Hello all this is Dr Alsup and we will be discussing the carpal tunnel in this video
so we are getting into a tunnel. And even if you haven't studied anatomy before you've
likely heard of the carpal tunnel, usually in association with carpal tunnel syndrome so
you may have heard somebody say I have carpal tunnel well we all have a carpal tunnel
they're typically saying I have carpal tunnel syndrome. And so we're going to take the anatomical
concepts and apply them to how they present in carpal tunnel syndrome, this is a really excellent
example of understanding anatomy and how that helps understand clinical presentations. But we're
going to start with even what is the carpal tunnel. Well it has carpal in its name which is a hint we
should think in the wrist region likely involving carpal bones both of which are true. The carpal
tunnel is going to be located in the anterior wrist with the floor created by the carpal bones
it almost forms on like a kind of bowl-like structure and it's going to have a ligament
forming the roof and really creating the tunnel through which things travel. And this specific
ligament is called the transverse carpal ligament and very often you also hear it referred to as
the flexor retinaculum, these are the same thing, transverse carpal ligament flexor retinaculum.
Now let's discuss what will be the contents of the tunnel and by far what is making up the bulk of
the contents are those long flexor tendons whose muscle muscle bellies are located in the anterior
compartment of the forearm, so specifically we're talking the flexor digitorum superficialis tendons,
the flexor digitorum profundus tendons, and you even have the flexor pollicis longus tendon
traveling through the tunnel often off to its kind of on its own but still within the tunnel.
The tendons are surrounded importantly by tendon sheaths and it's not as visible in
this illustration they're better represented on the next slide but recall that tendon sheaths
are elongated bursa like structures that are going to surround tendons.
So the tendons and tendon sheaths take up almost all the space within the carpal tunnel.
But also traversing the tunnel is the median nerve and it just got done innervating most of those
muscles in the anterior compartment of the forearm but its work is not done and it needs to make
its way to the hand to provide both sensory and motor innervation to particular parts of the hand.
Of note just before the carpal tunnel there is a cutaneous branch of the median nerve which is
called the polymer cutaneous branch that's going to branch just proximal to the carpal
tunnel or just before the carpal tunnel, and we will get to why that's important in a moment.
Now let's talk a bit about why this anatomical area is something you need to be familiar with
and this is carpal tunnel syndrome. Carpal tunnel syndrome most commonly occurs when there is an
increase in size of some of the contents of the tunnel such as what can occur with inflammation
of the tendon sheaths which is kind of a form of bursitis so you can see the tendon sheets in this
image here that are surrounding the tendons. These can increase in size and can become inflamed this
can be due to infection, fluid retention, excessive or overly repetitive actions of the flexor muscles
and this importantly can cause the compression of the median nerve within the carpal tunnel,
which will affect median nerve branches that branch off within the carpal tunnel or just distal
to the carpal tunnel. So carpal tunnel syndrome can present as kind of tingling or diminished or even
completely absent sensation in the medial 3.5 digits, so digit one remember is the thumb
then two, three, and then you have a little bit of digit four and it does not affect the
sensation associated with a lot of the palm, it can you know some of those branches can extend
a little bit further down so you think more in terms of the proximal palm but also importantly
in terms of the thenar eminence that area would the skin over the thenar eminence would typically
not be affected unless you had a high median or before or proximal to the carpal tunnel lesion.
All right so also importantly the median nerve also has a motor branch that innervates the thenar
compartment hand muscles so the muscles in the thenar compartment and so these are going to all
be associated with the first digit and so it's going to have a few actions that are going to be
affected but really opposition is one that you can easily test to see if that's being affected
so opposition of the thumb. And it can be loss of strength or even a loss of coordination in the
in those actions. With prolonged expression of this syndrome there can be atrophy in the muscles of
the thenar compartment. All right excellent we have reached the summary slide and I hope you
are becoming more familiar with the big picture anatomical concepts related to the carpal tunnel.
I thank you for your time and attention here and always feel free to reach out with any questions