic Regimines Older adults –Ampicillin in combination with third generation ceph. Postneurosurgical Pt’s –Vancomycin plus ceftazidime until cultures are available

Meningitis Treatment –N. Meningitidis High dose Pen G –S. pneumoniae Ceftriaxone For areas with high level resistance –Vancomycin plus third generation cephalosporin or rifampin

Meningitis Treatment –Gm (-) Enterics Third generation cephalosporins –L. monocytogenes Ampicillin –S. aureus Vancomycin or Nafcillin –S. epidermidis Vancomycin

Meningitis Treatment –Duration of Treatment Dependent on infecting organism –Average of days –Gm (-) bacilli for 3 weeks

Meningitis Treatment –Steroids –Shortly before or along with antibiotics. Do not give steroids after antibiotic treatment. –de Gans J, van de Beek D. Dexamethasone in adults with bacterial meningitis. N Engl J Med. 2002;347:

Meningitis Prognosis –Pneumococcal Meningitis Associated with the highest mortality rate –20-30% Permanent neurologic sequelae –1/3 of pts –Hearing loss –Mental retardation –Seizures –Cerebral Palsy

Meningitis Vaccinations –Asplenic pts should have had a pneumoccocal vaccine prior to their splenectomy –Vaccines available for H. influenza –Prophylaxis for N. meningitidis contacts Rifampin

Meningitis Conclusion –Meningitis is an infectious disease emergency –Mortality is often high but can be prevented with appropriate medical therapy –If you consider meningitis in your differential, you are committed to an LP and empiric antibiotics