External Carotid

Figure 2.4. In vivo measurement of blood-brain barrier (BBB) permeability, (a) Internal carotid artery perfusion technique (i) in the rat. Other branches of the carotid artery are ligated or electrically coagulated (o, occipital artery p, pterygopalatine artery). The external carotid artery (e) is cannulated and the common carotid artery (c) ligated. Perfusion time may range from 15 s to 10 min, depending on the test substance. It is necessary to subtract the intravascular volume, Vo, from (apparent volume of distribution), to obtain true uptake values and this may be achieved by inclusion of a vascular marker in the perfusate, for example labelled albumin. Time-dependent analysis of results in estimates of the unidirectional brain influx constant Ki (pi min which is equivalent within certain constraints to the PS product. BBB permeability surface area product PS can be calculated from the increase in the apparent volume of distribution Vd over time. Capillary depletion, i.e. separation of the vascular elements from the homogenate by density centrifugation, can discriminate capillary uptake from transcytosis. (b) i.v. bolus kinetics. The PS product is calculated from the brain concentration at the sampling time, T, and the area under the plasma concentration-time curve, AUC.

Abbreviations CS, carotid artery stenting ECA, external carotid artery. ... 

De Vries P, Sanchez-Lopez A, Centurion D, Heiligers JP, Saxena PR, Villalon CM. The canine external carotid vasoconstrictor 5-HTj receptor blockade by 5-HTm (SB224289), but not by 5-HTm (BRL15572) receptor antagonists. Eur J Pharmacol 1998 362 69-72. 

The carotid bifurcation can be seen in 80% of the adult population at the level of cervical vertebrae 3-5. Distal to the physiologic dilatation of the carotid bulb the internal carotid artery (ICA) proceeds dor-sally to the external carotid artery (ECA) into the petrous bone. Entering the bony carotid canal, it describes a sharp bend and thus causes turbulent flow patterns with somewhat typically symmetrical signal loss on TOF-MRA, which should not be misinterpreted as real stenoses (Fig. 5.2). 

The external carotid artery also starts at the bifurcation. Branches supply the jaw, face, scalp, neck and meninges via the superficial temporal, facial and occipital arteries. 

Fig. 4.1. The anatomy of the arterial circulation to the brain and eye. Gray indentations into the arterial lumen represent sites at which atherothrombosis is particularly common. ACA, anterior cerebral artery EGA, external carotid artery ICA, internal carotid artery MCA, middle cerebral artery PCA, posterior cerebral artery.

The meninges are supplied by branches of the external carotid artery, internal carotid artery and vertebral arteries. The most prominent branches from the external carotid artery are the middle meningeal artery and tributaries of the ascending pharyngeal and occipital arteries. Most of the branches from the internal carotid artery arise near the cavernous sinus and from the ophthalmic artery in the orbit. Branches from the vertebral artery arise at the foramen magnum. There are numerous meningeal anastomoses between these small arteries. 

The scalp is supplied by branches of the external carotid artery, particularly the superficial temporal, occipital and posterior auricular arteries. Above the orbit, there is a contribution from terminal branches of the ophthalmic artery. There is a rich anastomotic network between the various arteries of the scalp. 

Muscular branches of the vertebral artery in the neck. At positions distal to a vertebral obstruction, these muscular branches may receive blood retrogradely from occipital and ascending pharyngeal branches of the external carotid artery, or from the deep and ascending cervical arteries. In addition, anastomoses can develop between branches of the subclavian artery and external carotid artery when the common carotid artery is obstructed. 

Around the orbit. Branches of the external carotid artery can anastomose with branches of the ophthalmic artery if the internal carotid artery is severely stenosed or obstructed. Collateral flow from the external carotid artery into the orbit then passes retrogradely through the ophthalmic artery to fill the carotid siphon, middle cerebral artery and anterior cerebral artery. Sometimes flow may even reach the posterior cerebral artery and vertebrobasilar system. 

Dural anastomoses. These can develop between meningeal branches of the internal carotid artery, external carotid artery and vertebral arteries. Occasionally, small dural anastomoses develop between cortical, leptomeningeal and dural arteries. 

In Japanese, moyamoya means puff of smoke and describes the characteristic radiological appearance of the fine anastomotic collaterals that develop from the perforating and pial arteries at the base of the brain, the orbital and ethmoidal branches of the external carotid artery and the leptomeningeal and transdural vessels in response to severe stenosis or occlusion of one, or both, distal internal carotid arteries (Yonekawa and Khan 2003). The circle of Willis and the proximal cerebral and basilar arteries may also be involved. 

Giant cell arteritis is the most common vascuUtic cause of stroke and is associated particularly with posterior circulation ischemia (Nesher 2000 Ronthal et al. 2003 Eberhardt and Dhadly 2007). Medium and large arteries are affected, especially branches of the external carotid artery, the ophthalmic artery and the vertebral artery. The patients are elderly, with the diagnosis being rare under age 60 years. Malaise, polymyalgia and other systemic symptoms are frequently present. The erythrocyte sedimentation rate is usually raised, often to over 100 mm/h in the first hour. 

Arteriovenous malformations present most commonly with signs consistent with a space-occupying lesion or seizures and consist of an abnormal fistulous connection(s) between one or more hypertrophied feeding arteries and dilated draining veins (Clatterbuck et al. 2005) (Fig. 7.5). The blood supply is derived from one cerebral artery or, more often, several, sometimes with a contribution from branches of the external carotid artery. Arteriovenous malformations vary from a few millimeters to several centimeters in diameter. Approximately 15% are associated with aneurysms on their feeding arteries. Some grow during life but a few shrink or even disappear, and some are multiple. These fistulae occur in or on the brain, or in the dura of the intracranial sinuses. 

Dilated episcleral vessels are a clue to abnormal anastamoses between branches of the external carotid artery and orbital branches of the internal carotid artery, distal to severe internal carotid artery disease. With extreme ischemia, ischemic oculopathy may develop, with impaired visual acuity, eye pain, rubeosis of the iris (dilated blood vessels), fixed dilated pupil, low-pressure glaucoma, cataract and corneal edema. 

Tenderness of the branches of the external carotid artery (occipital, facial, superficial temporal) points towards giant cell arteritis. Tenderness of the common carotid artery in the neck can occur in acute carotid occlusion but is more Ukely to be a sign of dissection, or arteritis. Absence of several neck and arm pulses in a young person occurs in Takayasu s arteritis (Ch. 6). Delayed or absent leg pulses suggest coarctation of the aorta or, much more commonly, peripheral vascular disease. Other causes of widespread disease of the aortic arch are atheroma, giant cell arteritis, syphihs, subintimal fibrosis, arterial dissection and trauma. 

Fig. 12.3. A color-flow Doppler ultrasourid of the carotid bifurcatlori showirig a plaque (arrow) at the origiri of the Iriterrial carotid artery (ICA) arid the resulting stenosis. ECA, external carotid artery CCA, common carotid artery. (See the color plate section.)...

This operation was performed for late carotid rupture following neck trauma in an attempted suicide. The first successful ligation for carotid aneurysm was performed five years later in London by Astley Cooper (Cooper 1836). By 1868, Pilz was able to collect 600 recorded cases of carotid ligation for cervical aneurysm or hemorrhage, with an overall mortality of 43% (Hamby 1952). In 1878, an American surgeon named John Wyeth reported a 41% mortality in a collected study of 898 common carotid ligations, and contrasted this with a 4.5% mortality for ligation of the external carotid artery. 

There were relatively few developments for the next 70 years. However, in 1946, a Portuguese surgeon, Cid Dos Santos, introduced thromboendarterectomy for restoration of flow in peripheral vessels (Dos Santos 1976). The first successful reconstruction of the carotid artery was performed by Carrea, Molins and Murphy in Buenos Aires in 1951 (Carrea et al. 1955). However, this was not an endarterectomy. Rather they performed an end-to-end anastomosis of the left external carotid artery and the distal internal carotid artery (ICA) in a man aged 41 years with a recently symptomatic severe carotid stenosis. 

The preganglionic (second-order) neuron is located in the chest and neck extending from the cervical cord (C8-T2) through the stellate ganglion at the pulmonary apex to the superior cervical ganglion at the bifurcation of the internal and external carotid arteries. 

The study of cerebrovascular disease has advanced markedly in recent years with advances in non-invasive imaging methods such as MR angiography and CT angiography as well as an improved understanding of the immune system in the pathogenesis of atherosclerosis. Atherosclerotic cerebrovascular disease is a common cause of strokes and shows a predilection for sites such as the bifurcation of the common carotid artery into the internal and external carotid arteries and the aortic arch and the major intracranial arteries such as the basilar artery and the middle cerebral arteries. Occlusive atherosclerotic vascular disease of these large extracranial arteries is responsible for as many as 20-30% of ischemic strokes and intracranial steno-occlusive disease causes around 5-10% of ischemic strokes. 

Oral mucosae are composed of multiple layers of cells, which show various patterns of differentiation dependent on the functions of different regions in the oral cavity. The oral mucosa is covered by a stratified, squamous epithelium, and three different types of mucosa can be distinguished the masticatory, the lining, and the specialized mucosa. Blood supply to the oral cavity tissues is delivered via the external carotid artery, which branches to the maxiliary lingual and facial artery. There are no mucus-secreting goblet cells in the oral mucosa, but mucins are found in human saliva. These mucins are water-soluble and form a gel of 10-200 pm thickness. Saliva, mainly composed of water (99%), is continuously secreted in the oral cavity and exists as a film with a thickness of 0.07-0.1 mm. ... 

In the in situ rat-brain-perfusion model of Takasato et al. [7,8], or the modihed Takasato model of Smith [9], the perfusion catheter is placed in the external carotid artery or the common carohd artery, respechvely. In both cases, after ligature of appropriate vessels, one of the cerebral hemispheres is completely perfused via the internal carohd artery. Alternatively other groups insert the infusion cannula in the left cardiac ventricle or in the aorta. These systems ensure perfusion to both hemispheres of the brain [10-12]. 

Ergotamine is a serotonin antagonist, which gives a vasoconstriction of intra- and extra-cranial arteries, above all the external carotid artery, and furthermore intensifies the effects of noradrenaline. 

AR aortic regurgitation CCA common carotid artery ECA external carotid artery ICA internal carotid artery GI gastrointestinal LV left ventricular MR mitral regurgitation PMI point of maximal impulse TR tricuspid regurgitation ... 

Two types of experiments were simulated (i) Bolus Injection. A 02-mL bolus of [ N]ammonia was injected rapidly (02 s) into the right common carotid artery. Based on previously determined recoveries of a diffusible marker, only 85% of the dose was assumed to have reached the brain 22). (ii) Continuous Infusion. [ N]-Ammonia dissolved in physiological saline was infused at a rate of 02 mL/min via the common carotid artery. The external carotid ai ry was ligated so at 80% of the dose was assumed to have reached the brain via the internal carotid artery it was assumed that the remainder was lost via the pterygopalatine artery. 

As a second example of the process that may be followed when modeling the human body with FEA, let us consider blood flow through the carotid artery. This is the main blood supply to the brain (through the internal carotid artery) and is the site of stenoses. Plaque formation (artherosce-losis) narrows the common carotid artery at the origin of the external carotid artery (which flows toward the face) until blood flow is reduced to the brain. 

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