Cerebrospinal fluid opening pressure in clinical practice - a prospective study.

BACKGROUND: Measurement of CSF opening pressure (CSFOP) is valuable and much used in the investigation of several neurological conditions. However, there are different opinions regarding reference values and influence of age, gender and body mass index (BMI). We have, in a previous study, noted possible differences in CSFOP between gender and age groups. Here the aim was to collect information regarding normal distribution of CSFOP in an out-patient sample and also include BMI. METHODS: We collected CSFOP from a lumbar puncture, following a standardized procedure, performed in an ordinary neurological out-patient sample. Age, gender and BMI was also registered. Descriptive statistics and linear regression was used. RESULTS: 339 patients with a normal distribution of age and BMI were included consecutively (60% females). We found a mean CSFOP of 17.5 H2O (range 4.0-30.0). In multivariable linear regression, age, gender and BMI all independently affected CSFOP. Male gender (ß = 1.5, p = 0.002), lower age (ß = - 0.095, p < 0.001) and higher BMI (ß = 0.42, p < 0.001) were all associated with higher CSFOP. CONCLUSION: Using two standard deviations, we provide suggestions for CSFOP limits with respect to gender, age and BMI. Our results suggest that CSFOP cut-offs for pathological intracranial hypertension should be raised with these factors taken into consideration. As a "rule-of-thumb" we suggest the following cut-offs: for males < 30 cm H2O (< 25 if over age 70), and for females < 25 cm H2O (27.5 if over 30 BMI). A diagnosis of intracranial hypertension should not be given without such considerations.