B-waves in cerebral and spinal cerebrospinal fluid pulsation measurement by magnetic resonance imaging

Noninvasive measurement of B-waves is possible by magnetic resonance (MR) imaging using echo planar imaging (EPI) sequences. In this study, the proportion of B-waves in the cerebrospinal fluid (CSF) of the spinal canal and in the aqueductus cerebri was evaluated under normal and pathologic conditions, respectively. The proportion of the influence of pulse and respiration on the CSF pulsations was estimated.

The spinal CSF was evaluated in 7 volunteers at 5 spinal levels (C1, C2/3, C 6/7, T5, and T12). Examination of the CSF frequencies at the aqueduct was performed in 14 volunteers, 10 patients with normal pressure hydrocephalus, and 5 patients with an aqueductal stenosis. An EPI sequence was applied at 1.5 T. During the 8-minute measurement time, pulse and respiration were coregistered. A MATLAB routine analyzed the spectral portion of the B-waves and the pulse- and respiration-dependent frequencies of the CSF.

The amount of B-waves was small in cerebral (2.5%) and spinal measurements (3.4%) but significantly higher in the spinal CSF (P < 0.001). There was no statistically different amount of B-waves in the aqueduct for volunteers and hydrocephalic patients and between the different spinal levels in healthy volunteers. Spinal measurements revealed a rising portion of respiration-related frequencies from C1 to T12, whereas the portion of pulse-related frequencies declined.

The data support that B-waves are a physiologic phenomenon. They can be delineated in the spinal and cerebral CSF. A higher amount of spinal B-waves reflects a stronger venous and respiratory influence.