Normal Cerebrospinal Fluid Pressure
The normal range for cerebrospinal fluid (CSF) pressure in adults is 6-25 cmH₂O, with a population mean of approximately 18 cmH₂O. 1
Normal Pressure Values
- Adults: 6-25 cmH₂O (with mean ~18 cmH₂O) is the established normal range according to the Infectious Diseases Society of America 1
- Opening pressure ≥25 cmH₂O is defined as elevated and potentially requiring intervention 1, 2
- Pressures ≥250 mmH₂O (approximately 25 cmH₂O) indicate intracranial hypertension requiring urgent clinical attention 3
Clinical Thresholds for Intervention
The Infectious Diseases Society of America provides clear cutoffs for clinical decision-making:
- Normal range: 6-25 cmH₂O - no intervention needed 1
- Elevated: ≥25 cmH₂O - requires clinical attention, particularly with symptoms of increased intracranial pressure or infectious conditions like cryptococcal meningitis 1, 2
- Severely elevated: >40 cmH₂O - indicates severe intracranial hypertension requiring aggressive management 1
- Intermediate range: 180-250 mmH₂O - close monitoring recommended but specific intervention may not be required 3
Measurement Considerations
CSF opening pressure should always be measured when performing a lumbar puncture, except when done in sitting position, as recommended by the Infectious Diseases Society of America 1, 2. This is critical because:
- Opening pressure is typically elevated above 20 cmH₂O in bacterial meningitis 2
- Accurate measurement requires the patient in lateral recumbent position 1, 2
- The reference point for measuring cerebral perfusion pressure should be placed at the external ear tragus 3
Important Clinical Caveats
Low or normal pressure does not exclude certain pathologies:
- In spontaneous intracranial hypotension (SIH), 61% of patients have CSF pressure between 6-20 cmH₂O (technically "normal"), and only 34% have pressure ≤6 cmH₂O 4
- Body mass index and symptom duration significantly influence CSF pressure measurements, with higher BMI and longer symptom duration correlating with higher pressures 5, 4
- Normal CSF pressure should not exclude a diagnosis of SIH if clinical and imaging findings are suggestive 5, 4