Absent or minimal cerebrospinal fluid abnormalities in Haemophilus influenzae meningitis

A case of Haemophilus influenzae type b (Hib) meningitis in which the diagnosis and treatment were delayed because of normal cerebrospinal fluid analysis is presented. A retrospective review was conducted at two children's hospitals to determine the frequency and clinical characteristics of patients with Hib meningitis whose spinal fluid had a normal total white blood cell count, normal chemistries, and negative Gram stain, but subsequent growth of Hib in culture. Of 379 cases of Hib meningitis, two had completely normal CSF, and two had CSF containing small numbers of polymorphonuclear cells as the sole abnormality. In three of the four cases, the duration of symptoms was less than 24 hours, and appropriate therapy was significantly delayed because of benign-appearing CSF. Normal CSF cell counts, chemistries, and Gram stain do not exclude the possibility of bacterial meningitis, and one should remain suspicious when a child has clinical findings suggesting meningitis.