From the Guidelines
An opening pressure of 37mm water after a lumbar puncture in a sitting position is considered low, not high. Normal opening pressure in the sitting position typically ranges from 80-180mm water [ 1 ]. The lower value of 37mm water could indicate low cerebrospinal fluid (CSF) pressure, which might be associated with conditions such as CSF leaks, dehydration, or excessive CSF drainage. Some key points to consider in the management of patients with low CSF pressure include:
- Increased fluid intake
- Caffeine
- Bed rest
- In persistent cases, procedures such as blood patches may be necessary It's essential to interpret this finding in the clinical context of the patient's symptoms and other diagnostic findings. If a patient with this measurement is experiencing headaches that worsen when upright and improve when lying down, this would be consistent with intracranial hypotension. In contrast, elevated intracranial pressure is a concern in conditions like cryptococcal meningitis, where an opening pressure above 25 cm of CSF (or approximately 250 mm water, considering 1 cm of CSF is roughly equal to 10 mm water) is considered high and may require interventions such as lumbar punctures to reduce pressure [ 1 ]. However, the provided value of 37mm water is significantly below these thresholds, suggesting a different clinical concern.
From the Research
Opening Pressure Values
- The opening pressure of 37mm water after lumbar puncture in a sitting position can be considered high, as elevated intracranial pressure (ICP) is defined as a cerebrospinal fluid (CSF) opening pressure (OP) greater than 25 cmH2O 2.
- To put this value into perspective, a study found that the median CSF opening pressure in patients with idiopathic intracranial hypertension was 33.0 cmCSF 3.
- Another study reported a case of a patient with idiopathic intracranial hypertension who had a lumbar puncture showing a moderately high opening pressure of 35 cm H2O 4.
Comparison to Normal Values
- A normal opening pressure is typically considered to be below 25 cmH2O 2.
- In a study, the CSF drop rate median was 23 drops/30 seconds in patients with normal OP, while it was 47 drops/30 seconds in patients with raised OP 2.
- The analysis through ROC showed an AUC of 0.980, with a sensitivity of 100% and a specificity of 91% if chosen as a limit, 29 drops in 30 seconds 2.
Clinical Significance
- Elevated intracranial pressure can be a significant clinical concern, and accurate measurement of opening pressure is crucial for diagnosis and management 2, 3.
- The therapeutic effect of a single lumbar puncture in idiopathic intracranial hypertension remains unclear, but it may have a moderate effect on ophthalmological outcomes 3.
- Patients with idiopathic intracranial hypertension must be monitored carefully, and shunting should be considered if intracranial pressure is high 4.