A total of 71 cerebrospinal fluid (CSF) specimens with paired serum samples from 16 controls and 55 patients with various neurologic diseases ranging in age from 1 to 15 years old were studied using a rate nephelometer to measure their
immunoglobulin G (
IgG) and
albumin levels in both their CSF and serum. The patients included 15 cases of
encephalitis, 6 cases of purulent
meningitis, 20 cases of
aseptic meningitis, 2 cases of
multiple sclerosis and 12 cases of other noninflammatory neurologic diseases. The values of the CSF
IgG quotient,
IgG index, and de novo central nervous system (CNS)
IgG synthesis were then calculated for each subject. In the control group, the mean values were as follows: CSF
IgG, 1.45 mg/dl;
IgG quotient, 6.2%;
IgG index, 0.55; and de novo
IgG synthesis, -1.17 mg/day. Those with CNS inflammatory diseases had significantly higher CSF
IgG levels and
IgG quotients compared with controls (p less than 0.05). The
IgG index was selectively elevated in cases of
encephalitis (p less than 0.005). The values for de novo
IgG synthesis showed significant increase in all types of CNS inflammatory diseases except for the group with
aseptic meningitis. In the noninflammatory diseases, none of the CSF parameters revealed any significant differences from those of the control group. Six cases (40%) of
encephalitis showed normal CSF
protein value, but an abnormal
IgG component,
IgG index and de novo
IgG synthesis. Quantitation of
IgG and other derivatives in CSF gives a sensitive supplementary reference for the detection of
CNS infection.