Y. Takahashi et al., NEURAL CONNECTION BETWEEN THE VENTRAL PORTION OF THE LUMBAR INTERVERTEBRAL DISC AND THE GROIN SKIN, Journal of neurosurgery, 85(2), 1996, pp. 323-328
This study was designed to investigate neural mechanisms of referred p
ain in lumbar intervertebral disc lesions. Patients with a degenerativ
e disc in lower lumbar segments occasionally complain of groin pain, w
hich cannot be explained anatomically as having a radicular origin. In
rats pretreated with intravenous application of Evans blue dye, the d
ye extravasation appeared in the groin skin after application of capsa
icin to the ventral portion of the L5-6 intervertebral disc. This resp
onse occurred even in rats with a sectioned L-5 spinal nerve and sympa
thetic trunks, but did not occur in rats with a sectioned genitofemora
l nerve. Capsaicin topically applied to the sciatic nerve did not caus
e dye extravasation in the hindpaw. Therefore, groin dye extravasation
was not due to a direct effect of capsaicin but, rather, presumably w
as caused by an ''antidromic axon reflex'' of dichotomizing C fibers o
r to a segmental sympathetic reflex causing vascular permeability. The
present results indicate that the ventral portion of the lumbar discs
is neurally connected to the groin skin via the upper (L-2) lumbar sp
inal nerves in rats. Groin pain coincident with low-back pain may be e
xplained as referred pain, indicating that a lesion is present in the
ventral portion of the lumbar intervertebral disc space.