When is an opening pressure lumbar puncture (LP) important?

From the Guidelines

An opening pressure measurement during a lumbar puncture (LP) is crucial when evaluating conditions that may affect cerebrospinal fluid (CSF) pressure, particularly in cases of suspected increased intracranial pressure, such as idiopathic intracranial hypertension, meningitis, encephalitis, subarachnoid hemorrhage, or suspected CSF leaks. The measurement of opening pressure is essential for diagnosing and managing these conditions, as it helps to distinguish between communicating and non-communicating hydrocephalus, monitor treatment effectiveness, and guide therapeutic decisions. According to the 2016 Infectious Diseases Society of America (IDSA) clinical practice guideline for the treatment of coccidioidomycosis 1, increased intracranial pressure (ICP) may be present early in the course of disease, and pressures of 180–250 mm H2O are concerning, but do not require specific intervention, while pressures ≥250 mm H2O define the need for urgent or emergent intervention. Some key points to consider when measuring opening pressure include:

• Measuring the pressure with the patient in a lateral recumbent position with legs extended to obtain accurate readings
• Aligning the manometer with the spinal needle hub
• Ensuring the patient is relaxed, as Valsalva maneuvers, anxiety, or pain can artificially elevate the pressure
• Normal opening pressure ranges from 10-20 cmH2O (or 100-200 mmH2O) in adults, with values above 25 cmH2O generally considered elevated
• The pressure should be lowered by removal of CSF in a volume sufficient to reduce the pressure to 50% of the opening pressure or 200 mm of H2O, whichever is greater, in cases of increased ICP 1. It is also important to note that clinical assessment, rather than cranial CT, should be used to determine if it is safe to perform a LP, unless there is a clinical contraindication indicating possible raised intracranial pressure due to or causing brain shift 1. In summary, measuring opening pressure during a lumbar puncture is a critical step in evaluating and managing conditions that may affect CSF pressure, and should be performed in accordance with established guidelines and protocols.

From the Research

Importance of Opening Pressure Lumbar Puncture

• The opening pressure lumbar puncture (LP) is important in diagnosing and managing idiopathic intracranial hypertension (IIH) 2, 3.
• It is used to measure the pressure of the cerebrospinal fluid (CSF) in the spinal canal, which can help diagnose IIH and monitor its progression 4.
• A high opening pressure LP is a key diagnostic criterion for IIH, with a pressure exceeding 250 mmH2O considered abnormal 3.
• However, some patients with IIH may have a normal or low opening pressure LP, making diagnosis and management more challenging 3, 5.

Clinical Applications

• Therapeutic lumbar punctures may be used to manage headache in IIH patients, although the benefit is often small and temporary 5.
• The procedure can also help reduce papilledema and improve visual outcomes in some patients 2.
• Opening pressure LP can be used to monitor the effectiveness of treatment and adjust management strategies as needed 6.

Factors Influencing Opening Pressure

• Body mass index (BMI) is a significant factor influencing opening pressure, with higher BMIs associated with higher pressures 4.
• Age is also a factor, with younger individuals tend to have higher opening pressures 4.
• Other factors, such as obstructive sleep apnea, may also contribute to variations in opening pressure 4.

Limitations and Controversies

• The use of opening pressure LP as a therapeutic measure in IIH is controversial, and its effectiveness is still debated 2, 5.
• The procedure can cause complications, such as post-lumbar puncture headache, which can be severe and prolonged 5.
• Further research is needed to fully understand the role of opening pressure LP in diagnosing and managing IIH, and to develop more effective and safe treatment strategies 6.