The classic triad of meningitis—fever, neck stiffness, and altered mental status is present in <1/2 of adult patients with bacterial meningitis. 95% of the patients have at least two of four symptoms: neck stiffness, fever, headache, and altered mental status (AMS). Infants (especially neonates) and the elderly have an increased risk of meningitis and often have a subtle presentation with nonspecific signs and symptoms (ie AMS, poor oral intact, irritability, seizure). Although fever is the most common symptom it is not always present. Abnormal mental status or seizure plus fever should raise the suspicion of meningitis. A retrospective study of more than 500 children with meningitis found no cases were a single seizure was the sole manifestation of bacterial meningitis. Kernig’s and Brudzinski’s signs are present in <1/2 of adults with meningitis. Purpurae and petechiae may be seen in all causes of bacterial meningitis, especially with N. meningitidis. Due to vaccinations the causes of bacterial meningitis is changing. Currently meningitis in children and adults is due to S pneumoniae (47%), N meningitidis (25%), group B streptococcus (12%), and L monocytogenes (8%). Acute complications include shock, DIC, altered mental status/coma, respiratory distress, seizure, increased ICP, and SIADH. Sequelae following treatment: deafness/hearing loss (10.5%), bilateral severe deafness (5.1%), mental retardation (4.2%), seizure disorder (4.2%), and spasticity or paresis (3.5%).
Work up and Treatment (rapid administration of antibiotics is key)
- Obtain labs and don’t forget the blood and urine cultures
- Based on the need of a head CT before LP (to rule out increased ICP/mass). High-risk features include: new-onset seizures, immunocompromise, papilledema, focal neurologic signs, and impaired consciousness. The need of head CT before LP is a highly debated subject. Remember that a head CT is likely needed at some point as it can identify other disease processes such as encephalitis, brain abscess, and malignancies.
- No CT → Immediate LP…administer antibiotics based on gram stain if rapidly available or start antibiotics empirically
- CT → administer empiric antibiotics…obtain head CT scan…do the LP
- Antibiotics are based on the age of patient and cormorbidities (penicillin and multidrug-resistant strains of S pneumoniae and N meningitidis are becoming more prevalent). A third generation cephalosporin, vancomycin and ampicillin (in the neonate and elderly) are the recommended empiric antibiotics
- Dexamethasone should be given with, or just before, the first dose of antimicrobial therapy
- Consider encephalitis and serious causes of viral meningitis such as HSV in the differential and the need for acyclovir administration
- Send CSF for Gram’s stain and cultures, cell count with differential, glucose, and protein, and other studies as indicated (ie, viral and fungal cultures). Reserve a tube for further testing such as latex agglutination, antigen, PCR and further cultures
- Chemoprophylaxis is recommended for close contacts (households, boyfriend/girlfriend, ect) and for health care workers or others who have been exposed to nasopharyngeal/oral secretions of the patient. Rifampin and single dose ciprofloxacin are the most commonly used chemoprophylaxis in the United States
CSF findings suggestive of bacterial meningitis
- Positive Gram’s stain (positive in 60-90% of cases with specificity of >90%).
- Glucose < 40 mg/dL or ratio of CSF/blood glucose < 0.40
- Protein > 200 mg/dL
- WBC > 1000/μL, 10% may present with a lymphocyte predominance
- Polymorphonuclear neutrophils > 80%
- Opening pressure > than 300 mm
The typical CSF findings may not be present in every patient who has bacterial meningitis and the CSF may have a normal WBC or one with lymphocyte predominance. If meningitis is suspected treat with empiric antibiotics and admit the patient for culture results (positive in 70-85% of cases but < 50% in patients that received prior antibiotics). In low risk children consider using the Bacterial Meningitis Score to predict the risk of bacterial meningitis (see last citation).
…Very dense subject please excuse the length of the post…