Diagnostic value of cerebrospinal fluid immunoglobulin G (IgG) in pediatric neurological diseases

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.