From the Guidelines
The normal range for opening pressure, specifically intracranial pressure, is between 10 to 20 cmH2O (or 80-200 mmH2O) in adults, as measured in the lateral recumbent position. This range is crucial for diagnosing and managing various neurological conditions. According to the provided evidence, increased intracranial pressure (ICP) may be present early in the course of certain diseases, such as coccidioidomycosis, with pressures of 180–250 mm H2O being concerning but not necessarily requiring immediate intervention 1.
Key Considerations for Opening Pressure Measurement
- The measurement should be taken with the patient relaxed, legs extended, and not holding their breath or straining, as these actions can artificially elevate the pressure.
- Obesity can increase opening pressure, with values up to 25 cmH2O sometimes considered normal in obese individuals.
- Pressures above the normal range may indicate conditions such as idiopathic intracranial hypertension, meningitis, encephalitis, or intracranial mass lesions, while pressures below normal might suggest CSF leakage or dehydration.
Clinical Implications
- The measurement of opening pressure is important diagnostically as it helps differentiate between various neurological conditions and guides treatment decisions.
- In the context of coccidioidomycosis, managing increased ICP may involve removal of CSF to reduce pressure, with the goal of lowering it to 50% of the opening pressure or 200 mm of H2O, whichever is greater, and repeating this process until the pressure stabilizes to <250 mm H2O 1.
- It is essential to measure the opening pressure before removing any CSF to obtain an accurate reading, which is critical for guiding further management and intervention.
From the Research
Normal Range for Opening Pressure
The normal range for opening pressure, also known as intraocular pressure or intracranial pressure, can vary depending on the source and methodology used.
- According to a study published in 2014 2, the normal range of intracranial pressure (ICP) measured by lumbar puncture in adults is 6 to 25 cmH2O, with a population mean of about 18 cmH2O.
- Another study published in 2019 3 found that the mean opening pressure was 155.4 mmH2O, with a 95% reference interval of 82-242 mmH2O.
- A 2021 study 4 aimed to identify subjects with normal cerebrospinal fluid pressure and found that a score based on certain parameters, including obesity, can help identify patients with normal or elevated CSF opening pressure.
- A 2014 study 5 compared optic nerve sheath diameter with ICP measured by opening pressure manometry on lumbar puncture and found that an opening pressure of greater than or equal to 20 cm H2O was considered elevated.
- A 2022 study 6 characterized the features of elevated lumbar puncture opening pressure in aseptic meningitis patients and found that a pressure greater than 25 cm H2O was documented as elevated.
Factors Influencing Opening Pressure
Several factors can influence opening pressure, including:
- Age: Increasing age was associated with lower opening pressure 3.
- Body mass index (BMI): Higher BMI was associated with higher opening pressure 3, 6.
- Obstructive sleep apnea (OSA): OSA was more likely to occur in patients with higher opening pressure 3.
- Obesity: Obesity was a significant predictor of elevated CSF opening pressure 4.