Clinical Case - Posterior Triangle of the Neck
A 65-year-old man presented in his physician's office complaining of frequent headaches focused primarily on the right side and a series of four episodes of transient dysfunction involving the left side of his body during the last two months. These episodes involved progressive symptoms, beginning with only numbness in his left hand during the first episode, muscle weakness in his left arm and left leg during the second and third episodes, and limb weakness accompanied by slurred speech during the fourth episode. Auscultation of the neck indicated a bruit present on the right side. An arteriogram revealed ulcerated stenosis of the right carotid bifurcation and mild left-sided carotid stenosis. The patient was advised that he should undergo a carotid endarterectomy immediately in order to prevent an otherwise imminent stroke. The patient submitted to the surgery, which was performed without incident, and has experienced no further headaches or episodes of left-sided dysfunction.
Questions to consider:
- What are bruits and what causes them in the neck?In this context, a bruit is a systolic murmur heard only in the neck. It is caused by turbulent and noisy blood flow over a roughened surface (i.e. an atherosclerotic plaque).
- What is an arteriogram and how is it obtained?An arteriogram is a radiograph demonstrating the course and lumen diameter of an artery and its tree. Arteriograms are obtained via x-ray imaging after a injection of a radiopaque contrast medium into the arterial tree.
- What is an endarterectomy?An endarterectomy is a surgical procedure for removing an occlusion from an artery. This type of surgery is often used to remove threatening atherosclerotic lesions from arteries such as the carotid and coronary arteries. The procedure involves excision of the intima and plaque and part of the media of the artery in order to leave a smooth surface.
- What structures are particularly vulnerable to damage due to their presence in or near the carotid sheath when an endarterectomy is performed?The vagus nerve and its branches (the superior laryngeal and an aberrant recurrent laryngeal), the hypoglossal nerve, the mandibular branch of the facial nerve, the ansa cervicalis, the accessory nerve, and the internal jugular vein are all vulnerable to damage during an endarterectomy. In addition, some arteries and veins are routinely divided during this surgery (including the facial vein, sternocleidomastoid artery and vein, and the superior thyroid artery). Injuries to the glossopharyngeal nerve, branches of the cervical plexus (transverse cervical and great auricular), the brachial plexus (due to stretching), the phrenic nerve, and the cervical sympathetic plexus have also been reported in the literature. The moral to this story is that the anatomy of this region is extremely complex and great care must be exercised in performing this sort of procedure.
- Why were the patient's symptoms generally transient and not permanent?The transience of the patient's symptoms could be linked to a number of things, including arterial spasm, transient thrombosis, and the like. All of these things will likely have an amplified effect if the carotid artery is already severely stenotic. The effects of the ischemia of the brain are not permanent because many of the instigators (i.e. arterial spasm) are reversible, and because, as long as the lesion is at the level of the carotid bifurcation and is unilateral, collateral circulation in the brain provided by the circle of Willis, if adequate, will keep the ischemic region at least partially perfused.
- Where do atherosclerotic lesions usually form in the carotid arteries?The most common location for atherosclerotic plaque formation is at the bifurcation or branch points of arteries, in the case of the carotid arteries it is at the carotid bifurcation.
W.H. Baker. Diagnosis and Treatment of Carotid Artery Disease. 1985.
R.M. Greenhalgh, L.H. Hollier. Surgery for Stroke. 1993.
Caplan L. Diseases of the carotid system. Primary Care; Clinics in Office Practice. 6(4):717-32. 1979 Dec.
After observing the procedure many times and numerous attempts on cadavers, you are called on to perform a subclavian catheterization on a critically ill adult patient in order to monitor her central venous pressure. An infraclavicular approach on the right side is chosen.
Questions to consider:
- Where is the subclavian vein located?The subclavian vein is found in the lower part of the omoclavicular or subclavian triangle. It is the continuation of the axillary vein, beginning at the lower border of the first rib. It crosses the clavicle just medial to the midclavicular point and proceeds superiorly and arches over the first rib anterior to the anterior scalene muscle before turning posteriorly again and descending into the thorax.
- What surface anatomical landmarks are critical for guiding infraclavicular subclavian catheterization?The midclavicular point and the lower border of the clavicle are critical for locating the subclavian vein for venipuncture. In addition, the suprasternal notch is used to aim the needle once it is inserted under the clavicle.
- Describe the relationships of the subclavian vein with other neurovascular structures in the vicinity.The subclavian vein is the most anterior neurovascular structure in the subclavian triangle. Posterior to it at the first rib is the anterior scalene muscle, which separates the vein from the subclavian artery and the inferior trunk of the brachial plexus. Just medial to the first rib, the subclavian vein is joined by the internal jugular vein before proceeding into the thorax to join with the brachiocephalic vein from the other side to form the superior vena cava. On the left side, the thoracic duct empties into the left subclavian vein at its junction with the internal jugular.
- Why might a right-sided approach be preferred to a left-sided one for subclavian catheterization?A right-sided approach is preferred because laceration of the thoracic duct, which empties into the left subclavian vein, can be avoided by catheterization on the right side.
- Based on your knowledge of anatomy, identify several potential complications associated with subclavian catheterization.Potential complications to subclavian catheterization include pneumothorax, hemothorax, cardiac tamponade, bacterial infection or sepsis, and brachial plexus injuries.
You have been asked to assess the post-operative condition of a 65 year old man who has been surgically treated for carcinoma of the tongue. Since the tumor was in its early stages, the surgeon has performed a left-sided hemiglossectomy with block dissection of the left neck. In this operation all posterior triangle lymph nodes were removed, along with other structures. The patient was recovering well and was able to move.
Questions to consider:
- Which important nerve is likely to be injured in posterior neck triangle operations? How would you test for its integrity post-operatively?The accessory nerve (XI) is likely to be injured in such an operation. Its injury in the posterior triangle will cause paralysis of the trapezius muscle. The usual clinical test for assessing the integrity of the nerve is by asking the patient to shrug his/her shoulder.
- What other structures are important to consider in such operations?Upper and middle trunks of the brachial plexus; third part of the subclavian artery and suprascapular nerve and artery, and branches of the cervical plexus.
- What groups of lymph nodes might the surgeon remove from the posterior triangle?Supraclavicular lymph nodes are relatively important, (they are part of the deep cervical lymph nodes); other less important nodes are the occipital situated at the apex of the triangle.
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