Lumbar cerebrospinal fluid pulse wave rising from pulsations of both the spinal cord and the brain in humans.

There are two theories regarding the origin of the lumbar cerebrospinal fluid pulse wave (L-CSFPW): that it arises from the arteries supplying the spinal cord, and that it is due to the pulsations of the brain transmitted through the subarachnoid space of the spine. We investigated L-CSFPW of 11 myelopathic patients with a complete (five patients, CB-group) or an incomplete spinal block (six, ICB-group) on myelography to determine the origin of L-CSFPW. Since arterial pressure amplitude (APA), the energy source of L-CSFPW, is not the same between individuals or between before and after operation, not only L-CSFPW itself but also the transfer function between the arterial pressure wave and the L-CSFPW calculated by the system analysis method was analyzed to eliminate the influence of hemodynamic fluctuations. In the system analysis, the arterial pressure wave, L-CSFPW and transfer function were decomposed into five harmonic waves (HW). In the CB group, L-CSFPW was observed to be 0.72 mmHg on average (range, 0.25-1.00) in spite of blocking pulsations of the brain, showing that there was a contribution to L-CSFPW unrelated to the brain, that is, the spinal cord. In the CB group, however, the preoperative transfer function value of HW1 (mean, 0.056; range, 0.012-0.170) was lower than that in the ICB group (mean, 0.137; range, 0.061-0.236) (P < 0.05), indicating that the brain pulsation also contributed to L-CSFPW. In the ICB group, there was significant reduction of HW1 (P < 0.01) and HW2 (P < 0.05) transfer function after posterior decompression surgery in spite of improvement in the subarachnoid space narrowing: preoperative HW1, mean, 0.137, range, 0.061-0.236; postoperative HW1, mean, 0.065, range, 0.021-0.153; preoperative HW2, mean, 0.092, range, 0.011-0.148; postoperative HW2, mean, 0.044, range, 0.030-0.066. It has been reported that the spinal cord blood flow is decreased 20% or more by laminectomy, therefore, L-CSFPW measurement may be sensitive enough to detect a 20% or higher decrease in this flow. This suggests that L-CSFPW could possibly be used clinically as a non-invasive method of monitoring the spinal cord blood flow. For broad clinical application of CSFPW, however, further studies are needed, especially on the direct relationship between CSFPW and spinal cord blood flow itself.