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Inlet Arteries or Outlet Veins of the Spinal Cord?

Maastricht University Hospital Maastricht, The Netherlands

 
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Preoperative imaging of the artery of Adamkiewicz has recently received renewed interest due to technical improvements of noninvasive techniques. Localization of this artery is proposed to reduce the risk for development of paraplegia in various surgical interventions. Boll and coworkers [1] showed the potential of MDCT angiography to depict spinal cord vessels and claimed a 100% detection rate for the artery of Adamkiewicz in 100 patients with pancreas neoplasms.

Because spinal cord arteries obey an interindividually variable origin in combination with small calibres, they are difficult to detect. Typical average calibres for the artery of Adamkiewicz are between 0.5 and 1.2 mm [2–4]. Using an in-plane spatial resolution of less than 0.4 mm, Boll et al. [1] convincingly show the visualization of spinal cord vessels.

Outlet veins obey the same spatial (hairpin) configuration as inlet arteries but are up to two times thicker [2, 3]. Outlet veins are consequently more easily visualized than inlet arteries when nonselective contrast administration is used [4]. Without the use of separation techniques, inlet arteries can therefore easily be mistaken for outlet veins.

Theoretically, separation can be achieved on the basis of differences in contrast material arrival. To depict arteries ahead of veins requires very short acquisition times (less than the spinal cord arteriovenous transit time, which is approximately 10 seconds [5]). The combination of high spatial and temporal resolution, which is now technically feasible as shown by Boll et al. [1] (6.2–7.4 seconds), would allow separation of spinal cord arteries and veins. However, separation also strongly depends on appropriate timing of the contrast bolus arrival.

Boll et al. [1] accurately determined the contrast bolus arrival time in the aorta close to the segmental origin of the artery of Adamkiewicz. In our opinion, image acquisition started too late and both spinal cord inlet arteries and outlet veins were already opacified. The segmental artery directly supplying the artery of Adamkiewicz does not represent the only route for contrast material to reach the spinal cord. Additional trajectories include the anterior radiculomedullary arteries deriving from the vertebral arteries, intercostal arteries, interconnections of segmental arteries, and the anterior spinal artery superior to the junction with the artery of Adamkiewicz. Therefore, we think that spinal cord outlet veins in addition to, or in the worst case instead of, inlet arteries were visualized.

Also, other arguments substantiate the covisualization of veins. The calibres of the arteries of Adamkiewicz reported ranged from 0.7 to 2.5 mm (average > 1.3 mm), too large for a nonpathologic spinal cord. Furthermore, in 5% of the patients more than one artery of Adamkiewicz was localized. Additional inlet arteries are smaller sized, in the order of 0.1–0.5 mm [2, 3], which is thinner than reported by Boll et al. [1]. Also, the intradural span was in some cases up to three vertebral levels, which is unusually long for an inlet artery and more indicative of an outlet vein.

In sum, state-of-the-art MDCT offers sufficient spatial and temporal resolution to localize spinal cord inlet arteries and outlet veins. Without differentiation between inlet arteries and outlet veins, detection of the artery of Adamkiewicz remains highly uncertain and is of no benefit for preoperative planning.

References

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1. Boll DT, Bulow H, Blackham KA, Aschoff AJ, Schmitz BL. MDCT angiography of the spinal vasculature and the artery of Adamkiewicz. AJR 2006; 187:1054 -1060[Abstract/Free Full Text]
2. Lasjaunias P, Berenstein A, ter Brugge K. Surgical neuroangiography: clinical vascular anatomy and variations (vol.5 ), 2nd ed. Berlin, Germany: Springer-Verlag,2001 : 73-164
3. Thron AK. Vascular anatomy of the spinal cord. New York, NY: Springer-Verlag, 1988:3 -12
4. Koshino T, Murakami G, Morishita K, Mawatari T, Abe T. Does the Adamkiewicz artery originate from the larger segmental arteries? J Thorac Cardiovas Surg 1999;117 : 898-905[Abstract/Free Full Text]
5. Pattany PM, Saraf-Lavi E, Bowen BC. MR angiography of the spine and spinal cord. Top Magn Reson Imaging 2003;14 : 444-460[CrossRef][Medline]

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				D. T. Boll Reply Am. J. Roentgenol., July 1, 2007; 189(1): W46 - W46. [Full Text] [PDF]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Nijenhuis, R. J. Articles by Backes, W. H. Search for Related Content PubMed PubMed Citation Articles by Nijenhuis, R. J. Articles by Backes, W. H. Social Bookmarking                      What's this?