Magnetic Resonance Angiographic Localization of the Artery of Adamkiewicz for Spinal Cord Blood Supply

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1 CARDIOVASCULAR Magnetic Resonance Angiographic Localization of the Artery of Adamkiewicz for Spinal Cord Blood Supply Nobuyoshi Kawaharada, MD, PhD, Kiyofumi Morishita, MD, PhD, Hideki Hyodoh, MD, PhD, Yasuaki Fujisawa, MD, PhD, Johji Fukada, MD, PhD, Yoshikazu Hachiro, MD, PhD, Yoshihiko Kurimoto, MD, PhD, and Tomio Abe, MD, PhD Departments of Thoracic and Cardiovascular Surgery, and Radiology, Sapporo Medical University School of Medicine, Sapporo, Japan Background. The purpose of this study was to determine whether the artery of Adamkiewicz (ARM) can be detected by magnetic resonance angiography and to determine the usefulness of preoperative magnetic resonance angiography evaluation of the ARM. Methods. Between April 2000 and December 2003, 120 patients underwent magnetic resonance angiography for detection of the ARM. The morphology of the anterior spinal artery at the ARM junction, as revealed by magnetic resonance angiography, in 99 patients in whom ARM was preoperatively detected was classified into the following three types: noncontinuation of the anterior spinal artery above the ARM junction (type A), continuation of the anterior spinal artery above and below the ARM junction (type B), and noncontinuation of the anterior spinal artery below the ARM junction (type C). Results. The ARMs were detected in 99 (83%) of 120 patients, and from a total of 110 ARMs 105 (95%) originated from intercostal arteries branching from the left side and 94 (86%) originated between Th9 and Th11. Two ARMs were found in 11 (11%) of 99 patients in whom ARMs were detected. In 107 patients, who underwent magnetic resonance angiography to reveal the morphology of the anterior spinal artery at the ARM junction, the patterns of the anterior spinal artery were type A in 59 patients (55%), type B in 21 patients (20%), type C in 3 patients (3%) and not classified in 24 patients (22%). No spinal cord injury occurred in patients in whom the ARM had been preoperatively detected. Conclusions. Preoperative detection of the ARM is possible by magnetic resonance angiography and is very useful for reducing the incidence of ischemic injury of the spinal cord. (Ann Thorac Surg 2004;78:846 52) 2004 by The Society of Thoracic Surgeons Accepted for publication Feb 6, Presented at the Poster Session of the Fortieth Annual Meeting of The Society of Thoracic Surgeons, San Antonio, TX, Jan 26 28, Address reprint requests to Dr Kawaharada, Department of Thoracic and Cardiovascular Surgery, Sapporo Medical University School of Medicine, Sapporo, Japan, South 1, West 16, Chuo-ku, Sapporo , Japan; nobuyosh@sapmed.ac.jp. Postoperative paraplegia or paraparesis is a serious complication of reconstructive surgery of the thoracoabdominal or descending aorta, the major cause of which is thought to be spinal cord ischemia during and after the procedure. Due to advances in anesthetic and surgical techniques, the incidence of intractable neurologic complications has declined, but the rate of paraplegia or paraparesis is still in the range of 5% to 15% [1 4]. It is known that in the thoracolumbar region, the great anterior medullary artery (the artery of Adamkiewicz, arteria radicularis magna: ARM) is the dominant feeder of the spinal cord. One cause of paraplegia after an aortic operation is failure to reestablish spinal cord blood supply, the origins of which are not evident at the operation. It has therefore been suggested that reattachment of intercostals and lumbar arteries during replacement of a descending thoracic or thoracoabdominal aorta could minimize the occurrence of such complications. The importance of reattachment of the intercostal artery related to the ARM has been stressed in many reports [5 8]. Knowledge of the level of the intercostal artery from which the ARM originates before reconstructive aortic surgery would be useful for prevention of neurologic complications. Magnetic resonance angiography (MRA) [9 11] and multi-slice computed tomography (MSCT) [12, 13] have been reported to be useful for noninvasive ARM detection. However, it is not clear how these noninvasive imaging modalities can best be used when planning surgical repair and stent-grafting of thoracoabdominal aortic lesions to secure spinal blood flow and to prevent the occurrence of paraplegia/paraparesis. The purpose of this study was to determine whether the ARM and the discrepancy in sizes of the anterior spinal artery (ASA) above and below the junction of the ARM can be detected by MRA and to determine the usefulness of preoperative MRA evaluation of the ARM for predicting the likely outcome of surgical treatment of thoracoabdominal aortic aneurysm or descending thoracic aortic aneurysm by The Society of Thoracic Surgeons /04/$30.00 Published by Elsevier Inc doi: /j.athoracsur

2 Ann Thorac Surg KAWAHARADA ET AL 2004;78: MRA EVALUATION OF SPINAL CORD BLOOD SUPPLY Table 1. Rate of Detection of the Artery of Adamkiewicz by Magnetic Resonance Angiography in the Dissection Group and Nondissection Group Number Detection of ARM p Value a Dissection (86%) NS Nondissection (81%) Total (83%) a 2 analysis. ARM artery of Adamkiewicz; NS not significant. Material and Methods Patients Between April 2000 and December 2003, 120 patients underwent MRA for detection of the ARM. These 120 patients with thoracoabdominal aortic aneurysms or descending thoracic aortic aneurysms were all indicated for surgical treatment. However, several factors, including the severity of the aneurysm itself meant that the urgency of surgery varied among the individual patients. Some of the patients had double aneurysms and although abdominal aortic aneurysm repair was indicated, the descending thoracic aortic aneurysm was not large enough to warrant surgical treatment. The 120 patients included 84 men (70%) and 36 women (30%), the patients ages ranged from 19 to 83 years old (median, 65.6 years old). There were 3 patients (2.5%) with Marfan s syndrome. Forty-three patients (36%) had aortic dissection and 77 (64%) had nondissecting aneurysms. Eighty-seven (73%) of 120 patients had undergone operation for descending thoracic aortic aneurysm or thoracoabdominal aortic aneurysm (Table 1). Fifty-five patients (63%) had descending thoracic aortic aneurysm and 32 (37%) had thoracoabdominal aortic aneurysm. Seventy-one (82%) of 87 patients had undergone operations with reference to information obtained by preoperative detection of ARM. Moreover, between November 2000 and December 2003, 107 patients who underwent MRA to reveal the morphology of the ASA at the ARM junction were classified into the following three types: noncontinuation of the ASA above the ARM junction (type A), continuation of the ASA above and below the ARM junction (type B), and noncontinuation of the ASA below the ARM junction (type C). The study was approved by our ethics Fig 1. Frequency of vertebral level termination and laterality of 110 Adamkiewicz arteries. 847 committee, and informed consent was obtained from all study participants. Imaging Protocol and Data Processing The MRAs were performed with a 1.5-T unit (SIGNA Horizon LX Echospeed and with a SIGNA Infinity Excite [from January 2003]; GE Medical Systems, Milwaukee, WI). Since reconstruction of the radicular artery is considered necessary for aortic graft replacement in our institute, a 20-cm field of view (FOV) from above the L2 level was examined in each patient. Dynamic study was carried out by the enhanced three-dimensional fast spoiled GRASS (FSPGR) method (phased array spine coil; TR/TE/flip angle, minimum/minimum/10 to 5 degrees; NEX, 2; matrix, ; slice thickness, 1.6 mm; zero fill interpolation [slice ZIP 4 and in-plane ZIP 512]; no phase wrap; FOV, 20 cm; oblique-coronal section along the posterior line of the vertebral body). Gadolinium-diethylenetriaminopentaacetic acid (Gd-DTPA; MAGNEVIST, Schering, Berlin, Germany) was injected through the cubital vein (0.2 mmol/kg, 4 ml/s) followed by a 20-mL saline flush. A power injector (OPTISTAR MR; Mallinckrodt, St. Louis, MO) was used in all patients. After injection, dynamic studies were carried out five times. Scan times were 22 seconds for each session. After data acquisition, the images were stored as DICOM data sets and displayed on a diagnostic monitor at a 0.4-mm reconstruction pitch. The acquired data sets were transmitted to a workstation (Advantage Windows; GE Medical Systems). The maximum intensity projection (MIP) image was reconstructed in each of five phases. The resulting five MIP images were used for subtraction. The second to fifth phase images were subtracted. The first phase and resulting four subtraction images (total of five MIP) were presented in a movie format that followed the imaging time course. Criteria for Detection of the ARM Criteria for detection of the ARM on source and MIP images was as follows (1) being continuous to a clear blood vessel supply from the intercostal or lumbar artery in an early phase image; (2) identification of extension of a blood vessel from the dorsal branch of the intercostal or lumbar artery toward the surface of the anterior spinal cord in the early phase; and (3) diminishing vascular signal intensity in late phase. Surgical Procedure The patients who underwent repair of an aneurym of the descending or thoracoabdominal aorta using a partial cardiopulmonary bypass in elective surgery without profound hypothermic circulatory arrest under doublelumen endotracheal tube anesthesia were treated according to a previously reported procedure [14]. After the left thoracic cavity or left retroperitoneal space had been entered, cannulation into the right femoral artery and femoral vein was performed in all patients. For thoracoabdominal aortic aneurysm repair, a left thoracoabdominal incision was made with circumferential division of CARDIOVASCULAR

3 CARDIOVASCULAR 848 KAWAHARADA ET AL Ann Thorac Surg MRA EVALUATION OF SPINAL CORD BLOOD SUPPLY 2004;78: Table 2. Rate of Detection of the Artery of Adamkiewicz by Magnetic Resonance Angiography in the Patients Who Underwent Surgical Operations Patients and Operation Patients (n 120) [Total Patients/ARM Detected (%)] Thoracoabdominal aortic 32/25 (78%) aneurysm Graft replacement 31/25 (81%) Stent-graft insertion 1/0 (0%) Descending thoracic 55/46 (84%) aortic aneurysm Graft replacement 31/25 (81%) Stent-graft insertion 24/21 (88%) Observation for TAA (not 33/28 (85%) large enough for surgical treatment; including other surgical procedure) Total 120/99 (83%) ARM artery of Adamkiewicz; TAA thoracic aortic aneurysm. the left hemidiaphragm. The segmental arteries below the Th8 level, if patent, were reconstructed using the inclusion or exclusion button technique or by interposition 8-mm tubular grafts for reattachment of individual intercostal or lumbar arteries. The reason for reimplanting all patent arteries between Th8 and L1 is that the blood supply to the spinal cord has been reported to be provided by some arteries from Th8 through to L1 in 91% of cases and the ARM does not always originate from the larger segmental arteries [15, 16]. However, the Th8- through-l1 operative strategy has the following problems: (1) reattaching all of the arteries from Th8 to L1 prolongs the clamping time, which may cause spinal cord injury, and (2) some of the arteries that are reattached may not need to be reattached. Obviously, an accurate and reliable technique for identifying arteries that need to be reattached is needed. When the ARM existed in the region of graft replacement, only the intercostal or lumbar artery in the aneurysm that was detected as the origin of the ARM was reconstructed to the graft. When the ARM did not exist within the graft replacement region, the cross-clamping level was adjusted, and no intercostal or lumbar arteries were reconstructed. When the ARM could not be detected by MRA, conventional graft replacement (reconstruction of all patent intercostal or lumbar arteries) was Fig 2. Frequency of vertebral level termination and laterality of 114 drainage veins. performed. Visceral and renal arteries were also reimplanted by an island cuff technique or preserved in a beveled distal aortic anastomosis. During reconstruction, selective visceral and renal perfusion with 10F to 12F balloon cannulas was performed by clamping the outflow tubing to the lower extremities. In patients treated by stent-graft insertion repair, the following method was used. After general anesthesia, the right (or left) femoral artery was dissected for 20F to 22F delivery sheath placement. Under fluoroscopic control, a Z-based handmade stent-graft was deployed to attach to the proximal or distal aortic neck in order to isolate the aneurysm lumen. To secure the ARM branching radicular artery in distal aortic neck, the stent-graft was adjusted in length when it was formed. Most of the cases treated by stent-graft insertion repair were descending thoracic aortic aneurysms (Table 2). Surgical repair was performed on all aortic aneurysms cases whether ARM was detected by MRA or not. In patients with thoracoabdominal aortic aneurysm, stent-grafting with bypass procedure of celiac artery and superior mesemteric artery was performed. Statistical Analysis Data were processed using Stat View J-5.0 software (Abacus Concepts Inc, Berkeley, CA). Variables were compared using the 2 test and Fischer s exact test, Results Data on the branching levels of the ARMs are presented in Figure 1. ARMs were detected in 99 (83%) of 120 patients. All 99 patients had vessels that coursed toward the anterior spinal cord and were supplied from the intercostal artery. Only 1 ARM was detected in 88 (89%) of 99 patients, whereas 2 ARMs were detected in each of the other 11 (11%) patients. The laterality of the arteries originated from the intercostal artery on the left side in 105 (95%) of the 110 ARMs. In the 11 patients in whom 2 ARMs were detected, the ARMs originated unilaterally in 10 patients and bilaterally in 1 patient, and the ARMs were between Th9 and Th11 in 94 (85%) of 110 ARMs. In the remaining 21 patients (18%), no ARM was observed. Data on the vertebral levels of the drainage veins are illustrated in Figure 2. The drainage veins presented high signals in the third phase, and signal intensity was maintained during the following phases. Drainage veins were detected in 93 (80%) of 114 patients. A large proportion of ARMs originated from intercostal arteries branching in the left direction, but the drainage vein showed bilateral origination and revealed a tendency to have a lower vertebral level than the ARM. The morphology of the ASA at the ARM junction was determined by MRA in 83 (78%) of 107 patients. The patterns of the ASA were type A in 59 patients (55%), type B in 21 patients (20%), type C in 3 patients (3%), and not classified in 24 patients (22%) (Fig 3). Forty-three patients (36%) had aortic dissection and 77 (64%) had nondissecting aneurysms. Detection rate was

4 Ann Thorac Surg KAWAHARADA ET AL 2004;78: MRA EVALUATION OF SPINAL CORD BLOOD SUPPLY 849 patients in whom the ARM was not preoperatively detected and 71 elective thoracoabdominal or descending thoracic aortic aneurysm operations were performed in patients in whom the ARM was preoperatively detected. Table 4 lists the postoperative data for these groups. There was a significant difference in the rate of postoperative paraplegia between the two groups. CARDIOVASCULAR Fig 3. The morphology of the ASA above the ARM junction was classified. Type A is noncontinuation of the ASA above the ARM junction. Type B is continuation of the ASA above and below the ARM junction. (ARM artery of Adamkiewicz; ASA anterior spinal artery.) not significantly different in the dissection group and nondissecting group (Table 1). Data on the patients who underwent surgical operations are presented in Table 2. Eighty-seven (73%) of 120 patients underwent surgical operations; thoracoabdominal aortic aneurysm repair in 32 patients (including stent-grafting in 1 patient), descending thoracic aortic aneurysm repair in 55 (including stent-grafting in 24 patients). Paraplegia did not occur in any of the patients in whom the ARM was detected preoperatively by MRA (Table 3). Sixteen elective thoracoabdominal or descending thoracic aortic aneurysm operations were performed in Comment Spinal cord ischemia still occurs in 5% to 15% of patients undergoing extensive thoracoabdominal aortic aneurysm repair [1 4], despite many efforts to reduce the rate of paraplegia or paraparesis. Spinal cord injury generally results from temporary or permanent interruption of spinal cord blood supply. There is almost always a dominant anterior medullary artery in the thoracolumbar region, which is called the ARM. The ARM supplies most of the blood to the anterior spinal artery, which perfuses the anterior two thirds of the spinal cord. In anatomical studies, the ARM was found to originate from the left side in 72% [16] to 78% of patients [17], between Th8 and L1 levels in 91% of patients [16], and between Th7 to L1 levels in 94% of patients [17]. The results of the present study concur with the results of those studies. Koshino and colleagues [16] reported that there was no significant correlation between the diameter of the ARM and the diameters of the intercostal artery and lumbar artery from which the ARM originated. Furthermore, within the Th8 to L1 vertebral level, the diameters of the intercostal artery and lumbar artery varied considerably and did not correlate with the diameter of the ARM [16]. Morishita and coworkers reported that the ASA was continuous in adult cadavers and that there was a discrepancy between the ASA diameters above and below the ARM. Furthermore, distal spinal blood supply becomes progressively dependent on the ARM as the narrowest point of the ASA becomes narrower [17]. The morphology of the ASA at the ARM junction, as revealed by MRA, in patients in whom the Adamkiewicz artery was detected was classified into three types. Since we could not measure the size of the ASA by MRA, the three types of ASA morphology were determined according to whether there was continuation Table 3. Comparison of Postoperative Results by Graft Replacement or Stent-Graft Insertion in Patients in Whom the Artery of Adamkiewicz Was Detected by Magnetic Resonance Angiography and in Those in Whom it Was Not Patient and Operation ARM Not Detected ARM Detected Patient No Paraplegia Mortality Patient No Paraplegia Mortality Thoracoabdominal aortic aneurysm Graft replacement Stent-graft insertion Descending thoracic aortic aneurysm Graft replacement Stent-graft insertion Total ARM artery of Adamkiewicz; No number.

5 CARDIOVASCULAR 850 KAWAHARADA ET AL Ann Thorac Surg MRA EVALUATION OF SPINAL CORD BLOOD SUPPLY 2004;78: Table 4. Clinical Outcomes in Patients in Whom the Artery of Adamkiewicz Was Detected by Magnetic Resonance Angiography and in Those in Whom it Was Not Thoracoabdominal or Descending Aortic Aneurysm ARM Not Detected n 16 ARM Detected n 71 p Value a Paraplegia Hospital mortality a Fisher s exact test. ARM artery of Adamkiewicz. of the ASA above and below the ARM junction. Noncontinuation of the ASA above the junction of the ARM was visualized by MRA, but continuation was found in some patients, suggesting that there are some patients in whom spinal cord ischemia would not occur even if reattachment of intercostal arteries was not performed. Some surgeons no longer consider reimplantation of the ARM to be the best treatment strategy and now believe it is best to rely on collateral circulation and a short aortic cross-clamping time [18, 19]. Since MRA showed continuation of the ASA above and below the ARM junction (type B) in 20% of the patients, it is possible that spinal cord ischemia will not occur in such cases even without ARM reconstruction. However, the pattern of the ASA was type A, noncontinuation of the ASA above the ARM junction, in 59 patients (55%). Hollier and coworkers used complete radicular arterial reattachment to prevent spinal ischemia after thoracoabdominal aortic repair [3]. Svensson and associates reported that reattachment of the radicular artery most likely to supply the ARM is important to secure spinal blood supply [20]. They noted that successful reattachment of segmental intercostal or lumbar arteries from Th8 to L1 is important to reduce the risk of paralysis. Therefore, it is very important for us to maintain stable spinal cord circulation achieved by reattaching the intercostal arteries. The problems with the operative strategy of reattaching all intercostal lumbar arteries, including those within the Th8 to L1 vertebral level, are that some of the arteries may not need to be reattached and that reattachment of all of the arteries from Th8 to L1 prolongs clamp time and operation time. A long clamp time may result in spinal cord injury, and a long operation time may result in other postoperative complications. Obviously, an accurate and reliable technique for identifying arteries that need to be reattached is needed. Therefore, reconstruction of intercostal arteries should be planned on the basis of preoperative detection of ARM for distal spinal blood supply. Prevention of the intraoperative steal phenomena (blood flow away from spinal cord circulation) and maintenance of high pressure in the proximal descending aorta may allow sufficient blood flow through the ASA during reconstruction of intercostal arteries in thoracobdominal or descending thoracic aortic aneurysm repair. Catheters may be placed in the orifice of intercostal arteries to control back-bleeding and thereby prevent the intraoperative steal phenomena or alternatively ligation of intercostal arteries by clipping can be performed, if the intercostal artery supplying ARM is identified preoperatively by MRA and excluded as a candidate for clipping. However, Svensson and coworkers [20] reported that a third of neurologic deficits occurred in a delayed fashion and that such delayed complications were closely associated with postoperative hypotension. These findings suggest that postoperative spinal cord circulation is unstable. Therefore, to reduce delayed deficits, we emphasize the importance of stable spinal cord circulation achieved by reattaching the segmental arteries if the ARM can be detected preoperatively. Preoperative detection of an intercostal artery that may be related to the ARM is very useful for establishing the best operational strategy for descending aortic aneurysm or thoracoabdominal aortic aneurysm repair, because surgical repair can be performed while taking care to revascularize the intercostal and lumbar arteries at or near the level of the ARM, and the occurrence of spinal cord injury can thereby be reduced. In our institute, we have routinely reconstructed or preserved an intercostal artery that may be related to the preoperatively detected ARM during operations for repair of thoracoabdominal or descending thoracic aortic aneurysm. Because use of the large carrel patch method can result in expansion of the remaining aortic wall after the operation, we used the interposition procedure for reconstruction of intercostal arteries as the first choice in order to minimize the area of the remaining aortic wall. With this reconstruction method, we think that we may be able to reduce operation time, distal perfusion time and clamp time needed for thoracoabdominal aortic aneurysm repair. In conclusion, preoperative detection of the Adamkiewicz artery is possible by MRA, and detection of this artery is very useful for reducing the incidence of ischemic injury of the spinal cord and noncontinuation of the anterior spinal artery above the junction of the ARM was visualized by MRA. References 1. Cambria RP, Clouse WD, Davison JK, Dunn PF, Corey M, Dorer D. Thoracoabdominal aneurysm repair: results with 337 operations performed over a 15-year interval. Ann Surg 2002;236: Estrera AL, Miller CC 3 rd, Huynh TTT, Porat E, Safi HJ. Neurologic outcome after thoracic and thoracoabdominal aortic aneurysm repair. Ann Thorac Surg 2001;72: Hollier L, Money SR, Naslund TC, et al. Risk of spinal cord dysfunction in patients undergoing thoracoabdominal aortic replacement. Am J Surg 1992;164: Coselli JS, LeMaire SA, Miller CC III, et al. Mortality and paraplegia after thoracoabdominal aortic aneurysm repair: a risk factor analysis. Ann Thoracic Surg 2000;69: Kieffer E, Richard T, Chiras J, Godet G, Cormier E. Preoperative spinal cord arteriography in aneurismal disease of the descending thoracic and thoracoabdominal aorta: preliminary results in 45 patients. Ann Vasc Surg 1989;3: Osterman FA Jr, Mitchell S, Merine D, et al. Angiographic localization of spinal cord blood supply and its relationship to postoperative paraplegia. J Vasc Surg 1991;1:23 35.

6 Ann Thorac Surg KAWAHARADA ET AL 2004;78: MRA EVALUATION OF SPINAL CORD BLOOD SUPPLY 7. Svensson LG. Intraoperative identification of spinal cord blood supply during repairs of descending aorta and thoracoabdominal aorta. J Thoac Cardiovasc Surg 1996;112: Borst HG, Jurmann M, Buhner B, Laas J. Risk of replacement of descending aorta with a standardized left heart bypass technique. J Thorac Cardiovasc Surg 1994;107: Yamada N, Takamiya M, Kuribayashi S, Okita Y, Minatoya K, Tanaka R. MRA of the Adamkiewicz artery: a preoperative study for thoracic aortic aneurysm. J Comput Assist Tomogr 2000;24: Kawaharada N, Morishita K, Fukada J, et al. Thoracoabdominal or descending aortic aneurysm repair after preoperative demonstration of the Adamkiewicz artery by magnetic resonance angiography. Eur J Cardiothorac Surg 2002;21: Fukada J, Morishita K, Hyodoh H, et al. Descending or thoracoabdominal aortic aneurysm repair without intercostal vessel reconstruction using contrast magnetic resonance angiography: report of two cases. Surg Today 2002;32: Takase K, Sawamura Y, Igarashi K, et al. Demonstration of the artery of adamkiewicz at multi-detector row helical CT. Radiology 2002;223: Kudo K, Terae S, Asano T, et al. Anterior spinal artery and 851 artery of Adamkiewicz detected by using multi-detector row CT. AJNR Am J Neuroradiol 2003;24: Kazui T, Komatsu S, Sasaki T, Yamada O. Graft inclusion technique for thoracoabdominal aortic aneurysms involving visceral branches with the aid of a femoro-femoral bypass. J Cardiovasc Surg 1987;28: Tveten L. Spinal cord vascularity. III. The spinal cord arteries in man. Acta Radiol Diagn 1976;17: Koshino T, Murakami G, Morishita K, Mawatari T, Abe T. Does the Adamkiewicz artery originate from the larger segmental arteries? J Thoac Cardiovasc Surg 1999;117: Morishita K, Fujisawa Y, Murakami G, Kawaharada N, Fukada J, Saito T, Abe T. Anatomical study of blood supply to the spinal cord. Ann Thorac Surg 2003;76: Biglioli P, Spirito R, Porqueddu M, et al. Quick, simple clamping technique in descending thoracic aortic aneurysm repair. Ann Thorac Surg 1999;67: Acher CW, Wynn MM. Thoracoabdominal aortic aneurysm. How we do it. Cardiovasc Surg 1999;7: Svensson L, Hess KR, Coselli JS, Safi HJ. Influence of segmental arteries, extent, and atriofemoral bypass on postoperative paraplegia after thoracoabdominal aortic operations. J Vasc Surg 1994;20: CARDIOVASCULAR INVITED COMMENTARY There has been great difference of opinion regarding the importance of reimplanting intercostal arteries. Some aortic surgeons believe this is essential, while others, such as Griepp and colleagues [1], believe that reimplantation makes no clinical difference in paraplegia rates. This dichotomy is based on two schools of thought: The Adamkiewicz school believes that a single artery, usually arising from the T8 to L2 segments, provides segmental blood flow to the lower spinal cord, compensating for the discontinuity in the anterior spinal artery. The gas tank school maintains that no single artery is so important, but rather it is the total amount of blood flow through all intercostal and lumbar arteries that determines adequacy of cord perfusion. For those who believe in the reimplantation of crucial spinal arteries, the identification of the spinal artery or arteries that supply the lower spinal cord assumes critical importance. To achieve reliable, noninvasive identification of these vessels has been somewhat of a Holy Grail in aortic surgery. Contrast angiography has been the gold standard for the identification of the spinal artery, albeit imperfect, with failures and toxicities, including iatrogenic paraplegia from the contrast media injections. This report by Kawaharada and colleagues certainly gains one s attention, because it provides apparently accurate identification of the spinal arteries in a previously unprecedented high proportion (83%) of patients studied and does so noninvasively, by means of magnetic resonance imaging (MRI). The main issue concerning this report is whether it will prove to be reproducible by others. We are given little information about the patients excluded from the study. Could it be that patients likely to image poorly, for example, because of obesity, were excluded a priori? Could there be physical characteristics of the Japanese population which will render these surprisingly good imaging results nonreproducible in Western environments? We hope that these results will indeed prove reproducible, and that routine MRI imaging of the spinal artery becomes a reality. Regardless of one s school of thought, it certainly does not hurt to know the location of the intercostal arteries that provide important blood flow to the spinal cord. Such knowledge can help in many ways. The segment bearing the identified spinal vessel may be spared resection if the aorta is not severely dilated; residual mild dilatation is preferable to paraplegia. Alternatively, a bevel in the resection may preserve the crucial vessel yet still extirpate the neighboring aneurysmal tissue. Knowledge of the location of the spinal vessel may aid in intelligent placement of the lower crossclamp, so that the vital vessel is not excluded from distal perfusion by the left atrial-femoral artery bypass set-up. And, for most surgeons who believe strongly in reimplantation, intelligent selection of implanted vessel(s) can be made in contradistinction to the roulette wheel guesswork implicit without prior vessel identification. Of course, identification of the spinal artery does not equate with good neurologic outcome. There is still the issue of duration of cross-clamping. Identifying in the surgical field the vessels numbered by the radiologist is far from trivial, and reimplantation has risks, including hemorrhage from the side-to-side anastomosis to the main aortic graft. Traction to get to bleeders in this anastomosis can easily lead to the tearing of friable tissue and necessitate the resumption of cross-clamping, with net overall harm by The Society of Thoracic Surgeons /04/$30.00 Published by Elsevier Inc doi: /j.athoracsur