Internal stenosis

Clinical trials and meta-analyses have demonstrated that early carotid endarterectomy (CEA) is the preferred treatment for most patients with severe symptomatic internal carotid artery (ICA) stenosis and selected patients with moderate disease.However, CEA is often delayed in chnical practice, or may not be appropriate in some patients due to an unfavorable risk-benefit profile. In these settings, it is reasonable to consider acute antithrombotic treatment to prevent early recurrent stroke. 

Dissection of the internal carotid and vertebral arteries is a common cause of stroke, particularly in young patients. Although many occur due to trauma, it is estimated that over half occur spontaneously. The mechanism of stroke following arterial dissection is either by artery-to-artery embolism, by thrombosis in situ, or by dissection-induced lumenal stenosis with secondary cerebral hypoperfusion and low-flow watershed infarction. Occasionally, dissection may lead to the formation of a pseudoaneurysm as a source of thrombus formation. Vertebrobasilar dissections that extend intracranially have a higher risk of rupture leading to subarachnoid hemorrhage (SAH). ° ... 

Suwanwela N, Can U, Furie KL, Southern JF, Macdonald NR, Ogilvy CS, Hansen CJ, Buonanno FS, Abbott WM, Koroshetz WJ, Kistler JR Carotid Doppler ultrasound criteria for internal carotid artery stenosis based on residual lumen diameter calculated from en bloc carotid endarterectomy specimens. Stroke 1996 27(11) 1965-1969. 

Erickson SJ, Mewissen MW, Foley WD, Lawson TL, Middleton WD, Quiroz FA, Macrander S J, Lipchik EO. Stenosis of the internal carotid artery assessment using color... 

Polak IF, Dobkin GR, O Leary DH, Wang AM, Cutler SS. Internal carotid artery stenosis accuracy and reproducibility of color-Doppler-assisted duplex imaging. Radiology 1989 173(3) 793-798. 

Warfarin has not been adequately studied in non-cardioembolic stroke, but it is often recommended in patients after antiplatelet agents fail. One small retrospective study suggests that warfarin is better than aspirin.30 More recent clinical trials have not found oral anticoagulation in those patients without atrial fibrillation or carotid stenosis to be better than antiplatelet therapy. In the majority of patients without atrial fibrillation, antiplatelet therapy is recommended over warfarin. In patients with atrial fibrillation, long-term anticoagulation with warfarin is recommended and is effective in both primary and secondary prevention of stroke.12 The goal International Normalized Ratio (INR) for this indication is 2 to 3. 

Coronary artery bypass graft surgery Thoracic surgery whereby parts of a saphenous vein from a leg or internal mammary artery from the arm are placed as conduits to restore blood flow between the aorta and one or more coronary arteries to bypass the coronary artery stenosis (occlusion). 

Bockenheimer SA, Mathias K. Percutaneous transluminal angioplasty in arteriosclerotic internal carotid artery stenosis. AJNRAmJ Neuroradiol 1983 4 791-792. 

Anderson CM, Lee RE, Levin DL et al. (1994) Measurement of internal carotid artery stenosis from source MR angiograms. Radiology 193 219-226... 

Fig. 15.2. Diffusion-weighted imaging in a 54-year-old patient with acute onset of severe left-sided hemiplegia shows a territorial infarction in the right middle cerebral artery territory, as well as additional bilateral hemodynamic lesions. Ultrasound examination in this patient showed high-grade internal carotid artery stenosis on both sides...

Fig. 15.5. As in this 68-year-old man with a high-grade stenosis of the left internal carotid artery presenting with a fluctuating mild left-hemispheric syndrome, acute ischemic lesions can affect all areas considered to be hemodynamic risk zones...

Fig. 15.13. A 76-year-old woman with a subtotal stenosis of the left internal carotid artery shows no sufficient collateral flow and only faint flow signal in the left middle cerebral artery (upper row), severe hypoperfusion (time-to-peak maps) of the left middle cerebral artery territory (middle row) and small acute hemodynamic stroke lesions on DWI (bottom row). The patient was later successfully treated with carotid endarterectomy...

Del Sette M, Eliasziw M, Streifler JY et al (2000) Internal borderzone infarction a marker for severe stenosis in patients with symptomatic internal carotid artery disease. Stroke 31 631-636... 

Traon AP, Costes-Salon MC, Galinier M et al. (2002). Dynamics of cerebral blood flow autoregulation in hypertensive patients. Journal of Neurology Science 195 139-144 van der Grond J, Eikelboom BC, Mali WPThM (1996). Flow-related anaerobic metabolic changes in patients with severe stenosis of the internal carotid artery. Stroke 27 2026-2032... 

Fig. 6.1. Digitally subtracted arterial aragiogram showing a severe stenosis of the internal carotid artery.

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. 

Low flow may occur secondary to systemic hypotension, as during cardiac arrest. This results in bilateral infarcts, usually in the posterior boundary zones, and causes cortical blindness, visual disorientation and agnosia, and amnesia. Alternatively, a relatively small fall in systemic blood pressure in the presence of internal carotid occlusion or stenosis may cause unilateral boundary zone infarction, usually in the anterior and subcortical regions. This causes contralateral weakness of the leg more than the arm, with sparing of the face. 

Even with selective catheter angiography, there can be difficulty in distinguishing occlusion from extreme internal carotid artery stenosis, and then late views are needed to see contrast eventually passing up into the head. Moreover, because of the localized and non-concentric nature of atherosclerotic plaques, biplanar, and preferably triplanar (Jeans et al. 1986 Cuffe and Rothwell 2006), views of the carotid bifurcation are required to measure the degree of carotid stenosis accurately that is, to visualize the residual lumen without overlap of other vessels, to measure at the narrowest point and to compare with a suitable denominator to derive the percentage diameter stenosis. 

Lack of reliability in distinguishing very severe stenosis (>90%) from occlusion, and resultant uncertainty in decision making about surgery Only moderate-to-good sensitivity and specificity for severe internal carotid artery stenosis... 

Droste DW, Jurgens R, Nabavi DGC et al. (1999). Echocontrast-enhanced ultrasound of extracranial internal carotid artery high-grade stenosis and occlusion. Stroke 30 2302-2306... 

Asymptomatic Carotid Atherosclerosis Study Group (1995). Carotid endarterectomy for patients with asymptomatic internal carotid artery stenosis. Journal of the American Medical Association 273 1421-1428 Barnett HJ, Taylor DW, Ehasziw M etal. (1998). The final results of the NASCET trial. New England Journal of Medicine 339 1415-1425 Cardiac Arrhythmia Suppression Trial (CAST) Investigators (1989). Preliminary report effect of encainide and flecainide on mortality in a randomised trial of arrhythmia suppression after myocardial infarction. New England Journal of Medicine 321 406-412 Charleson ME, Horwitz RI (1984). Applying results of randomised trials to clinical practice impact of losses before randomisation. British Medical Journal 289 1281-1284... 

Moyamoya syndrome (Ch. 6) causes gradual stenosis or occlusion of the terminal portions of the internal carotid arteries or middle cerebral arteries. This leads to formation of an abnormal collateral network of fragile vessels, which occasionally rupture. It has been proposed that constructing a bypass to relieve the pressure on the collaterals would be beneficial, for example between the superficial temporal artery and the middle cerebral... 

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. 

Schroeder T (1988). Hemodynamic significance of internal carotid artery disease. Acta Neurologica Scandinavica 77 353-372 Schroeder T, Sillesen H, Sorensen O et al. (1987). Cerebral hyperfusion following carotid endarterectomy. Journal of Neurosurgery 66 824-829 Shaw DA, Venables GS, Cartlidge NEF et al. (1984). Carotid endarterectomy in patients with transient cerebral ischaemia. Journal of Neurological Sciences 64 45-53 Silvestrini M, Vernieri F, Pasqualetti P et al. (2000). Impaired cerebral vasoreactivity and risk of stroke in patients with asymptomatic carotid artery stenosis. 

Innominate or proximal common carotid artery stenosis or occlusion is quite often seen on angiograms in symptomatic patients but, unless very severe, does not influence the decision about endarterectomy for any internal carotid artery stenosis. Although it is possible to bypass such lesions, it is highly doubtful whether this reduces the risk of stroke unless, perhaps, several major neck vessels are involved and the patient has low-flow cerebral or ocular symptoms. This very rare situation can be caused by atheroma, Takayasu s disease or aortic dissection. Clearly, close consultation between physicians and vascular surgeons is needed to sort out, on an individual patient basis, what to do for the best. 

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