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.