From the Guidelines
A normal lumbar puncture (LP) opening pressure in adults typically ranges from 10 to 20 cmH2O (or 100-200 mmH2O) when measured in the lateral recumbent position. For children, the normal range is slightly wider, approximately 10-28 cmH2O 1. These measurements should be taken with the patient lying on their side with legs flexed, as position significantly affects cerebrospinal fluid (CSF) pressure. Obesity can elevate opening pressures, with values up to 25 cmH2O sometimes considered normal in obese individuals. Opening pressures above these ranges may indicate conditions such as idiopathic intracranial hypertension, meningitis, or intracranial mass lesions, while pressures below 6 cmH2O might suggest CSF leakage or volume depletion, as noted in the context of intracranial hypotension 1. The pressure reading should be obtained before removing any CSF for testing, as fluid removal will artificially lower the pressure. Accurate measurement requires the patient to be relaxed, as anxiety, pain, or abdominal compression can transiently elevate CSF pressure and lead to false readings.
Some key points to consider in the measurement and interpretation of LP opening pressure include:
- The importance of patient position during measurement, with the lateral recumbent position being standard 1.
- The potential for obesity to affect normal pressure ranges, with higher pressures sometimes considered normal in obese individuals.
- The significance of pressures outside the normal range, which may indicate various pathological conditions such as intracranial hypertension or hypotension 1.
- The need for careful measurement technique to avoid false readings, including ensuring the patient is relaxed and that the measurement is taken before any CSF is removed for testing.
Given the most recent and highest quality evidence available, the normal range for LP opening pressure is generally considered to be between 10 to 20 cmH2O. This range is supported by various studies and guidelines, including those focused on the management of conditions that may affect intracranial pressure, such as cryptococcal meningitis 1 and the diagnosis of intracranial hypotension 1.
From the Research
Normal LP Opening Pressure
- The normal range of intracranial pressure (ICP) measured by lumbar puncture (LP) in adults is 6 to 25 cmH2O (95% confidence intervals), with a population mean of about 18 cmH2O 2.
- However, there is considerable variability, and some normal individuals may have pressures of 30 cmH2O or higher, emphasizing the need to interpret pressure measurements in the clinical context 2.
- A study on aseptic meningitis found that the mean normal lumbar puncture opening pressure (LPOP) was 16.13 cmH2O (SD = 4.15) 3.
- Another study on normal pressure pseudotumor cerebri reported a mean CSF opening pressure of 11 cmH2O (ranging from 9 to 15 cmH2O) during the first LP, and 7.3 cmH2O (ranging from 6 to 10 cmH2O) during the second LP 4.
- The effect of body position on lumbar cerebrospinal fluid opening pressure has been studied, with one study finding a mean pressure of 178.54 mmH2O in the flexed position and 160.52 mmH2O in the relaxed position 5.
- Another study found no statistically or clinically significant difference in CSF opening pressure between the prone and lateral decubitus positions, with a mean OP of 26.5 cmH2O in the prone position and 27.7 cmH2O in the lateral decubitus position 6.