THE ORIGIN AND SIGNIFICANCE OF SPINAL-CORD PULSATION

We studied the origin and mechanism of spinal cord pulsation in ten do gs in order to elucidate its clinical significance. Under general anes thesia, a 6 cm length of the animals' cervical spinal cord was exposed and the cerebrospinal fluid removed. The amplitude of spinal pulsatio n was then measured by means of ultrasonography in Mode M. The measure ments were made after the spinal cord was cut: (1) on the cranial side ; (2) on the cranial as well as caudal side, with the nerve roots and radicular arteries intact; (3) on both sides as in (2), which was then supplemented with the severance of the nerve roots and radicular arte ries. It was demonstrated that, while the pulsation amplitude stood at an average of 88.0 mu m before the surgical treatment, it rose to 455 .0 mu m in (1) and 274.8 mu m in (2), but dropped to nearly zero in (3 ). The 5.2-fold increase in pulsation following the cordotomy on the c ranial side was attributed to two factors: (1) the increased spinal mo bility due to the cordotomy; (2) the elevation of blood pressure. The results of the three different degrees of spinal detachment suggested that spinal pulsation derived mainly from the radicular arteries and t hat its presence indicated low tonicity in the spinal cord and favorab le circulation in the radicular arteries.