Are changes in intracranial pressure detectable by measurement of the cerebrospinal fluid velocity wave speed in the spinal canal?
Contents
Personel
The problem
Craniospinal compliance has been thought to be an important indicator of craniospinal health. Some have postulated that, when properly functioning, the spinal subarachnoid space (SAS) compliance may act as a notch filter to dampen out cerebrospinal (CSF) flow pulsations16,17. However, a non-invasive technique for assessment of craniospinal compliance has not been validated. The proposed pilot study aims to investigate the sensitivity of a novel non-invasive MR technique to changes in intracranial pressure (ICP), which is directly related with craniospinal compliance.
Communication between the intrathorasic and ICP due to postural changes4,6, coughing20, valsalva and Queckenstedt’s test, and abdominal pressure2 has been well documented9,20,22,23. These pressure changes are transmitted from the abdomen into the CSF system (ICP) through the dural venous sinuses and epidural venous plexus (Figure 1 and Figure 2). Thus, it is possible to vary ICP and compliance by a number of non-invasive tests. The changes in ICP are expected to be detectable by spinal CSF velocity wave speed, since the spinal canal forms a compliant tube-like system which transmits cranial CSF pulsations through the spinal SAS (~1 cc per cardiac cycle at C2 level15,18).
Hypothesis and research objectives
We hypothesize that the spinal CSF velocity wave speed is indicative of ICP which can be modified non-invasively by a series of tests. The goal of this research is thus to validate the sensitivity of a novel MR protocol to changes in ICP.
Methods and study outline
- A. in vivo MR measurements.
Our approach is to obtain CSF velocity wave speed measurements using the technique described by Kalata et al.10 on healthy male 20-30 year old subjects under two conditions.
- Baseline MR CSF velocity wave speed measurements10 will be obtained on the subject at normal pressure in the supine position.
- A series of three tests will be performed on the subject while obtaining identical MR measurements as the baseline measurement. The three tests will include continuous positive airway pressure (CPAP)3, Queckenstedt’s test9,20,22,23, and placement of a mass on the stomach. The CPAP and Queckenstedt’s test will be performed at moderately elevated pressures (i.e. ~15 cm H2O). A mass will be placed on the stomach (i.e. 10 Kg water bags). The subject’s heart rate and or transcutaneous carbon dioxide tension, PCO2, will be monitored. Subjects will be able to discontinue testing at any time. A medical doctor will be present throughout the duration of testing.
- The baseline measurement and all three tests will initially be conducted on three subjects to determine which are best suited to change CSF velocity wave speed in the spinal subarachnoid space. Subsequent tests will be performed using the most promising tests.
- B. Single-blind processing of MR data.
CSF velocity wave speed in the spinal canal for each subject will be obtained from the MR study data using the technique employed by Kalata et al. 10 and Filden et al.7. These calculations will be performed by an engineer blinded to the test case.
Expected results and potential impact
The proposed work will determine if the non-invasive MR test is sensitive to changes in ICP caused by a series of tests. If proven efficacious, it could be further explored to understand its sensitivity and accuracy, and could have the potential to provide a clinically useful tool for assessment of craniospinal compliance.
Preliminary results
References
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