Forgacs et al identified findings that are unusual in a patient with chemical meningitis following neurological surgery. The presence of one or more of these findings may indicate a bacterial meningitis. The authors are from Lahey Clinic Medical Center in Burlington, Massachusetts.


Chemical meningitis has all of the following

(1) inflammation in the CSF

(2) negative CSF Gram stain and cultures

(3) recovery without antibiotic therapy


Many cases of chemical meningitis occur with surgery in the posterior fossa. Only a few cases occur after spinal surgery or surgery on the paranasal sinuses.


Findings unusual for chemical meningitis:

(1) temperature > 39.4°C

(2) purulent wound drainage

(3) significant wound erythema and/or tenderness

(4) coma or loss of consciousness

(5) onset of a new seizure disorder

(6) focal neurological signs

(7) CSF rhinorrhea or otorrhea

(8) CSF white blood cell count > 7,500 per µL

(9) CSF glucose < 10 mg/dL


In most patients with chemical meningitis the fever starts within 24 hours of surgery and lasts less than 8 days (page 184).


These features can help identify a group of patients at low risk for bacterial meningitis who do not need antibiotic therapy.


To read more or access our algorithms and calculators, please log in or register.