411 Ipsilateral Subclavian Steal in Association with Aberrant Origin of the Left Vertebral Artery from the Aortic Arch John Holder1 Five cases are reported of left subclavian steal syndrome associated with anomalous Eugene F. Binet2 origin of the left vertebral artery from the aortic arch. In all five instances blood flow at Bernard Thompson3 the origin of the left vertebral artery was in an antegrade direction contrary to that usually reported in this condition. The distal subclavian artery was supplied via an extensive collateral network of vessels connecting the vertebral artery to the thyro­ cervical trunk. If a significant stenosis or occlusion is present within the left subc lavi an artery proximal to the origin of the left vertebral artery, the direction of the bl ood fl ow within the vertebral artery will reverse toward the parent vessel (retrograde flow). This phenomenon occurs when a negative pressure gradient of 20-40 torr exists between the vertebral-basilar artery junction and th e vertebral-subc lavian artery junction [1-3]. We describe five cases of subclavian steal confirmed by angiography where a significant stenosis or occlusion of the left subclavian artery was demonstrated in association with anomalous origin of th e left vertebral artery directly from the aortic arch. In all five cases blood flow at the origin of the left vertebral artery was in an antegrade direction contrary to that more commonly reported in the subclavian steal syndrome. Materials and Methods The five patients were all 44- 58-year-old men. Three sought medical attention for symptoms specificall y related to th e left arm . In the other two cases, th e presence of subclavi an steal was found during a workup for generali zed vascular disease. In the four cases where Doppler indices were performed , a blood pressure differential of 20 mm Hg or Received December 8, 1980 ; accepted after more was present between the two arms. All five pati ents underwent arch aortography. In revision April 29, 198 1 . four cases a high grade stenosis of the left subclavi an artery was found while in the fifth Presented at the annual meeting of the Ameri­ case the subclavian artery was occluded. The left vertebral artery arose directly from the can Roentgen Ray Society, San Francisco, CA, aortic arch in all five in stances (figs. 1 A and 2A). In all fi ve pati ents, an extensive coll ateral Marc h 1981 . network of vessels joined the vertebral artery to th e thyrocervical trunk (figs. 18 and 28). ' Department of Radiology, University of Arkan­ Contrast medium (and presumably blood) was carried vi a the coll ateral network from the sas for Medical Sciences, 4301 W. Markham, Little Rock , AK 7220 5. Address reprint requests left vertebral artery to the thyrocervical trunk and then to the subclavian artery distal to the to J. Holder. obstructing lesion. In all cases the left vertebral artery was visuali zed distal to the area of ' Department of Radiology, Veterans Adminis­ anastomoses and supplied bl ood to the basilar circulation although the caliber of the vessel tration Medical Center, Little Rock , AK 72206. diminished beyond the anastomoses. 3De'partment of Surgery, Veterans Administra­ All five patients had extensive extracranial vascular disease involving th e carotid arteries tion Medical Center, Little Rock , AK 7 2206. as well as in the subclavian artery. In four cases bypass procedures were recommended. In three instances a left carotid-left subclavian bypass shunt was accomplished without AJNR 2:411-413, September/ October 1981 01 95- 6 108 / 8 1 / 0 20 5 -0411 $00.00 incident. In the fourth case, the pati ent suffered an untoward incident during hi s left carotid © Ameri can Roentgen Ray Society endarterectomy so that his remaining surgery was deferred (table 1). 412 HOLDER ET AL. AJNR:2, September/ October 1981 A B A B Fig. 2.-Case 2, 51-year-old man with syncope and blurring of vision. A , Fig. 1.- Case 1, 44-year-old man with 3 year history of tingling, numb­ Aortic arc h study. High grade stenosis of proximal left subclavian artery ness, and weakness with exertion of left arm. A, Aortic arch injection. Total (small arrowheads). Left vertebral artery (LV) arises directly from aortic arch occlusion of left subclavian at origin (arrowheads ). Left vertebral artery (LV) (its origin is obscured by overlying left carotid artery). B, Selective left ari ses from aortic arch. B, Selective left vertebral angiogram (open arrows). vertebral angiogram (open arrows). Filling of distal subclavian artery via Filling of distal subclavian artery via extensive coll ateral network from verte­ collateral flow from vertebral artery to thyrocervical trunk (closed arrows). bral artery to thyrocervical trunk (closed arrows). unknown, involvement of the subclavian artery in patients with extracranial cerebrovascular disease is uncommon. Of Discussion 6,534 patients admitted to the joint study of cerebrovascular The most common cause of the subclavian steal syndrome insufficiency due to extracranial vascular occlusive disease is a large atherosclerotic plaque partly or totally occluding only 168 (2.5 %) fulfilled the criteria of subclavian steal the lumen of that artery [4]. Other causes include Takayasu [14]. In view of these uncommon sets of circumstances it is arteritis, cervical spondylosis, traumatic occlusion, or aorti­ not surprising that subclavian steal associated with anoma­ tis [5-7]. Congenital causes include aortic arch hypoplasia, lous origin of the left vertebral artery has not been previously coarctation, or interruption and right aortic arch anomalies, reported. Why it should have occurred in five patients seen usually with subclavian atresia [8]. Subclavian steal may at our institutions within a 2 year period is unknown. also occur following a Blalock-Taussig shunt or repair of an In these patients the rich collateral network of collateral aortic coarctation [9]. vessels between the vertebral artery and the thyrocervical In 1967 Mueller and Hinck [10] described one patient trunk provide the main pathway circumventing the subcla­ with bilateral subclavian artery obstruction occurring distal vian lesion. This is type 1 B of the cervical arterial collateral to the origin of the vertebral arteries. Both vertebral arteries network of Bosniak [15]. While additional collateral vessels suppli ed blood flow to their respective arms via extensive originating from the external carotid artery supply significant collateral vessels to the thyrocervical trunks. The authors amounts of blood to the arm, the vertebral-thyrocervical appropriately entitled this the thyrocervical steal. trunk pathway dominated in our cases. Bloch et al. [11] described one patient who required a Arch aortography will demonstrate the anomalous origin ligation of the right subclavian artery distal to the origin of of the left vertebral artery. Close inspection of the early the vertebral artery followfng a gunshot wound to the right arterial radiographs is necessary to properly evaluate the axill a. Blood was " stolen" from the right vertebral artery to altered anatomy. The origin of the left vertebral artery may supply the arm via muscular collaterals to the ascending be obscured by the cervical spine or the overlying left and deep cervical arteries. Kobinia et al. [1 2] refer to occlu­ carotid artery. Subtraction prints are helpful. In those in­ sion of the subclavian artery distal to the origin of the stances where the subclavian artery is not occluded, con­ vertebral artery as a type two subcla vian artery lesion. In trast will flow into the distal subclavian artery from two one such case blood was drained from the vertebral artery directions (fig. 1 B). to supply the homolateral arm. The patient did not have any Selective injection of the anomalous vertebral artery will neurologic symptoms presumably due to the large afferent show the extensive collateral network between the vertebral vertebral artery. artery and the thyrocervical trunk. Selective injection of the Origin of the left vertebral artery from the aortic arch is a other neck vessels should be done to exclude other foci of congenital anomaly said to occur in 2.4%-5.8% of cases cerebrovascular disease. These vessels will often provide [13]. While the exact incidence of the subclavian steal is additional collateral flow to t"'e distal subclavian artery. AJNR:2, September/ October 1981 IPSILATERAL SUBCLAVIAN STEAL 413 TABLE 1: Subclavian Steal: Summary of Cases Doppler Blood Case Age Signs and Symptoms Pressure Angiographic Findings S urgery I Outcome No. (years) (mm Hg) 44 3 year history tingling, Right, 120; left, Total occlusion left subclavian artery; left ver­ Left carotid-left sub­ numbness, and 70 tebral artery arises from aortic arch; distal clavian bypass weakness with exer­ left subclavian artery fills via collateral flow Good tion of left arm through thyrocervical trunk 2 51 8 month history of Right, 120; left 90% stenosis left subclavian artery; left verte­ No surg ery back pain, intermit­ 100 bral artery ari ses from aortic arch; distal tent claudication, left subclavian artery fills via coll ateral flow syncope, blurring of through thyrocervical Irunk vision 3 58 Intermittent left arm Right, 175; left, High grade long segment stenosis left subcla­ Left carotid end­ claudication and diz­ 105 vian artery; left vertebral artery ari ses from arterectomy; left ziness, left subcla­ aortic arch; collateral flow to distal left sub­ carotid-left sub­ vian and left carotid clavian artery via thyrocervical trunk; ulcer­