Magnetic resonance angiography of collateral compensation in asymptomatic and symptomatic internal carotid artery stenosis

OBJECTIVE: In patients with stenosis of the internal carotid artery (ICA), the presence of collateral circulatory pathways may be crucial to maintain cerebral perfusion pressure, metabolism, and function. The purpose of the present study was to determine whether patients with asymptomatic stenosis of the ICA have a better collateral ability of the circle of Willis when compared with patients with symptomatic ICA stenosis. METHOD: Magnetic resonance angiography consisting of the circle of Willis was performed in 19 patients with severe asymptomatic ICA stenosis and in 21 patients with severe symptomatic ICA stenosis prior to carotid endarterectomy and in 53 control subjects. Between group comparisons were made for function (directional flow) and anatomy (diameter). RESULTS: In patients with asymptomatic ICA stenosis, the prevalence of collateral flow via the anterior communicating artery was significantly increased (37%, 7 of 19) compared with symptomatic patients (10%, 2 of 21) and control subjects (0%; P <.001). Patients with asymptomatic ICA stenosis demonstrated the largest mean diameter of the anterior communicating artery (1.33 +/- 0.18 mm) compared with patients with symptomatic ICA stenosis (1.22 +/- 0.18 mm) and control subjects (1.06 +/- 0.10 mm, P <.05). No differences in collateral flow pattern or diameter were found for the posterior communicating artery between the groups. CONCLUSIONS: The present cross-sectional study demonstrates the importance of an adequate hemodynamic compensation via the circle of Willis in patients with ICA stenosis. Whether differences in collateral compensation can be used to select patients for CEA has yet to be determined.     

The use of aperiodic analysis of the EEG during carotid artery surgery

A new processed EEG machine, the Lifescan, which uses aperiodic analysis, was used to monitor cerebral activity prospectively in twenty-one patients undergoing carotid artery surgery under general anaesthesia. The machine was easy to apply, use and read. Volatile agents caused a bilateral decrease in high frequency activity. Unilateral changes consistent with cerebral ischaemia at the time of carotid cross-clamping were also seen. One such prolonged change was not associated with neurological deficit. A further patient awoke with neurological deficit without displaying Lifescan evidence of ischaemia. The machine requires further assessment.     

Noninvasive diagnosis of internal carotid artery occlusion

In summary, internal carotid artery occlusion can be reliably diagnosed by noninvasive techniques, particularly when complementary studies such as B-mode imaging, oculopneumoplethysmography and Doppler frequency spectral analysis are used in combination. Our data suggest that it may also be possible to distinguish acute thrombosis from chronic occlusion by real-time ultrasonography, although further evaluation is necessary. Additional clinically important information about the ipsilateral external carotid artery and the contralateral internal carotid artery is also obtained with this combination of noninvasive studies. Finally, although internal carotid artery occlusion remains a therapeutic challenge to the clinician, its noninvasive diagnosis may be of great help in planning early therapy and in determining arteriographic needs.     

颈动脉手术的麻醉管理与脑保护

目的：探讨颈动脉手术的麻醉管理方法与脑保护效果。方法：37例颈动脉手术的病人，在全身麻醉的基础上采用局部低温及药物治疗综合实施脑保护，对其中12例病人以监测脑氧供需平衡的方法，评价综合脑保护措施的效果。结果：全组病人麻醉及脑保护效果满意，颈动脉阻断后的颈动－静脉血氧含量差和脑氧摄取率有增加趋势（P＞0．05），但颈动脉开放后，脑的颈动－静脉血氧含量差和脑氧摄取率比阻断前显著增加（P＜0．05），结论：在全身麻醉的基础上，局部低温及药物治疗等综合措施有一定的脑保护作用。但不能完全消除脑的缺血－再灌注损伤。     

The haemodynamic value of external carotid artery collateral blood supply in carotid artery disease

In the presence of severe obstruction of the internal carotid artery (ICA) blood supply to the ipsilateral hemisphere may be provided by collaterals. Whereas the circle of Willis in many cases makes a substantial contribution to cerebral perfusion, the value of collateral blood supply originating from the external carotid artery (ECA) is not clear. In thirty-five patients undergoing carotid endarterectomy (24 with proven external carotid artery collaterals) intra-arterial blood pressures were measured across the ICA stenosis, prior to endarterectomy. In order to evaluate the haemodynamic value of ECA collaterals, the distal ICA pressure was measured with and without the ECA clamped. In addition, volume blood flow in the common carotid artery was measured with and without the ECA clamped, before and after endarterectomy. No significant change in distal ICA pressure was observed when the ECA was clamped, whether or not external carotid artery collaterals had been demonstrated preoperatively. The greatest reduction in mean distal ICA pressure observed upon ECA clamping was 8 mmHg. However, this only occurred in three of 11 patients with a severe pressure reduction across the stenosis. ICA blood flow increased significantly following endarterectomy whereas ECA flow was reduced. This study indicates that ECA collaterals in most cases do not contribute substantially to cerebral perfusion. Endarterectomy of the ECA, in order to improve cerebral circulation, seems justified only in selected cases, where the distal ICA pressure has been shown to be severely reduced.     

Preoperative assessment of clamping in carotid artery surgery and adaptation of the operative technic

A retrospective study of 150 consecutive patients undergoing revascularization of internal carotid artery for atheromatous lesion of carotid bifurcation, included analysis of collaterals being compressed by common carotid artery simulating clamping. Two exploratory procedures had been applied routinely: global suprasigmoid digital subtraction angiography and Doppler velocimetry. Two groups of patients could be defined: clamping without risk (95.4%) and clamping at risk (4.6%). For the group of clamping at risk a surgical strategy is proposed allowing clamping without shunt by bypass between subclavian and internal carotid arteries of by bypass between common and internal carotid arteries because of the external carotid artery collaterals left untouched. A shunt is only necessary when the latter artery is occluded. Results of this series of patients explored in this way and operated upon confirmed these data: no clamping accident in the 1st group, one transient ischemic accident in the 2nd.     

Advantages of continuous electroencephalographic monitoring during carotid artery surgery

One hundred carotid endarterectomies were performed using selective shunting based on continuous electroencephalographic monitoring (CEM) for the detection of cortical ischemia. Changes associated with ischemia were loss of frequency and amplitude. The results of CEM were correlated with carotid stump pressure (CSP) measurements. Only one (4%) of the 25 patients who developed an abnormal EEG had a mean CSP greater than 50 mmHg: however, CEM was positive in only 24 (45%) of the 53 patients with a CSP less than 50 mmHg. Using EEG as a standard, no CSP criterion (50 or 25 mmHg) was sufficiently sensitive and specific to recommend its routine use (50 mmHg--96% and 61% respectively; 25 mmHg--40% and 96% respectively). Operative mortality was 1%. The three intraoperative neurologic deficits (3%), one transient and two permanent, are analyzed with respect to the operative EEG findings. In the 100 endarterectomy patients and three more undergoing carotid exploration or excision of carotid body tumor EEG changes due to anesthetic problems not associated with carotid clamping were often identified. In 48 additional endarterectomies a computerized display and disk storage of six selected EEG leads, each with a reference trace for comparison, has provided information equivalent to that from the full EEG. EEG monitoring is more accurate than CSP measurement for identifying patients who require shunting, safely dispensing with a shunt in many cases which would otherwise be shunted by standard CSP criteria.(ABSTRACT TRUNCATED AT 250 WORDS)     

History of carotid artery surgery

The history of carotid artery surgery is briefly reviewed. The introduction of cerebral angiography, coupled with increasing awareness of the extracranial location of offending lesions responsible for stroke syndromes, has resulted in the use of carotid endarterectomy as an important clinical therapeutic modality.     

Noninvasive differentiation of carotid artery occlusion from high-grade stenosis

The differentiation of high-grade carotid artery stenosis from occlusion can be a difficult but important diagnostic dilemma. The authors used a combination of duplex scanning, pulsed spectrum analysis, audible analysis of continuous wave doppler signal, and peri-orbital doppler compressions to accurately differentiate high-grade stenosis from occlusion in a series of 24 patients.     

Internal carotid artery stenosis and external carotid artery occlusion with unusual extracranial collateral pathway: case report

A patient with stenosis of the internal carotid artery and occlusion of the external carotid artery associated with an unusual extracranial collateral pathway is presented. A 63-year-old man was hospitalized for sudden onset of black-out after urination. He was alert, and no neurological deficit was found. MRI showed multiple lacunae in the bilateral putamens. Cerebral angiogram demonstrated severe stenosis of the left internal carotid artery at its cervical segment and complete occlusion of the left external carotid artery at its origin. The ascending pharyngeal artery originated from the left internal carotid artery above its stenotic lesion and the superior thyroid artery originated from the left common carotid artery. The sternocleidomastoid branch from the left superior thyroid artery and the muscular branch from the left vertebral artery anastomosed with the muscular branch of the ascending pharyngeal artery. The ascending pharyngeal artery maintained patency of the internal carotid artery. It is important to perform vertebral angiography when there is proximal occlusion and severe stenosis of the internal carotid artery, and when the ascending pharyngeal artery has not been clearly identified as a branch from the ipsilateral external carotid artery on the common carotid angiogram.     

Simultaneous microscopic and endoscopic monitoring during surgery for internal carotid artery aneurysms

OBJECT: The authors of this study evaluated the efficacy of simultaneous microscopic and endoscopic monitoring during surgery for internal carotid artery (ICA) aneurysms. METHODS: The endoscopic technique was applied during microsurgery in 11 patients with 13 aneurysms. Nine of these lesions were located on the posterior communicating artery (PCoA), three in the paraclinoid region, and one on the anterior choroidal artery (AChA). Eight patients had unruptured aneurysms and three had ruptured aneurysms. The endoscope was introduced after first exposing the aneurysm through the microscope and was gripped firmly by an airlocked holding arm fitted with a steering system throughout the entire surgery, including dissection of the perforating arteries and application of the aneurysm clips. Regarding paraclinoid aneurysms, clips were applied through direct visualization of the ophthalmic artery and the proximal neck. In a case involving a superior hypophyseal artery aneurysm in the paraclinoid segment, a ring clip was applied without removing the bone structure around the optic canal. In all aneurysms of the PCoA and the AChA, perforating arteries behind the lesion were identified and dissected using endoscopic control. The aneurysm clip was applied in the best position in a single attempt in 10 of 11 patients. There was no surgical complication related to the endoscopic procedures. CONCLUSIONS: Simultaneous monitoring with the microscope and endoscope is extremely useful in applying clips to ICA aneurysms. This combined method allows for direct dissection of the aneurysm, perforating vessels, and the main trunk in an area not visible through the microscope's eyepiece and promises better surgical results.     

Somatosensory-evoked potentials during carotid artery surgery: experience in 400 operations

A prospective study was undertaken to determine the efficacy of monitoring somatosensory-evoked potentials (SEP) during carotid artery surgery in predicting a new ischemic neurologic deficit. Three hundred seventy-six patients underwent 400 reconstructions of the internal carotid artery. The mortality rate of the entire series was 0.8%. In 383 procedures, SEP amplitudes were always present during cross-clamping of the internal carotid artery. In spite of that, three neurologic deficits occurred, but all were associated with technical failures and not related to clamping ischemia. Complete loss of SEP amplitudes was noted in 17 procedures. Five of seven patients without an indwelling shunt showed a neurologic deficit after surgery, whereas shunt insertion in 10 resulted in three neurologic deficits. It is concluded that at present SEP recording is an accurate monitoring method in detecting clamping-related cerebral ischemia during carotid artery surgery.     

Simultaneous carotid and coronary artery surgery in asymptomatic carotid artery stenosis--report of three cases

Some patients with coronary artery disease are diagnosed as having additional carotid artery disease. This subset of patients has been identified as a high-risk group for cardiac and cerebral complications following surgical intervention. Three patients who underwent combined CEA/CABG for coexistent asymptomatic carotid occlusive disease are reported. Case 1: A 69-year-old female who suffered chest pain on exertion. Her coronary angiogram showed severe stenosis of three vessels. Her carotid angiogram showed 98% stenosis of the right internal carotid artery and poor collateral circulation. The severe stenosis of her carotid artery was considered as a risk factor for perioperative cerebral stroke. Intraoperatively, CEA preceded the CABG. Postoperative course was uneventful. Case 2: A 64-year-old male. Intermittent claudication was his initial symptom. His coronary angiogram showed stenosis in three vessels and carotid angiogram showed 75% stenosis in the right carotid artery. Simultaneous CABG and CEA was performed. His postoperative course was uneventful. Case 3: A 62-year-old male whose ECG indicated ischemic heart disease, although he had no symptoms. His coronary angiogram showed stenosis in three vessels, and 80% stenosis of his right carotid artery was observed by carotid angiogram. He underwent simultaneous surgery, and had an uneventful postoperative course. It has been reported that 1.5-8.7% of CABG patients have severe carotid artery stenosis, and perioperative cerebral stroke occurs in 0.9-16%. Simultaneous surgery was successful in our three patients who had asymptomatic carotid artery stenosis. Using this surgical approach for critical coexistent disease may minimize the incidence of perioperative cerebrovascular complications in patients undergoing CABG.     

Continuous conjunctival oxygen tension (Pcjo2) monitoring for assessment of cerebral oxygenation and metabolism during carotid artery surgery

The clinical value of noninvasive continuous monitoring of conjunctival oxygen tension for assessment of cerebral perfusion during carotid endarterectomy performed under general anaesthesia has been evaluated. The patients (n = 17; mean age 62.5 +/- 1.7 years) were monitored as follows: conjunctival oxygen tension (PcjO2); internal jugular venous oxygen tension at the skull base level (PcijvO2); arterial blood pressure; arterial and internal jugular venous blood gases; acid-base data and lactate, pyruvate levels; end-tidal CO2 concentration. The mean preanaesthetic PcjO2 level of 4.86 +/- 0.40 kPa was significantly lower than PaO2(PcjO2)/PaO2 ratio of 0.48). Following anaesthesia, a larger PcjO2-PaO2 gradient (ratio 0.32) was seen in spite of the hyperoxic situation (FiO2 = 0.40) due to vasoconstriction induced by slight hypocapnia (reduction of PaCO2 from 5.13 +/- 0.08 to 4.64 +/- 0.10 kPa). The carotid artery crossclamping resulted in a rapid and pronounced decrease of PcjO2, while PcijvO2 remained unchanged. No relationship between PcjO2 and stump pressure was found, while a significant correlation (P less than 0.02) between PcjO2 and lactate in effluent venous blood from the brain was demonstrable. It is concluded that PcjO2 monitoring seems a clinically useful trend indicator of cerebral perfusion in the individual patient. Due to large interindividual variations in basal PcjO2 readings and in PcjO2 changes during carotid artery clamping, however, transconjunctival oxygen tension monitoring does not seem to allow early and accurate recognition of impending cerebral ischaemia during carotid endarterectomy, and its routine use therefore seems of limited value.     

Management of inadvertent injury to the carotid artery during head and neck surgery

Rare, inadvertent injury to the carotid artery during head and neck surgery may result in disastrous neurologic sequelae or even death. Several cases are presented and used as the stimulus for an analytical discussion of the pathogenesis and management of cerebrovascular complications following head and neck surgery. The major pathogenetic mechanisms are identified as (1) microembolism from an ulcerated plaque; (2) intravascular thrombus with occlusion; (3) unintentional ligation, laceration, or transection; (4) ligation of a dominant external carotid; and (5) transient reduction in cerebrovascular perfusion pressure. Methods for identifying and evaluating the patient at risk for developing cerebrovascular complications are discussed and recommendations are made. The central question in the management of inadvertent arterial injury concerns whether to ligate the vessel or to restore blood flow. The controversies surrounding this issue are discussed in perspective through an analysis of current physiological concepts and of the collective clinical experiences of head and neck, vascular, and neurological surgeons handling extracranial cerebrovascular occlusive disease, penetrating injuries to the carotid artery, and tumor-related carotid catastrophes. Several factors are considered critical in determining appropriate management of any individual case; these include (1) whether recognition of the injury occurs intraoperatively or postoperatively; (2) the presence and severity of neurological deficits; (3) time from the injury to its recognition; (4) a quantitative assessment of collateral circulation; (5) a history of wound contamination or radiation therapy; (6) overall prognosis. These and other considerations are organized into a working framework through which the otolaryngologist and head and neck surgeon can better understand and manage the problem of inadvertent injury to the carotid artery.