Carotid Artery Stenosis after Radiation Therapy in a Patient with Lung Cancer: A Case Report and Literature Review

We reported a case of carotid artery stenosis with stroke symptoms detected in a patient with lung cancer after radiotherapy. The patient was a 58-year-old male with a complaint of \"a single episode of temporary amaurosis in the right eye for 10 minutes". The clinical diagnosis at admission, after consideration of the patient's age, medical history, and auxiliary examination results, was as follows: lung cancer; right common carotid artery stenosis; left common carotid artery stenosis; left vertebral artery stenosis; and right subclavian artery occlusion with right subclavian steal syndrome (Grade 3). Carotid angioplasty and stenting (CAS) were subsequently performed. During the 6-month follow-up, we observed no episode of temporary vision loss or other signs of stroke. Clinicians should pay great attention to delayed radiation-induced carotid stenosis. It is recommended that patients with a history of radiotherapy should undergo regular color Doppler ultrasound examination of the cervical region to diagnose, prevent, and treat RICS in an expedient fashion. This approach should improve survival rate and quality of life.

Diffusion-weighted Whole-body Imaging with Background Body Signal Suppression (DWIBS) as a Novel Imaging Modality for Disease Activity Assessment in Takayasu's Arteritis

A 26-year-old woman with Takayasu's arteritis (TAK) experienced back and neck pain during tocilizumab (TCZ) treatment. The levels of C-reactive protein were normal, and ultrasonography revealed no significant changes. Diffusion-weighted whole-body imaging with background body signal suppression (DWIBS) showed signal enhancement in the walls of several arteries. Contrast computed tomography showed arterial inflammation in the same lesion. After increasing the dose of prednisolone and TCZ, all signal enhancements decreased and continued to decrease, as observed on days 76 and 132. Thus, DWIBS may be a novel imaging modality for assessing the disease activity of TAK, particularly during follow-up.

A review of subclavian steal syndrome with clinical correlation

Subclavian 'steal' phenomenon is a function of the proximal subclavian artery (SA) steno-occlusive disease, with subsequent retrograde blood flow in the ipsilateral vertebral artery (VA). The symptoms from the compromised vertebrobasilar and brachial blood flows constitute the subclavian steal syndrome (SSS), and include paroxysmal vertigo, drop attacks and/or arm claudication. Once thought to be rare, the emergence of new imaging techniques has drastically improved its diagnosis and prevalence. The syndrome, however, remains characteristically asymptomatic and solely poses no serious danger to the brain. Recent studies have shown a linear correlation between increasing arm blood pressure difference with the occurrence of symptoms. Atherosclerosis of the SA remains the most common cause. Doppler ultrasound is a useful screening tool, but the diagnosis must be confirmed by CT or MR angiography. Conservative treatment is the initial best therapy for this syndrome, with surgery reserved for refractory symptomatic cases. Percutaneous angioplasty and stenting, rather than bypass grafts of the subclavian artery, is the widely favored surgical approach. Nevertheless, large, prospective, randomized, controlled trials are needed to compare the long-term patency rates between the endovascular and open surgical techniques.

[Comparative analysis of carotid-subclavian transposition and stenting in case of stenotic damage of subclavian artery]

So carotid-subclavian transposition and stenting are effective and safe methods of correction of occlusive subclavian artery disease. Angioplasty and stenting of the subclavian artery is particularly indicated in patients with high surgical risk. Patients at low risk of surgery is preferred execution carotid-subclavian transposition.

Long-term results of endovascular therapy for proximal subclavian arterial obstructive lesions

BACKGROUND

Endovascular therapy is a treatment option for localized occlusion of the subclavian artery. In this report the long-term experience with 59 patients is presented.

METHODS

Between June 1998 and September 2008, we used endovascular therapy to treat 61 subclavian arterial obstructive lesions in 59 patients (46 males and 13 females, 34 - 82 years of age with a mean age (61.9 + or - 11.0) years). Twenty patients (34%) had clinical symptoms due to vertebrobasilar insufficiency, 26 (44%) had disabling arm ischemia, and 13 (22%) had both symptoms. We performed all procedures under local anesthesia. The approaches were from the femoral artery (n = 47), brachial artery (n = 1, involving bilateral subclavian disease) or both (n = 11). Sixty stents were implanted. All patients were followed-up at 1, 3, 6, and 12 months post-procedure, and annually thereafter.

RESULTS

We achieved technical success in 58 (95.1%) arteries, all of which were stented. There were three technical failures; two were due to the inability to cross over an occlusion, necessitating the switch to an axillo-axillary bypass, and the third was due to shock after digital subtraction angiography and prior to stenting. Arterial stenosis pre- and post-stenting was (83.6 + or - 10.8)% and (2.5 + or - 12.5)% (P < 0.01). Clinical success was achieved in 55 of the 59 patients (93.4%). Of the four clinical failures, three were technical and the remaining patient had a stent thrombosis. Systolic blood pressure difference between the two brachial arteries was (44.7 + or - 18.5) vs. (2.2 + or - 3.9) mmHg (P < 0.01). Primary patency was 98% at 12 months, 93% at 24 months, and 82% at 5 years. Five patients were lost to follow-up by 12 months post-stenting. Significant recurrent obstruction developed in five patients with resumption of clinical symptoms. The overall survival rate was 98.2% at 12 months, 89.5% at 24 months, and 84.5% at 5 years.

CONCLUSIONS

Endovascular therapy for proximal subclavian arterial obstructive lesions is effective and successful. This minimally invasive treatment may be the first choice of treatment for proximal subclavical arterial obstructive lesions.

[Supra-aortic trunks occlusive disease: three different treatment approaches]

Unlike carotid bifurcation atherosclerotic stenosis, supra-aortic trunks (SAT) occlusive disease is rare and its revascularization uncommon, accouting for less than 10% of the operations performed on the extracranial brain-irrigating arteries. There are three different treatment approaches: transthoracic, extra-anatomic cervical and endovascular. Endovascular repair is gaining popularity as first-line therapy for proximal lesions with favorable anatomy because of its low morbidity and rare mortality. Extra-anatomic bypass is a safe and durable reconstruction and should be considered in patients with single vessel disease, with cardiopulmonary high-risk or with limited life expectancy. If cardiac surgery is needed, central transthoracic reconstruction is preferable, and the two procedures should be combined. The long-term patency of bypasses with aortic origin, specially when multiple vessels are involved, is superior to other repair techniques. We present three clinical cases that illustrate each of these therapeutic strategies: central brachiocephalic revascularization and synchronous cardiac surgery in a patient with complex SAT atherosclerosis disease; subclavian-carotid transposition for disabling upper limb claudication; and subclavian artery stenting for subclavian-steal syndrome. Surgical approach selection should be based on the individual patient's anatomy and operative risk.

Coronary-subclavian steal syndrome presenting with ventricular tachycardia

Coronary-subclavian steal through the left internal mammary graft is a rare cause of myocardial ischemia in patients who have had a coronary bypass surgery. We report a 70-year-old man who presented with sustained monomorphic ventricular tachycardia 5 years after the surgical creation of a left internal mammary to the left anterior descending artery. Cardiac catheterization illustrated that the left subclavian artery was occluded proximally and that the distal course was visualized by retrograde filling through the left internal mammary graft. Clinical ventricular tachycardia was reproducibly induced with a single ventricular extrastimulus, and antitachycardia pacing terminated the tachycardia. Restoration of blood flow by way of a Dacron graft placed between the descending aorta and the subclavian artery resulted in the total relief of symptoms. Ventricular tachycardia could not be induced during the control electrophysiologic study after surgical revascularization.

Unusual etiology of upper extremity ischemia in a scleroderma patient: thoracic outlet syndrome with arterial embolization

Although the causes of digital ischemia and necrosis are diverse in women, the most common etiology is connective tissue disease. We describe a patient with scleroderma who presented with arm ischemia secondary to arterial embolization from thoracic outlet syndrome. Her sublavian artery was compressed by the anterior scalene muscle and a cervical rib, leading to a stenosis with poststenotic dilation of the artery. Within the aneurysmal formation was a thrombus, which was probably the source of the distal embolization. The patient underwent surgical resection of the cervical and first rib. The abnormal portion of the subclavian artery was resected and replaced with an interposition graft.

A Case Report of Coronary Subclavian Steal Syndrome in a Young Woman

A 41-year-old woman presented with complaints of increasing angina pectoris and coldness of her left arm for 1 month. Six months ago, she had undergone triple coronary artery bypass grafting (CABG) including left internal mammary artery (LIMA) to left anterior descending artery (LAD) and two saphenous vein grafts to the diagonal branch of LAD and obtuse marginal branch of the circumflex artery. Coronary angiography revealed that contrast media injected into the saphenous vein graft coursing down the diagonal branch flowed up to LAD and drained into the LIMA opacifying the left subclavian artery. Arch angiography documented a total occlusion of the left subclavian artery. A polytetrafluoroethylene graft was anastomosed between the left common carotid and axillary artery. After operation, the symptoms disappeared and blood pressure in her left arm recovered. This complication could be prevented by identification of subclavian artery stenosis during coronary angiogram or CABG. This study may suggest that subclavian artery angiography should be performed in patients who will undergo CABG even for a young woman such as our case.

Diagnosis and Management of Subclavian Artery Stenosis Prior to Coronary Artery Bypass Grafting in the Current Era

There are several approaches to managing subclavian artery stenosis (SAS) prior to coronary artery bypass grafting (CABG) with an intended internal thoracic artery (ITA) graft to the left anterior descending (LAD) artery. We herein review the incidence of and various diagnostic modalities for detecting SAS. Published relevant clinical studies from the interventional cardiovascular and cardiac surgical literature are summarized. Particular emphasis is placed on the efficacy of various approaches to the patient diagnosed with SAS prior to CABG. Stenting the subclavian artery prior to bypass surgery and using an in situ ITA is compared to using the ITA as a "free" graft. The incidence of restenosis after subclavian artery angioplasty or stenting is not trivial and has been reported to occur at a rate of 6% to 21%; however, the average rate of restenosis with stenting appears to be in the mid-teens. Subacute subclavian stent thrombosis or occlusion is exceptionally rare, suggesting that a percutaneous approach to SAS is reasonable prior to CABG. For patients requiring emergent revascularization, placement of a free ITA graft to the LAD appears to be a safe and durable treatment as patency rates are comparable to that of an in situ LITA to the LAD. In summary, although no randomized clinical trials address the optimal management of SAS prior to CABG, both percutaneous and surgical options appear to be safe and reasonably durable.

Subclavian Artery Dissection and Triple Infarction of the Nervous System

BACKGROUND

Subclavian artery dissection is a rare entity. It is usually associated with anomalous aortic vasculature. Only with trauma or catheterization procedures is subclavian artery dissection with normal aortic vasculature reported.

PATIENT

We describe a patient with intrascapular pain, an occipital headache, and 3 distinct infarctions in the nervous system. He had spontaneous subclavian artery dissection with normal aortic vasculature.

CONCLUSION

Subclavian artery dissections should be suspected in patients with intrascapular pain, occipital or cervical pain, and symptoms within the posterior circulation.

Subclavian steal syndrome with an unusual presentation

Steal syndrome has been known since 1960 in the medical literature. It is the pathological process in which blood flows in reverse direction and if vessels supplying the intracranial structures are involved, a variety of neurological symptoms may develop. In this paper, we report a case with left subclavian steal syndrome that presented solely by paroxysmal numbness on the right side of the lip and tongue and discuss the clinical importance from the neurological point of view.

Imaging diagnosis of subclavian steal syndrome secondary to takayasu arteritis affecting a left-side subclavian artery

Takayasu arteritis (TA) is a rare form of large-vessel, chronic, occlusive vasculitis. It involves mainly aorta and its main branches, causing stenosis and/or obstruction. Its frequency has been estimated at 2.9 cases per 1 million people. Epidemiologically, it is found principally in young female patients and is more prevalent in Asia and Latin America. When there is severe stenosis or occlusion in subclavian artery, the phenomenon of subclavian steal syndrome (SSS) occurs, which usually causes symptoms of the vertebrobasilar territory because blood supply to the arm is sustained by reversal of flow in ipsilateral vertebral artery. We describe a case of SSS thought to be due to TA in a Mexican woman. Doppler ultrasound of neck vessels showed retrograde flow in left vertebral artery during systole. Digital subtraction angiography confirmed 30% stenosis of left subclavian artery with filling of left vertebral artery in retrograde direction. In presenting this case, we carried out a brief review of TA, main features in imaging diagnosis of SSS, and the infrequently reported association of TA with SSS.

Duplex Doppler ultrasonography of subclavian steal syndrome--three case reports

Three cases of subclavian steal syndrome were detected by duplex Doppler ultrasonography. Ultrasonography demonstrated retrograde flow with to-and-fro pattern in the right vertebral artery in two cases, and reflux with diastolic flow deceleration in one case. Interventional treatment with stenting was successfully performed in two cases and conservative treatment was given in one case. Ultrasonography is an effective noninvasive method for the evaluation of the vertebral artery, and should become a routine part of cerebrovascular examinations.

Hemiballism with insular infarction as first manifestation of Takayasu's arteritis in association with chronic hepatitis B

BACKGROUND

Takayasu's arteritis is a chronic inflammatory idiopathic disease involving large arteries like the aorta and its primary branches. Cell-mediated autoimmunity leading to vascular injury has been suspected in its pathogenesis although the antigen inducing the process remains unknown.

CASE REPORT

A 50-year-old male patient suffered from acute hemiballism. Neuroimaging showed an infarction of right temporal insular cortex. Neurosonology and MR-Angiography revealed bilateral long-distant subtotal stenosis of the common carotid artery and left-sided occlusion of the subclavian artery. Positive hepatitis B serology with active viral replication was found. In the absence of other vasculitis or inflammation markers, Takayasu's arteritis was diagnosed and steroid therapy was started.

CONCLUSIONS

Unilateral insular lesions may lead to transient hemiballistic movements which could be the result of decreased inhibitory output of the insula to basal ganglia. The hepatitis B virus possibly contains a surface antigen inducing a specific cellular immune response leading to Takayasu's arteritis.

Right aortic arch with isolated left brachiocephalic artery

Right aortic arch with complete isolation of the left brachiocephalic artery is an extremely uncommon anomaly of the aortic arch. This case reports the hitherto unreported association of the right aortic arch with isolated left brachiocephalic artery presenting with a subclavian steal syndrome detected in a 36-year-old female patient being investigated for increasing attacks of episodic dizziness, vertigo, and left upper limb claudication spanning 1 year. A review of the literature relevant to this condition is presented. It is likely that with advances in imaging techniques and a wider clinical usage of these investigative modalities there will be further recognition of these uncommon conditions.

Bilateral subclavian steal syndrome through different paths and from different sites--a case report

Cases of cerebro-subclavian steal syndrome have been reported in the medical literature since 1960. This most often occurs on the left side because of the higher rate of involvement of the left subclavian artery in comparison to the other brachiocephalic branches of the aortic arch. With the use of the internal mammory artery as a conduit for coronary artery bypass, in the past three decades increasing numbers of coronary-subclavian steal in addition to the cerebro-subclavian steal have been observed. The authors report a case of bilateral subclavian steal syndrome through both vertebral arteries, the right common carotid artery, and the left internal mammory artery, without significant signs and symptoms of cerebral ischemia or anginal pain.

[Doppler ultrasound of precerebral arteries. A retrospective study of referral routines and findings]

This study reports the activities of the cerebrovascular laboratory at Ullevål hospital in 1990. 713 patients (332 men and 381 women; mean age 60 years) were examined with pulsed Doppler ultrasound. Pathological findings were detected in 202 patients (28%). Among these, 43 patients (6%) had stenosis in the internal carotid artery < 70%, 31 patients (4.3%) stenosis > or = 70% and 30 patients (4.2%) had occluded internal carotid artery. 48 patients (6.7%) had stenosis of the external carotid artery. Subclavian steal was detected in 16 patients (2.2%), stenosis in the subclavian artery without steal in 12 patients (1.7%), and atypical or suspect pathological signals from the vertebral artery in 22 patients (3.1%). The occurrence of pathological ultrasound findings was strongly related to the reasons for referral. There were pathological ultrasound findings in 77% of the cases with symptomatic neck bruit. No pathological findings were detected in patients < 50 years who were referred for ultrasound examination because of vertigo. Most patients were referred by the Department of Neurology (n = 386), but relatively few patients (16%) had pathological ultrasound findings. The occurrence of pathological findings in patients referred from other hospital departments (n = 131) and general practitioners (n = 84) was 53% and 44%, respectively.

Subclavian steal syndrome. A review of 59 consecutive cases

Subclavian steal syndrome results from reversal of flow through the vertebral artery from occlusion or stenosis of the proximal subclavian or brachiocephalic artery. The resulting "steal" phenomenon leads to the common symptoms of vertigo, syncope, and intermittent claudication of the involved upper extremity. However, these symptoms rarely, if ever, result in permanent neurological damage in and of themselves. A significant percentage of patients will have concomitant extracranial atherosclerotic disease present. Visual disturbances and transient paralysis occur more often in patients with coexistent carotid disease. Carotid artery endarterectomy should be performed first in these patients and will likely resolve all symptoms. Carotid subclavian by-pass using a PTFE graft conduit remains the procedure of choice for patients suffering from disabling symptoms and can be performed with low operative risk and morbidity with excellent long term results.

Anomalous origin of the brachiocephalic vessels with right aortic arch and contralateral subclavian steal syndrome

Anomalies of origin of the brachiocephalic vessels are uncommon. The authors report a new case of such an abnormality revealed by a subclavian steal syndrome. The angiographic study showed a right aortic arch with hypoplasia of the origin of the left subclavian a., which arose from the descending aorta, and a collateral cervical circulation derived from the left vertebral a. and the right subclavian a.

Asymptomatic subclavian steal syndrome in children following cardiac surgery: a potential hazard with re-operation?

We describe a case of fatal hypoxic-ischemic encephalopathy, leading to brain death following the modified Fontan procedure in a child with asymptomatic subclavian steal syndrome (SSS). This patient's brain death was most likely multifactorial in view of his postoperative course. However, we believe that the presence of the SSS contributed to the abnormal cerebral circulation during surgery and postoperatively, leading to brain death. The presence of SSS in patients undergoing an open-heart procedure may be a risk factor for cerebral ischemia or brain death.

Right aortic arch with isolation of the left subclavian artery: case report and review of the literature

Of the right aortic arch anomalies, a right arch with isolation of the left subclavian artery is the least common. Herein we describe a 52-year-old woman in whom this anomaly was discovered during cerebral angiography for evaluation of a giant symptomatic intracavernous carotid aneurysm. Isolation of the left subclavian artery may be suggested in a patient with a right arch in whom the blood pressure or pulse in the left upper extremity is diminished. Although the isolated left subclavian artery produces the hemodynamic alterations of a subclavian steal, review of the 39 cases reported in the literature revealed only 5 patients with symptoms suggestive of vertebrobasilar insufficiency and 5 patients with weakness of the left upper extremity. Although the patient we describe had no known heart disease, congenital heart disease was present in 23 of the 39 reported cases (59%), tetralogy of Fallot occurring most frequently.

A case of subclavian steal syndrome with a specific form of obstruction of the right proximal subclavian artery

We experienced a case of subclavian steal syndrome (SSS) with a specific form of obstruction of the right proximal subclavian artery. The patient was a 44-year-old man who complained of numbness of the right hand. Right carotid-subclavian artery anastomosis was performed under general anesthesia. The obstructed segment was a fibrous cord, 3.5 cm in length and 2.0 mm in diameter. Postoperatively, the patient was free from the symptom. In the Japanese literature, 73 cases of SSS were reported from 1965 to 1986, and the etiology was mentioned in 64 cases. In 28 cases the cause was aortitis syndrome (43.8%), in 22 cases arteriosclerosis (34.4%), in 13 cases congenital malformation (20.3%), and in 1 case iatrogenic lesion (1.6%). These data indicated that SSS caused by congenital malformation was not so rare as previously believed. Of 13 cases with congenital malformation, our case and 3 other cases had similar aspect in clinical features. All 4 patients were middle-aged men (aged 34, 26, 45 and 44 years) with a fibrous cord at the proximal portion of the right subclavian artery. None had any other cardiovascular anomalies.

Stenosis and occlusion of the subclavian artery: ultrasonographic and clinical findings

Continuous-wave (CW) Doppler sonography has proved to be a reliable tool both to detect subclavian stenosis or occlusion and to detect reversal of blood flow in the vertebral artery. This method is entirely atraumatic and in contrast to angiography allows investigation of asymptomatic patients and provides more representative data for epidemiological studies. The incidence of subclavian stenosis or occlusion was 1.15% among the 23,500 patients examined in our department between 1978 and 1985. Of the 272 patients with unilateral or bilateral subclavian stenosis or occlusion, 54% were asymptomatic with no subjective complaints and were normal upon neurological examination; 29% reported vertebrobasilar transient ischaemic attacks (TIAs), with or without concomitant TIAs or infarction in the vascular territory of the carotid arteries; and 17% complained of symptoms exclusively referring to the region of carotid blood supply. Reversal of blood flow in the ipsilateral vertebral artery was detected in 152 patients (56%). The incidence of neurological symptoms within this group was double that found in patients without steal. None of the patients suffered from permanent vertebrobasilar damage. In most cases, subclavian artery disease was due to atherosclerosis. For 13 patients an inflammatory, iatrogenic, traumatic, or congenital aetiology could be assumed. The marked preponderance of left-sided subclavian stenosis or occlusion, reported by others, could be confirmed among our patients, but was less pronounced for tight stenoses than for occlusions. Mild-to-moderate subclavian stenoses were about equally distributed on each side.

What determines the symptoms associated with subclavian artery occlusive disease?

Symptoms associated with subclavian artery stenosis are related to reduced cerebral or arm blood flow. A large difference in blood pressure between the two arms is associated with symptoms of arm ischemia alone and is usually caused by an anatomic variant. The presence or absence of a radiologic steal alone did not seem to determine the type or presence of symptoms. The type of cerebral symptoms seems to be determined by the location of other extracranial vascular stenosis. In patients with hemispheric symptoms there was a higher incidence of anterior circulation insufficiency and a greater reduction in the overall cerebral blood flow. In patients with nonhemispheric symptoms a higher incidence of posterior circulation insufficiency occurred. There may be a small group with nonhemispheric symptoms and a subclavian artery stenosis in whom reversed vertebral artery blood flow is the sole determinant. Perhaps more accurate delineation of other extracranial vascular stenosis would help determine what stenosis in addition to the subclavian artery occlusive disease determines the presenting symptoms. Surgical repair of these lesions may lead to an improved cure rate in this group of patients.

Interruption of the aortic arch in an infant with left subclavian steal syndrome. Case report

An unusual case of interruption of the aortic arch with flow to the descending aorta through the left vertebral and left subclavian arteries is described. The ductus arteriosus was functionally closed. The aortic arch was reconstructed with a PTFE graft, but the patient died because of lung problems, related to a high left-to-right shunt through a ventricular septal defect. A new surgical approach is postulated in view of the unusual hemodynamic features. Surgical control of pulmonary congestion could be the initial step, followed by aortic arch reconstruction later when insertion of a non-restrictive aortic prosthesis is possible.

Vertebrobasilar ischemia after total repair of tetralogy of Fallot: significance of subclavian steal created by Blalock-Taussig anastomosis. Vertebrobasilar ischemia after correction of tetralogy of Fallot

Patients who have undergone a Blalock-Taussig anastomosis for treatment of congenital heart disease may have the vascular anatomy of the subclavian steal syndrome. Cerebral ischemia has been reported in such patients, but not when total surgical correction has eliminated other predisposing factors. We report a patient who developed vertebrobasilar insufficiency 31 years after Blalock-Taussig anastomosis and 4 years after total intracardiac repair of tetralogy of Fallot. He had angiographically proven subclavian steal and no other known predisposing factor for cerebral ischemia. This case suggests that symptomatic subclavian steal may be a late risk of surgical treatment of congenital heart disease that leaves the vascular anatomy of subclavian steal intact. Vascular reconstructive surgery can be effective treatment for these patients and may be indicated prophylactically at the time of intracardiac repair if subclavian steal syndrome becomes a more frequently recognized sequela of prior Blalock-Taussig anastomosis.

Progressive supranuclear palsy in the course of subclavian steal syndrome

A 70-year-old man manifested during four years a progressive clinical picture consisting in palsy of gaze, axial rigidity, disorders of standing and gait, dysarthria, dysphagia. Neuroradiological investigations demonstrated proximal thrombosis of the left subclavian artery with subclavian steal. At necropsy, degenerative changes in several areas of the basal ganglia and brain stem, with presence of globose neurofibrillary tangles, were found, consistently with the pathologic pattern of the Progressive Supranuclear Palsy (PSP). The association of PSP and subclavian steal syndrome has not been previously reported, to our knowledge. We hypothesize that chronic ischemia, due to subclavian steal syndrome, in the vertebral basilar system and its watershed versus carotid system may have favoured the appearance, in these same areas, of the changes of the PSP.

Segmental intervertebral anastomosis in subclavian steal

Segmental intervertebral arterial connections originate from normal vascular channels which are commonly seen on selective vertebral arteriography. In subclavian steal, these vessels can hypertrophy and form important collateral pathways. The significance of their haemodynamic contributions may be assessed by their multiplicity and calibre. Lateral or oblique projections in addition to frontal visualization may be required to differentiate the various transcervical channels which lie either anterior or posterior to the vertebral bodies.