Measuring CSF flow dynamics in spontaneous intracranial hypotension with phase-contrast magnetic resonance imaging: Potential implications for diagnosis and treatment

Abstract

Certain magnetic resonance (MR) techniques are flow sensitive, and phase-contrast magnetic resonance imaging (PC-MR) has been utilized both qualitatively and quantitatively to evaluate cerebrospinal fluid (CSF) flow in a variety of clinical conditions (1). Although spontaneous intracranial hypotension (SIH) is, by definition, a disorder of CSF homeostasis typically resulting from a spinal CSF leak, PC-MR has been studied very little in this setting. An initial case report in 2004 first documented decreased systolic and diastolic CSF flow volume at the level of the cerebral aqueduct using PC-MR in a patient with SIH (2). Although confined to a single patient, the findings were compelling because normalization was documented following resolution of SIH. A number of years elapsed before a more systematic study of PC-MR in SIH was completed when Hasiloglu et al. showed a change in CSF flow dynamics in 25 SIH patients compared with controls and further related the PC-MR findings to clinical findings and opening pressure (3). The manuscript entitled Usefulness of PhaseContrast Magnetic Resonance Imaging for Diagnosis and Treatment Evaluation in Patients with SIH by Tung et al. is a welcome addition to the existing body of literature (4). The discriminating power of some of the measured CSF flow parameters at the level of the cerebral aqueduct rivals that of the more widely accepted anatomic imaging features of SIH. Moreover, there may be potential for PC-MR to identify SIH patients who lack characteristic MR findings such as dural enhancement. The change in CSF flow witnessed with treatment suggests that PC-MR may also be beneficial for monitoring patient progress during treatment for SIH. The authors point out that results with PC-MR are known to vary in subjects in relation to age, sex, body mass index, cardiac function, and technical parameters (i.e. velocity encoding gradient, anatomic site, MR scanner, etc.). As a result, the impact of these variables will need to be more fully defined in SIH patients, as has been conducted for healthy subjects. Appropriately, the authors also recognize multiple potential technical limitations in their study. However, moving forward, a number of considerations unique to the use of PC-MR in SIH patients will need to be considered. Although correlation of CSF flow dynamics with patient symptoms and validated imaging findings in SIH is useful, a quantifiable relationship with opening pressure would be preferred. No lumbar punctures were performed in the current study to allow for correlation of opening pressure with CSF flow dynamics as measured by PC-MR (4). When patient presentation and imaging findings strongly suggest headache due to SIH, it is increasingly common in clinical practice to forego lumbar puncture for opening pressure measurement. Indeed, this approach is also endorsed in the International Classification of Headache Disorders, 3rd edition (beta version), which states that dural puncture to directly measure CSF pressure is not necessary in patients with positive MR findings (5). However, it would be ideal for future research studies using PC-MR in SIH to report opening pressures as much as possible. Applying PC-MR to SIH is a relatively new application of existing technology. Hasiloglu et al. demonstrated a significant positive correlation between opening pressure and multiple CSF flow parameters (CSF flow