For clinically applied anatomy, let’s think
about a specific type of lung tumor called
a pancoast tumor. A pancoast tumor is a tumor
of the lung that will occupy the posterior
thoracic wall and grow upwards along the posterior
thoracic wall and start to invade and involve
some neurologic structures in and around the
subclavian artery. One such structure here
that’s involved or may be involved is the
stellate ganglion. As mentioned previously,
the stellate ganglion results from the fusion
of the inferior cervical ganglion and the
first thoracic ganglion. This is, again, part
of the sympathetics and if it continues to
grow, it can also involve some of the inferior
roots of the brachial plexus, for example,
T1 and even C8.
If there is neural involvement of pancoast
tumor with the stellate ganglion, you’ll
inhibit the sympathetics and as a result of
that, the individual will have ptosis, drooping
of the eye lid, myosis as well as anhidrosis.
Anhidrosis is an absence of sweating. If there
is neurologic involvement in the inferior
roots of the brachial plexus, the individual
will have some sensory loss along the T1 and
C8 dermatomal levels which would be the medial
forearm and would have weakness of the intrinsic
muscles of the hand.
Cardiac referred pain helps us to apply some
of the anatomy that we just went through.
As you recall, the spinal cord levels for
the preganglionic sympathetic neurons were
housed where T1 to T4 may be even, as well
as the T5. So, if you have pain coming from
the heart through the afferents going back
into those spinal cord levels, the neurologic
processing confuses that with the sensory
fibers that are coming from those dermatomes on the skin.
And so, you will involve the T1 down to T4
dermatomal levels that will then continue
on into the medial aspects of the arm and
even forearm as well as the anterior part
of the chest. This is showing the back, but
the nipple is an excellent landmark here to
help you understand where your dermatomes
would lie anteriorly. The nipple lies within
the T4 dermatome, so the other dermatomes
would lie above that. So, if there is crushing
pain and referred pain to the left upper chest,
that’s radiating also into the medial arm
and medial forearm, that would be somewhat
typical of cardiac referred pain, but I think
the general rule of thumb is to say that cardiac
referred pain can be more than what is typical
and there are gender differences as well,
as cardiac referred pain has been known to
radiate upwards into the jaw and also, can
radiate to the back.
Now, we have the important take-home messages
from this presentation.
The phrenic, the vagus conveying the parasympathetics
and the sympathetics innervate thoracic viscera.
The phrenic nerves are motor and sensory to
The parasympathetics conserve and restore
because of their tremendous influence on the
GI system to process nutrients and to absorb
nutrients and to decrease the heart rate whereas
sympathetics do the opposite. They elicit
the fight or flight response, so they will
increase the heart rate, increase the force
of contraction and make us more responsive
to these fight or flight events.
Sympathetic preganglionic fibers originate
from spinal cord segments T1 to as well as
T5 when we look at innervation to thoracic
viscera. These then will synapse some postganglionic
neurons that reside in the ganglia of the
sympathetic trunks and then from there, the
post ganglionic axons are distributed to the
Pharmacologic stimulation of the sympathetics
is efficacious in promoting bronchodilation
during asthmatic attacks.
A pancoast tumor may produce neurologic symptoms
due to involvement of the inferior roots of
the brachial plexus and/or stellate ganglion.
And lastly, cardiac referred pain may be explained
by the dermatomes associated with the segmental
And thank you for joining me on this lecture
of the nerves of the thorax.