Reference range for cerebrospinal fluid opening pressure in children.

We conducted a 2-year, single-center prospective study of CSF opening pressure in children undergoing lumbar puncture as part of their routine clinical care. Our objective was to establish a useful, clinically relevant reference range for opening pressure and a threshold value for abnormally elevated opening pressure (in the 90th percentile or higher, defined a priori). Our reference group consisted of children between 1 and 18 years of age, none of whom was taking a medication or had signs of a disease or condition that would alter opening pressure on lumbar puncture (e.g., papilledema, hydrocephalus, cerebral edema, Chiari malformation, meningitis, or use of diuretics). The procedure was performed with subjects in the lateral recumbent position, and the opening pressure was measured with the use of a standard manometer. (For enrollment criteria, methods, and results, see the Supplementary Appendix, available with the full text of this letter at NEJM .org.) Reference-range parameters for opening pressure were determined with the use of standard descriptive statistics, whereas associations between age, BMI, and depth of sedation were determined using linear regression analysis.