 Good day everybody. Dr. Sanjay Sanyal, Professor Department Chair. I'm going to demonstrate the lateral cervical region and all its clinical correlations. Andrea Boundary, sternocleidomastoid. Posterior boundary, the descending fibres of the trapezius. Inferior boundary, clavicle. Most of the clavicle has been removed so therefore this instrument is replacing the clavicle. The roof, investing layer of deep cervical fascia. It not only forms a roof, it also splits to enclose the sternocleidomastoid and the trapezius. And it gets attached to the clavicle and it also gets attached to the manubrium sterni. Here, the investing layer of cervical fascia splits and gets attached to the anterior and posterior margins and in between there's a small space then that is known as the suprasteronal space of burns. Lower of the lateral cervical region. Coming from above downwards, the floor is composed of this muscle that we see here. Splenius capitis. The next muscle, this one, levator scapulae. The third muscle, scalinus medius. The fourth muscle, scalinus anterior. All these muscles are covered by another layer of deep cervical fascia which is known as a pre vertebral fascia. So that constitutes the floor. Apex of the triangle is where the sternocleidomastoid and the attachment of the trapezius meet. The sternocleidomastoid is attached to the mastoid process and to the lateral half of the superior nuclei. The trapezius is attached to the medial half of the superior nuclei and the external occipital protuberance. So the meeting point of the two is the apex of the triangle. And the base of the triangle is the middle one third of the clavicle. So these are the boundaries of the lateral cervical region. The sternocleidomastoid is an oblique and the largest muscle of the neck. The inferior attachment is to the medial sterni and to the clavicle. That's why it is called sternocleidomastoid. And the insertion I have already mentioned. The sternocleidomastoid action is to tilt the head to the same side and turn the chin and the face to the opposite side. The sternocleidomastoid is supplied by this nerve which is called the accessory nerve. And we can see the accessory nerve coming from the jugular foremen. This is the accessory nerve. It is coming from the jugular foremen. It is traveling laterally and it's supplying the sternocleidomastoid from deep inside. And then as it comes down, it comes out, travels through the lateral cervical region and it disappears under the descending fibers of the trapezius. So therefore the accessory nerve supplies both the muscles. There is a very important clinical correlation pertaining to the sternocleidomastoid and that is known as tauticolus. Tauticolus is when there is a contracture or contraction of the sternocleidomastoid and there are two types of tauticolus. One is congenital which happens during childbirth. Some injury to the fibers of the sternocleidomastoid can produce fibrosis and growth. A tumor-shaped structure and that is known as a congenital tumor of the sternocleidomastoid and that will result in the child having a head tilted to one side. That is congenital tauticolus. There is another condition related to that called fibrometrosis coli. In contrast, there is something called acquired tauticolus. That occurs in adults on those who are taking neuroleptics medication and as an adverse reaction to that, which is known as extra-perimodal reaction, they can have spasmodic contraction of the sternocleidomastoid and or the trapezius alternately on each or both sides. And that is known as spasmodic tauticolus or cervical dystonia, which is a side effect of extra-perimodal reaction of anti-psychotic medication. The sternocleidomastoid also touches the chin to the chest when both the sides are acting together. And so therefore this forms the basis of one of the tests whereby we give resistance under the chin and ask the person to touch the chest. For unilateral testing, we put the hand on one cheek and give resistance and ask the patient to turn his head. And that will be a test for one side. And yet one more action of the sternocleidomastoid is it produces an extension of the neck at the atlantooccipital joint. And finally, the sternocleidomastoid, because it is attached to the fevicul, it also acts as an accessory muscle of respiration. It assists in the pump-handle movement of the chest wall. Action of the dysentic fibrosis trapezius is to shrug the shoulder or elevate the shoulder upwards. And therefore, if there is injury to the spinal accessory nerve, this movement will be paralyzed and the shoulder will be drooping down. Of course, the shrugging movement of the shoulder will be partially compensated by the levator scapulae and the superior fibres of the sedatus anterior. This is the levator scapulae. I wanted you to notice something very unique about the course of the spinal accessory nerve. As it is emerging from under the sternocleidomastoid, it emerges under the posterior border of the sternocleidomastoid at the junction of the upper one-third and the lower two-third of the sternocleidomastoid. It travels on the surface of the levator scapulae muscle, along with the superficial branch of the transverse cervical artery. And we can see it is disappearing under the anterior but border of the descending fibres of the trapezius at the junction of the upper two-thirds and lower one-third. This is the unique course of the spinal accessory nerve. Spinal accessory nerve is prone to injury in injury or knife slash injury of the lateral cervical region. This is a content of the lateral cervical region. This is the external jugular vein. As you can see, it is running on the surface of the sternocleomastoid. In this particular patient, it is very prominent. Normally, it is not so prominent. But in a normal person, we can see the external jugular vein when the person is straining or doing vascular maneuver. This extra jugular vein is formed by the union of the posterior division of the retromandibular vein and the posterior auricular vein, which comes out from the perotted gland. This is the posterior auricular vein. The extra jugular vein runs on the surface of the sternocleomastoid. When it reaches the lateral cervical region, it pierces the investing layer of deep cervical fascia and then it opens at right angles to the subclavian vein. The external jugular vein is accompanied by some lymph nodes in this region and they are known as superficial cervical lymph nodes which receive lymph from the periservical collar. And the superficial cervical lymph nodes then drain into the deep cervical nodes. The external jugular vein can also be injured in knife slash injury to the lateral cervical region. And this is prone to air embolism because of two reasons. Number one, as it pierces the investing layer of cervical fascia, the margins are attached to the cervical fascia. And therefore, they remain open. They do not contract and retract. So therefore, it sucks in air. And the second reason is Bernoulli's principle because the external jugular vein opens into the subclavian vein at right angles. There is relatively low pressure here. So therefore, it sucks in air. Coming to the tributaries of the external jugular vein. We see one tributary here. This is the transverse cervical vein. This is the suprascacular vein. And there is another tributary that comes from the anterior cervical region and meets here. That is known as anterior jugular vein. The tributaries are transverse cervical, suprascacular, and anterior jugular vein, formed by the union of the submental veins. Coming to the nerves in the lateral cervical region, we see one nerve here. This is the lesser occipital nerve, C23. It is coming from the cervical plexus. And the cervical plexus is located here in the sternocular mastoid. There's another nerve which runs like this. This is the great auricular. The great auricular also is C23 ventral ramai. It supplies the perotid, the perotid sheath, the lobular of the ear, the skin in front of the ear, the skin in the lower part of the pinna and a little bit of the skin behind. That is the great auricular. Lesser occipital supplies in the posterior part of the scalp. All of them are C23 ventral ramai. Then we have these two fibres that we can see which are curved. These are the transverse cervical. They come out from behind the posterior part of the sternocular mastoid. They curve like this. They travel in the superficial fascia. They pierce the platysma and they supply the skin of the anterior cervical region. And finally, we have these bundle of nerves that we can see coming down. These are the supraclavicular nerves. The supraclavicular nerves, as they descend down, they break up into three sets of fibres. Lateral, intermediate and medial. And they supply the skin in this region. The supraclavicular nerves can be injured in this case of fascia clavicle. And rarely, the supraclavicular nerves can even pierce through the clavicle. At this juncture, I need to mention an important point and that is known as nerve point. This bundle of cervical plexus nerves which are coming out from behind the posterior margin of the sternocular mastoid, this region of the sternocular mastoid is called the nerve point of the neck. This nerve point of the neck can be identified by two methods. One, it is at the junction between the upper half of the sternocular mastoid and the lower half of the sternocular mastoid. So the mid point of the posterior border is the nerve point. The other way of locating the nerve point is a vertical line dropped from the mastoid process which is where my index finger is located. A vertical line dropped to the clavicle. The mid point of the line also corresponds to the nerve point. This is the place where if we inject anesthetic agent in sufficient quantity, we can anesthetize a large portion of the lateral cervical region, anterior cervical region and a portion of the scalp. The next nerve which comes out from the cervical plexus is this nerve which I picked up here. This is the phrenic nerve C345. This runs in front of the skeleton's anterior muscle and it goes behind the subclavian vein. In small percentage of people, the fifth root of the phrenic nerve is absent, in which case they can get a contribution from the nerve to the subclavius. Remnant of the subclavius is visible here and the nerve to the subclavius is C5 and that gives a contribution which runs in front of the subclavian and it meets with the phrenic nerve which is going behind the subclavian. And in such people, the subclavian vein can be injured because it can be trapped within a loop by the main phrenic nerve and the accessory phrenic nerve contributed by the nerve to the subclavius. Thank you for watching. Stay tuned for the next video.