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Northwestern University Medical School Chicago, IL 60611
We read with interest the study by Remy-Jardin et al. [1] describing findings of helical CT angiography with thoracic outlet syndrome. Their elegant study of 79 patients shows the usefulness of helical CT in portraying this complex anatomic region. Furthermore, their detailed morphometric analysis helps to objectively quantify the functional changes with arm movement in the region. However, we disagree with their claim that this is the first in vivo evaluation of functional anatomy. In fact, several groups of investigators have published findings using helical CT [2], conventional CT [3], duplex sonography [4], and venography with pressure measurements [5]. All of these studies found vascular compromise in patients when the arm was placed under a functional stress. The findings of the larger French study would be better appreciated if discussed in the context of the existing knowledge that it reinforces and builds on.
Our group has also studied helical CT in healthy, asymptomatic volunteers. We found noteworthy compromise of the costoclavicular space, as well as marked venous compression. These findings have been seen in other studies of asymptomatic arms [5,6,7]. We are surprised that Remy-Jardin et al. have discovered a statistically significant difference between the maximum clavicle and first rib distance in their symptomatic patients with postural maneuver, which they did not observe in their healthy, asymptomatic volunteers [1, 8]. This discrepancy may be accounted for by the alternative interpretation: that it is only the minimum distance between the clavicle and first rib that is correlated with vascular compromise, and that symptoms related to overuse occur superimposed on a background of widespread anatomic compression.
The lack of a difference in meaningful measurable parameters between healthy and symptomatic patients is important because it would suggest that these anatomic differences on helical CT scanning are not useful in differentiating patients with and without the thoracic outlet syndrome, and that the assessment of the entire clinical picture remains essential in the diagnosis of these patients. On this latter point, there seems to be consensus among many groups that objective testing and imaging are useful in portraying the anatomy. However, the clinical examination remains dominant because neurovascular compression is common in asymptomatic individuals whether it is measured by physical examination or by expensive diagnostic imaging.
We appreciate the opportunity to comment on this important study.
References
Hospital Calmette 59037 Lille Cedex, France
My colleagues and I read with interest the letter by Matsumura et al. in response to our article [1] on the anatomic characteristics of the thoracic outlet in symptomatic patients. We thank them for providing us with references to several articles, mainly published in the surgical literature and dealing with evaluation of the thoracic outlet in both symptomatic patients and asymptomatic volunteers [2,3,4,5,6].
The apparent misunderstanding concerning the first in vivo evaluation of this region seems to be related to the meaning of "functional anatomy." Our study, using helical CT angiography, was aimed at studying positionally induced modifications of objective measurements of this region in a large group of symptomatic patients. After preliminary experience with asymptomatic subjects, we measured several distances, angles, and vascular diameters before and after postural maneuver and analyzed postural displacement of the vascular structures in 79 patients with clinical symptoms suggestive of thoracic outlet syndrome. Because none of the articles referenced by Matsumura et al. followed a similar study design, our findings could not be compared with the experience of other groups involved in the difficult clinical treatment of thoracic outlet syndromes. Among these references, we read with particular interest the only one that included CT angiography in the evaluation of thoracic outlet syndrome, namely the book chapter written by Matsumura et al. [2], in which we found major similarities in our respective approaches to this syndrome. Unfortunately, that chapter did not include detailed descriptions of findings in the 18 consecutive patients referred to their institution for evaluation of possible thoracic outlet syndrome. However, Matsumura et al. are perfectly correct to underline additional diagnostic approaches to this syndrome, including duplex sonography and venography with pressure measurements [5, 6].
As to the postural changes observed at the level of the costoclavicular space, we must analyze the available data according to the methodology followed in each study. In normal subjects, only two studies can be compared, both using helical CT and published by our respective groups in 1997 [7, 8]. Our study failed to observe any significant difference in the distribution of the measurements on sagittal reformations before and after postural maneuver; Matsumura et al. observed that the costoclavicular distance was reduced by 50% on similar reformats. Measurements of different distances could account for different conclusions in these two studies: One group [7] measured the maximum and minimum distances between the inferior border of the clavicle and the superior margin of the first rib, whereas the other [8] defined the clavicle-to-first-rib distance as the shortest distance between these bones at the lateral convexity of the first rib. Because the subclavian vascular bundle is always located posterior to the narrowest portion of the costo-clavicular space in the neutral position and after postural maneuver, we do not think that the minimum distance between the clavicle and first rib could be correlated with vascular compromise, as suggested by Matsumura et al. in their letter.
Despite discrepancies between our respective results, we would like to emphasize the consensus between our groups concerning the usefulness of CT angiography in the treatment of thoracic outlet syndrome. As previously underlined by Matsumura et al. [2], this technique represents the unique noninvasive means of depicting vascular stenosis, as well as anomalies of the surrounding musculoskeletal structures. In addition, radiologists can provide surgeons with an objective means of evaluating postoperative results [9].
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