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Carotid sinus
Arteries of the neck. The carotid sinus is at the origin of the internal carotid artery.
Details
Artery	Carotid artery
Nerve	Branch of glossopharyngeal nerve to carotid sinus
Identifiers
Latin	sinus caroticus
MeSH	D002346
TA98	A12.2.04.008 A12.2.06.003
TA2	4367
FMA	50094
Anatomical terminology[edit on Wikidata]

In human anatomy, the carotid sinus is a dilated area at the base of the internal carotid artery just superior to the bifurcation of the internal carotid and external carotid at the level of the superior border of thyroid cartilage. The carotid sinus extends from the bifurcation to the "true" internal carotid artery. The carotid sinus is sensitive to pressure changes in the arterial blood at this level. It is the major baroreception site in humans and most mammals.

Structure

The carotid sinus is the reflex area of the carotid artery, consisting of baroreceptors which monitor blood pressure.

Function

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The carotid sinus contains numerous baroreceptors which function as a "sampling area" for many homeostatic mechanisms for maintaining blood pressure. The carotid sinus baroreceptors are innervated by the carotid sinus nerve, which is a branch of the glossopharyngeal nerve (CN IX). The neurons which innervate the carotid sinus centrally project to the solitary nucleus in the medulla of the brainstem. The solitary nucleus indirectly modulates the activity of sympathetic and parasympathetic neurons in the medulla and pons through the hypothalamus. These neurons then regulate the autonomic control of the heart and blood vessels. The aortic arch baroreceptors are innervated by the aortic nerve (nerve of Cyon, Ludwig nerve), which combines with CN X (vagus nerve) and travels to the NTS.

Clinical significance

It is a sensitive site of the body because stimulation can drive large-scale reflex effects throughout the body. This can be used therapeutically in treatment of resistant hypertension by baroreflex activation. Physical assault at this point, producing massive baroreflex activation can cause dramatic falls in blood pressure and cerebral ischemia. This is the mechanism of baroreflex activation therapy.

Disease

The carotid sinus often has atherosclerotic plaques because of disturbed hemodynamics (low wall shear stress, flow reversal/recirculation). Since these plaques, if large and unstable, predispose to ischemic strokes and transient ischemic attacks, carotid endarterectomies are frequently done for prophylaxis.

Carotid sinus hypersensitivity

The carotid sinus baroreceptor can be oversensitive to manual stimulation from the pressure applied at the carotid sinus at the carotid bifurcation. It is a condition known as 'carotid sinus hypersensitivity' (CSH), 'carotid sinus syndrome' or 'carotid sinus syncope', in which manual stimulation causes large changes in heart rate and blood pressure, which can result in bradycardia, vasodilation, and hypotension. This classically presents as a patient who has "fainted" (actually a presyncope) on several occasions while shaving, or in some other way coming into contact with their carotid sinus. Denervation is performed as treatment for this.

Usually older patients with syncope and unexplained falls often have coexisting conditions such as carotid sinus hypersensitivity, orthostatic hypotension, and vasovagal syncope.

Carotid sinus syndrome

Carotid sinus syndrome (CSS) is a temporary loss of consciousness that sometimes accompanies convulsive seizures because of the intensity of the carotid sinus reflex when pressure builds in one or both carotid sinuses.

Treatment of resistant hypertension

Stimulation of baroreceptors at the carotid sinus can be used to treat resistant hypertension via activation of the baroreflex. A pacemaker-like device can be implanted to electrically stimulate the receptors chronically, which is found to lower blood pressure by 15–25 mmHg.

Massage

Massage of the carotid sinus, carotid sinus massage is used to diagnose carotid sinus syncope and is sometimes useful for differentiating supraventricular tachycardia (SVT) from ventricular tachycardia. Like the valsalva maneuver, it is a treatment for acute SVT. It is less effective than pharmaceutical management of SVT with verapamil or adenosine, but it is still the preferred first line of treatment in a hemodynamically stable patient.

Carotid sinus reflex death

Carotid sinus reflex death is a potential etiology of sudden death in which manual stimulation of the carotid sinus allegedly causes strong glossopharyngeal nerve (Vagus nerve is for aortic arch baroreceptors) impulses leading to terminal cardiac arrest. Carotid sinus reflex death has been pointed out as a possible cause of death in cases of strangulation, hanging and autoerotic strangulation, but such deductions remain controversial. Medical literature examining the use of carotid sinus massage involving brief gentle pressure of the carotid sinus in therapeutic settings as a diagnostic and therapeutic examination tool have reported few potentially fatal complications. A carotid massage can also possibly dislodge a thrombus, or some plaque. This could lead to any number of life-threatening effects, including stroke.

In martial arts and self defense

Stimulation of the carotid sinus via a slap or a strike, to induce (usually temporary, but sometimes lethal) loss of consciousness is a self-defense technique, and is often taught in martial arts such as karate.

See also

• Baroreflex
• Carotid body

References

1. Pellerito JS, Polak JF (2012). Introduction to vascular ultrasonography. Saunders/Elsevier. ISBN 9781437714173. OCLC 797855544.
2. Câmara R, Griessenauer CJ (January 2015). "Chapter 27 - Anatomy of the Vagus Nerve". In Tubbs RS, Rizk E, Shoja MM, Loukas M (eds.). Nerves and Nerve Injuries. San Diego: Academic Press. pp. 385–397. doi:10.1016/b978-0-12-410390-0.00028-7. ISBN 978-0-12-410390-0.
3. Hermanowicz N (January 2007). "Chapter 13 - Cranial Nerves IX (Glossopharyngeal) and X (Vagus)". In Goetz CG (ed.). Textbook of Clinical Neurology (Third ed.). Philadelphia: W.B. Saunders. pp. 217–229. doi:10.1016/b978-141603618-0.10013-x. ISBN 978-1-4160-3618-0.
4. ^ Scheffers IJ, Kroon AA, Schmidli J, Jordan J, Tordoir JJ, Mohaupt MG, et al. (October 2010). "Novel baroreflex activation therapy in resistant hypertension: results of a European multi-center feasibility study". Journal of the American College of Cardiology. 56 (15): 1254–1258. doi:10.1016/j.jacc.2010.03.089. PMID 20883933.
5. Glagov S, Zarins C, Giddens DP, Ku DN (October 1988). "Hemodynamics and atherosclerosis. Insights and perspectives gained from studies of human arteries". Archives of Pathology & Laboratory Medicine. 112 (10): 1018–1031. PMID 3052352.
6. Kharsa A, Wadhwa R (2024). "Carotid Sinus Hypersensitivity". StatPearls. Treasure Island (FL): StatPearls Publishing. PMID 32644485. Retrieved 2024-03-23.
7. ^ Wijetunga MN (2021-10-16). Talavera F, Compton SJ (eds.). "Carotid Sinus Hypersensitivity: Background, Pathophysiology, Epidemiology". Medscape.
8. Tan MP, Chadwick TJ, Kerr SR, Parry SW (June 2014). "Symptomatic presentation of carotid sinus hypersensitivity is associated with impaired cerebral autoregulation". Journal of the American Heart Association. 3 (3): e000514. doi:10.1161/JAHA.113.000514. PMC 4309040. PMID 24947997.
9. Wallbach M, Koziolek MJ (September 2018). "Baroreceptors in the carotid and hypertension-systematic review and meta-analysis of the effects of baroreflex activation therapy on blood pressure". Nephrology, Dialysis, Transplantation. 33 (9): 1485–1493. doi:10.1093/ndt/gfx279. PMID 29136223.
10. Lim SH, Anantharaman V, Teo WS, Goh PP, Tan AT (January 1998). "Comparison of treatment of supraventricular tachycardia by Valsalva maneuver and carotid sinus massage". Annals of Emergency Medicine. 31 (1): 30–35. doi:10.1016/S0196-0644(98)70277-X. PMID 9437338.
11. Ballo P, Bernabò D, Faraguti SA (August 2004). "Heart rate is a predictor of success in the treatment of adults with symptomatic paroxysmal supraventricular tachycardia". European Heart Journal. 25 (15): 1310–1317. doi:10.1016/j.ehj.2004.05.011. PMID 15288158.
12. Field JM, Ruple J, eds. (2007). "Managing Stable Tachycaradia: the ACLS Tachycardia Algorithm". Advanced Cardiac Life Support Provider Manual. American Heart Association. p. 98. ISBN 978-0-87493-496-0.
13. Greenwood RJ, Dupler DA (August 1962). "Death following carotid sinus pressure". JAMA. 181 (7): 605–609. doi:10.1001/jama.1962.03050330035007. PMID 13901589.
14. Deepak SM, Jenkins NP, Davidson NC, Bennett DH, Mushahwar SS (November 2005). "Ventricular fibrillation induced by carotid sinus massage without preceding bradycardia". Europace. 7 (6): 638–640. doi:10.1016/j.eupc.2005.06.006. PMID 16216770.
15. Vilke GM (2007). "Neck Holds". In Ross DL, Chan T (eds.). Sudden Deaths in Custody. Springer Science & Business Media. ISBN 978-1-59745-015-7.
16. Passig K. "Carotid sinus reflex death - a theory and its history". Datenschlag. Archived from the original on 4 May 2012. Retrieved 28 February 2006.
17. Mankikar GD, Clark AN (May 1975). "Cardiac effects of carotid sinus massage in old age". Age and Ageing. 4 (2): 86–94. doi:10.1093/ageing/4.2.86. PMID 1146669.
18. Sensei B (8 November 2013). "Carotid Sinus strike/slap as an effective self defense technique". Full Potential Martial Arts. Retrieved 30 May 2015.

Additional images

• Carotid sinus

External links

• lesson5 at The Anatomy Lesson by Wesley Norman (Georgetown University) (livingneck)

• Arteries of the head and neck