In this lecture, we’re going to look at the
nerve lesions of the upper limb. So we’re
going to have an initial overview of the nerve
supply to the upper limb and then look at
some typical location of the lesions, and
how this leads to motor and sensory deficits.
We’re going to look at some nerves that
we’ve already covered in the course, so
the musculocutaneous, the median and the ulnar
nerves. And the radial, axillary and long
thoracic nerves. So here we can see just
on the screen on this
right-hand side, we can see that we have the
overview of the brachial plexus and the three
cords coming away from the brachial plexus,
the medial posterior, and lateral cord, how
the medial and the lateral cord give rise to
the musculocutaneous, the median, and the
ulnar nerves, and how the posterior cord gives
rise to the radial and the axillary nerve.
So we’re going to look at those specific
nerves and how damage to those nerves can
lead to sensory and motor deficits. It’s
important to appreciate that coming
off the brachial plexus, we have a whole series
of cutaneous nerves that come either from
the brachial plexus itself or come from one
of those five terminal branches, and they
supply the skin of the upper limb, as we spoke
about in one of the first lectures.
We can see here various regions of the upper limb
and how they are supplied by various nerves.
So let’s start by looking at the musculocutaneous
nerve. Remember, the musculocutaneous nerve,
as we can see on the screen here, is involved in
supplying muscles within the anterior compartment
of the arm. So damage to the musculocutaneous
nerve which can happen as a penetrating injury
within the axilla, maybe during a fight perhaps,
damage to the musculocutaneous nerve can lead
to paralysis of the muscles it supplies. So
remember, it supplies coracobrachialis, it
supplies biceps brachii, and it supplies brachialis.
And if the musculocutaneous nerve is damaged,
then, therefore, these muscles are not going
to have their innervations. So they will become
paralyzed. The effect of that is,
well, if you appreciate
the effect of these muscles contracting on the
elbow joint and on the radio-ulnar joints,
then you can appreciate that damage to the
musculocutaneous nerve will lead to weakened
flexion at the elbow, and also weakened supination
of the forearm. So damage to the musculocutaneous
nerve can lead to a weakening of the elbow
flexion and a weakening of supination.
Sensory loss, well, if you look at damage to
the musculocutaneous nerve, then via the
lateral cutaneous nerve of the forearm, you
have sensory loss over the lateral arm.
And we can see here in this region, the musculocutaneous
nerve gives rise to the lateral cutaneous
nerve of the forearm. So you may well have
sensory loss on this region of the forearm.
This nerve that we can see running along here,
the lateral cutaneous nerve of the forearm
is originating from the musculocutaneous nerve.
So damage here would lead to loss of sensation.