Injuries of nerves and their consequences - Reflex Sympathetic ...

J24 INJURIES OF NERVES.
the sacral plexus and its greater sciatic branch are the
nerve tissues most liable to serious injury, and it is usually
to compression of this latter nerve that we must look
for an explanation of such cases of infra-pelvic palsy as
follow labor, and are due to this physical cause.
Bianchi asks, very shrewdly,
if it be not also possible
that compression of the sympathetic iilaments may have
some influence in predisposing the uterus to the congestions
and inflammations which occasionally follow delivery.
Considering the well-known efltect, in this direction,
of sections of vaso-motor nerves in the abdomen and
thorax, I myself should be disposed to attribute far more
to this possible cause of disease than has hitherto been
done.
While it is clear from the cramps so common in labor
that the nerves are frequently compressed,
it is also plain
that this compression is rarely adequate to a graver result,
and the chief reason for this is to be found in the anatomical
arrangements of the pelvis. The sciatic nerves,
resting as it were in deep gutters, the projection of the
sacro-vertebral spine* tends to ward ofl' from them the
pressure of the foetal head, "-while the sacral nerves resting
ao^ainst the back wall of the excavation are in some dei^free
saved, owing to the fact that the inclination of the planes
and axes of the bassin, direct against the anterior walls
and symphysis pubis the principal eftects of the greatest
pressure of the fcetal head."t
I may add to these remarks that the pelvic nerves have
remarkably thick sheaths; that, like other nerves, they
endure a good deal of squeezing and pressure without
lasting injury, and finally, that, as Bianchi has shown, it
is usually the forceps, rather than the head alone, which
is at fault. Indeed, he has been unable to discover any
* Bianchi, p. 40. f Ibid