Objective Diagnosis (Ulnar Nerve Conduction Velocity) and Current Therapy of the Thoracic Outlet Syndrome

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1 Objective Diagnosis (Ulnar Nerve Conduction Velocity) and Current Therapy of the Thoracic Outlet Syndrome Harold C. Urschel, Jr., M.D., Maruf A. Razzuk, M.D., Richard E. Wood, M.D., Manaharlal Parekh, M.D., and Donald L. Paulson, M.D. ABSTRACT Analysis of 155 operations in 138 patients with thoracic outlet syndrome demonstrates the validity of resection of the first rib as the optimal method of therapy in patients who are not relieved by conservative management. The ulnar nerve conduction velocity (UNCV) study has provided a reliabie, positive, objective method for diagnosis, selection, and evaluation of therapeutic modalities in patients with thoracic outlet syndrome. Median and musculocutaneous nerve compression can be the etiological factor in patients with atypical pain distribution in whom the UNCV is normal. Conduction study of these nerves confirms the diagnosis of thoracic outlet compression. The transaxillary approach allows complete resection of the first rib with decompression of the neurovascular bundle and is associated with a reduced morbidity and hospital stay. mproved diagnostic and therapeutic techniques have significantly advanced the management of patients with thoracic outlet compression of the subclavian vessels and bracnial plexus. Study of ulnar nerve conduction velocity has provided a more objective evaluation of these patients with regard to diagnosis, selection of proper treatment, and assessment of therapeutic results. It is of particular value in the diagnosis of patients with predominantly neural compression, but without actual motor or sensory deficit or bony abnormalities, and in patients with atypical pain distribution, in whom the diagnosis of thoracic outlet compression is more difficult. The purpose of this communication is to analyze the results of operations on 155 extremities in 138 patients selected for surgical therapy from more than 300 patients with thoracic outlet syndrome. Special emphasis is From the Departments of Thoracic Surgery, Baylor University Medical Center and the University of Texas Southwestern Medical School, Dallas, Tex. Presented at the Seventh Annual Meeting of The Society of Thoracic Surgeons, Dallas, Tex., Jan , Address reprint requests to Dr. Urschel, 3810 Swiss Ave., Dallas, Tex THE ANNALS OF THORACIC SURGERY

2 Diagnosis and Treatment of Thoracic Outlet Syndrome placed on the value of the UNCV as an objective method of establishing the diagnosis and evaluating therapeutic results. Nerve Conduction Studies Motor conduction velocities of nerves to the upper extremities can be reliably determined [l, 3, 51. The technique of measuring UNCV has been adapted for clinical use in evaluating patients with nerve compression of thoracic outlet syndrome by Caldwell, Crane, and Krusen [ 11. Conduction velocities over proximal and distal segments of the ulnar nerve are determined by recording the action potentials generated in muscles of the hypothenar eminence. The points of stimulation are over the supraclavicular fossa, the mid-upper arm, below the elbow, and the wrist. The Meditron 201-AD or the TECA B-2 electromyograph employing the coaxial cable with three needle or surface electrodes has been used for the examination in this series. Normal average conduction velocity values of 59.1 m./sec. in the forearm, 55.8 m./sec. around the elbow, and 72.2 m./ sec. through the thoracic outlet have been obtained by this method 111. An average UNCV value of 57.8 m./sec. across the outlet has been observed in patients with thoracic outlet compression [ 11. Clinical Material Of more than 300 patients seen in consultation for thoracic outlet syndrome from 1946 through 1970, 138 patients-116 women and 22 men with an age range of 13 to 65 years (mean 55 years)-underwent surgical treatment. Seventeen had bilateral procedures, making a total of 155 operations. In a previous study, the evaluation of 70 operations in 60 patients through 1967 was reported [lo]. Since then, an additional 85 extremities in 78 patients have been treated surgically and represent the primary consideration in this communication. The previously reported 60 patients are evaluated for long-term results. Signs and Symptoms The symptomatology of thoracic outlet syndrome depends on whether the nerves or blood vessels or both are compressed at the thoracic outlet. In the 138 patients, symptoms of nerve compression were observed most frequently, with pain and paresthesia being present in all but 6 patients and symptoms of weakness in 28 (Table 1). The onset of pain in the majority of patients was insidious and commonly involved the neck, shoulder, arm, and hand; in some, it radiated to the anterior chest or the parascapular area. Paresthesia occurred in specific nerve distributions in 102 patients, with the ulnar nerve being involved in 90% of these patients. VOL. 12, NO. 6, DECEMBER,

3 URSCHEL ET AL. TABLE 1. SYMPTOMS IN 138 PATIENTS WITH THORACIC OUTLET SYNDROME Symptoms No. of Patients Neurological Sensory 138 Pain 135 Paresthesia 135 Specific nerve 102 distribution Motor 28 Vascular Arterial 34 Venous 13 Symptoms of arterial compression were observed less frequently, occurring in only 34 patients. Thirteen individuals presented with symptomatology of venous compression, which included edema, venous distention, and discoloration of the arm. Only 3 patients demonstrated the classic effort thrombosis, or Paget-Schroetter syndrome. Raynaud s phenomenon was observed in 17 patients, all of whom were women. Three patients demonstrated marked poststenotic dilatation or pseudoaneurysm and 1 had subclavian artery occlusion. Objective physical signs were more common in patients with vascular compression than in those with neural disorders. Only 21 patients with nerve compression showed objective sensory changes and 14, muscle weakness, with 5 revealing atrophy (Table 2). At least one of the vascular compression signs was present in all patients-loss of radial pulse with Adson s TABLE 2. PHYSICAL SIGNS IN 138 PATIENTS WITH THORACIC OUTLET SYNDROME Signs No. of Patients Neurological Sensory abnormalities 21 Motor abnormalities 14 Vascular Loss of radial pulse (Adson s test) Hyperabduction Hyperextension Military positions Costoclavicular compression Venous distention & edema Trophic changes Raynaud s phenomenon Temperature changes Subclavian vein thrombosis Arterial occlusion & claudication THE ANNALS OF THORACIC SURGERY

4 Diagnosis and Treatment of Thoracic Outlet Syndrome test, hyperabduction, hyperextension, or military positions. Signs of Raynaud s phenomenon were present in 8 patients, and 8 others were noted to have coldness of the involved extremity. Thirteen patients had venous obstruction, which was observed as edema and venous distention, with 3 showing marked edema and total subclavian vein obstruction. Bony abnormalities were present in approximately 30% of the patients, either as cervical rib, bifid first rib, fusion of the first and second ribs, clavicular deformities, or previous thoracoplasty. The time between onset of symptoms and therapy varied from three days to eight years, with an average of nine months. Diagnosis In addition to the history and physical examination, diagnostic evaluation included neurological consultation, roentgenograms of the chest and cervical spine, and electromyography, with myelography of the cervical spine, arteriography, and phlebography only when indicated. Since 1965, UNCV studies across the thoracic outlet, around the elbow, and across the wrist have been employed in the evaluation of these patients. In 95 extremities studied prior to operation, the UNCV across the thoracic outlet was reduced from the normal value of 72 m./sec. to 53 m./sec. (average), the range being 32 to 65 m./sec. (Table 3). Therapy Most patients treated surgically had had previous physiotherapy ranging from three months to several years. It is important that such therapy be properly performed, since many of these patients receive the same treatment as persons with cervical syndrome, which often exaggerates the symptoms of thoracic outlet compression. Proper physiotherapy includes heat massages, active neck exercises, scalenus anticus muscle stretching, strengthening the upper trapezius muscle, and posture instruction [ll. Since sagging of the shoulder girdle, common among the middle-aged, is a major etiological factor in this syndrome, many of the patients with less severe disease are improved by strengthening the shoulder girdle and improving posture. More than half the patients seen in consultation required no surgical procedure but were TABLE 9. UNCV IN PATIENTS WITH THORACIC OUTLET SYNDROME Velocity (m./sec.) Value Average Range Normal Preoperative Postoperative VOL. 12, NO. 6, DECEMBER,

5 URSCHEL ET AL. improved significantly with conservative management. If the UNCV was above 60 m./sec., most patients were improved by conservative management. However, if it was below 60 m./sec., the majority required surgical resection of the first rib or correction of other bony abnormalities. An operation was performed on 155 extremities in 138 patients, 17 requiring bilateral procedures. Bilateral procedures were usually staged, although they were performed concomitantly in 4 patients. Early in the series, section of the scalenus anticus muscle alone was performed in 26 patients, in 21 of whom the cervical rib was resected through the anterior cervical approach described by Naffziger and Grant [41 and by Ochsner, Gage, and DeBakey [6]. Claviculectomy and insertion of an aorta-to-brachial artery vein graft was carried out in 1 patient. Except for 3 patients who were unavailable, the follow-up period has ranged from seven to twenty-four years. The first rib, with or without a cervical rib, was resected to relieve compression in 128 extremities in 112 patients. Eighty-two resections were performed through the transaxillary approach by a modified technique of Roos [7, 81 and 46 through the posterior approach as described by Clagett [Z]. Concomitant cervical sympathectomy was performed in 5 of these patients. Follow-up of patients operated on through the posterior approach has ranged from six months to eight years; for those with the transaxillary approach, from six months to five years; and for the patient who had claviculectomy and a brachial artery graft, four years. C 1 in i cal R esu 1 ts Results of resection of the first rib, through either the posterior or the transaxillary approach, were superior to scalenotomy alone or in combination with excision of a cervical rib (Table 4). A good result indicates complete relief of symptoms; a fair result, improvement with some residual or recurrent mild. symptoms; and a poor result, no change from the preoperative status. Ninety-six percent of the patients who had first rib resection showed TABLE 4. RESULTS OF SURGICAL THERAPY IN 155 EXTREMITIES IN 138 PATIENTS WITH THORACIC OUTLET SYNDROME Result Procedure Good Fair Poor Total First rib resection (transaxillary approach-82, posterior approach-46) Scalenotomy (no follow-up-3) Aorta-to-brachial artery graft & claviculectomy Total THE ANNALS OF THORACIC SURGERY

6 Diagnosis and Treatment of Thoracic Outlet Syndrome improvement; 107 had a good result and 16, fair. Eight patients with a fair result showed early clinical improvement but developed recurring symptoms requiring physiotherapy one to two years later. There were 5 failures following rib resection, and 2 patients required cervical disc removal early in the series, before myelography was used. Three other patients had causalgia. There was no significant difference in long-term result between patients who had rib resection by the transaxillary approach and those operated on through the posterior approach. In contrast, only 15 of the patients who had scalenotomy maintained long-term improvement, with 6 good and 9 fair results. The patient who had claviculectomy and a brachial artery graft did well. In the group of patients with significant vascular compression, resection of the first rib has provided uniform success in improvement of symptomatology. In the group with predominantly nerve compression, two general categories have been observed: In the first group were patients with the classic syndrome involving pain and paresthesia in the ulnar nerve distribution of the arm and hand, pulse diminution as elicited by one of the various compression tests, and slowing of the UNCV below 60 m./sec.; 95% of these patients improved with resection of the first rib. In the second group were those patients who had demonstrated the atypical pain distribution often associated with cervical syndrome secondary to whiplash injury or trauma, who may or may not have had pulse changes on the compression tests, and who had less slowing of the UNCV than did patients with the classic disease but were failures of long-term physiotherapy. Although most patients in the second category were significantly improved by resection of the first rib, which was employed in some instances as a therapeutic trial, all the failures and fair results in this series came from this group alone. Postoperative UNC V Studies UNCV studies have been performed postoperatively in 79 extremities over a period ranging from two hours to five years, with an average of four months, and have demonstrated an average increase in velocity of 18 m./sec., the largest increase being 42 m./sec. In 5 patients there was no significant improvement in conduction velocity. In 1 patient with the classic syndrome, the preoperative UNCV was 32 m./sec. Two hours postoperatively it had increased to 58 m./sec., two days later to 65 m./sec., and two weeks later to 74 m./sec. This represented the most rapid improvement following decompression in the series, the patient being completely relieved of symptoms. In another patient, who developed a significant postoperative hematoma, the UNCV changed from 53 m./sec. preoperatively to 60 m./sec. six months after operation, then dropped to 58 m./sec. one month later, to 50 m./sec. in another month, and finally to 44 m./sec. two weeks after that. Three months later it had increased to 60 m./sec., then to 69 m./sec. after three more VOL. 12, NO. 6, DECEMBER,

7 URSCHEL ET AL. TABLE 5. CORRELATION OF UNCV AND CLINICAL STATUS IN PATIENTS WITH THORACIC OUTLET SYNDROME Average UNCV (m./sec.) Clinical Result Preoperative Postoperative Good Fair Poor months, and finally to 73 m./sec. three months after that. The patient was symptomatic when the UNCV was below 60 m./sec. and has become asymptomatic since it increased to above 70 m./sec. A high correlation between UNCV and the clinical status was observed (Table 5). Patients who had a good result following operation had had a preoperative UNCV average of 51 m./sec. and showed return to a normal average of 72 m./sec. postoperatively. In those who had a fair result, the preoperative UNCV had averaged 60 m./sec. and increased to an average of only 63 m./sec. postoperatively. In the poor result group, the preoperative average of 61 m./sec. slowed to an average of 58 m./sec. postoperatively. Fortynine of 64 patients who had a good result showed an increase of more than 12 m./sec., with only 4 showing an improvement of less than 6 m./sec. In contrast, all but 1 of the poor result patients studied showed an increase of less than 6 m./sec. There has been no hospital mortality. Morbidity included clinically insignificant pneumothorax in 18 patients, hematoma in 2, and infection in 1 patient. Morbidity has been reduced by use of the transaxillary approach, as evidenced by a reduction in the average hospital stay from six days for those operated on by the posterior approach to three and one-half days for those treated through the transaxillary approach. Less pain and an almost rapid return to full range of shoulder motion has been apparent in the transaxillary group. Comment UNCV study has markedjy facilitated recognition of the thoracic outlet syndrome, particularly in patients with predominantly nerve compression symptoms. Whereas previously, many primary pain problems in the upper extremity were diagnosed as cervical syndrome or shoulder-hand syndrome, now accurate assessment and precise localization of compression at the thoracic outlet can be made on an objective basis. A UNCV of less than 70 m./sec. across the outlet is consistent with thoracic outlet compression. If the conduction velocity is 60 m./sec. or greater, but less than THE ANNALS OF THORACIC SURGERY

8 Diagnosis and Treatm.ent of Thoracic Outlet Syndrome m./sec., most patients can be managed successfully with conservative but specific physiotherapy. If the conduction velocity is less than 60 m./sec., the majority of patients require surgical intervention and removal of the first rib with correction of any significant bony abnormality. Selection of patients for operation has been improved by this test as compared with previous methods, which frequently involved operation as a therapeutic trial with diagnosis being made only by exclusion. The diagnosis of carpal tunnel syndrome or ulnar entrapment at the elbow can be readily established with this technique, and, depending upon the significance of the slowing in conduction, the proper lesion can be treated with priority. Postoperative testing of ulnar nerve conduction has provided, for the first time, an excellent objective test for evaluating clinical results. A significant increase in UNCV occurs following rib resection in most patients who show clinical improvement. The UNCV and the clinical course have a close correlation. A failure to improve clinically has usually been correlated with a minimal or no improvement in the UNCV. Significant early improvement in the clinical status and UNCV, followed by recurrence of clinical symptoms with concomitant slowing of the conduction velocity after a period of one to two years, suggests either scarring or recurrent outlet compression. This has been the case in 8 of our patients. In the classic group, patients who had an ulnar distribution of pain and paresthesia radiating from the neck to the hand, with loss of radial pulse on the various compression tests and a UNCV reduced below 60 m./sec., excellent results have been obtained with resection of the first rib. The second group of patients who had atypical pain distribution, with or without radial pulse diminution on compression tests and a less reduced UNCV (60 m./sec.), and who had failed to respond to prolonged conservative therapy has produced most of the clinical failures, although some good and fair results have been obtained. Although the ulnar nerve is the one most frequently involved in this syndrome, others such as the median nerve can also be compressed. Swank and Simeone [9] described pain distribution in the deltoid area and lateral aspects of the limb (C5 and C6). A normal UNCV in such patients should not negate the diagnosis of thoracic outlet compression. Conduction studies of the musculocutaneous or median nerves may reveal low velocities which would affirm the diagnosis of compression. The transaxillary approach has been effective in accomplishing complete resection of the rib with decompression of the neurovascular bundle. Complete removal of the rib, including its neck and head, is important to avoid postoperative irritation of the nerve roots (C8 and T1) which are adjacent to the neck of the rib. Failure to remove the head and neck of the rib may compromise the results of therapy. Particular attention to the anatomical relation of the C8 and T1 roots to the first rib and the close proximity of the long thoracic nerve to the scalenus medius muscle is important in order to avoid inadvertent injury to these nerves, since exposure is limited. VOL. 12,,No. 6, DECEMBER,

9 URSCHEL ET AL. Acknowledgment We are deeply indebted to Drs. Caldwell, Crane, and Krusen for their standardization of the ulnar nerve conduction philosophy for clinical use, careful preoperative and postoperative evaluation of patients treated surgically, and help with the preparation of this manuscript. We are also indebted to Mrs. Nancy Braden and Mrs. Jane Suess for typing and editing the manuscript. References 1. Caldwell, J. W., Crane, C. R., and Krusen, U. L. Nerve conduction studies: An aid in the diagnosis of the thoracic outlet syndrome. Southern Med. J. 64:210, Clagett, 0. T. Presidential address: Research and prosearch. J. Thorac. Cardiovasc. Surg. 44: 153, Jebsen, R. H. Motor conduction velocities in the median and ulnar nerves. Arch. Phys. Med. 48:185, Naffziger, H. C., and Grant, W. T. Neuritis of the brachial plexus mechanical in origin: The scalenus syndrome. Surg. Gynec. Obstet. 67:722, Nelson, R. M., and Currier, D. P. Motor nerve conduction velocity of the musculocutaneous nerve. Phys. Ther. 49:586, Ochsner, A., Gage, M., and DeBakey, M. Scalenus anticus (Naffziger) syndrome. Amer. J. Surg. 28:699, Roos, D. B. Transaxillary approach for first rib resection to relieve thoracic outlet syndrome. Ann. Surg. 163:354, Roos, D. B., and Owens, J. C. Thoracic outlet syndrome. Arch. Surg. (Chicago) 93:71, Swank, R. L., and Simeone, F. A. The scalenus anticus syndrome. Arch. Neurol. Psychiat. 51:432, Urschel, H. C., Jr., Paulson, D. L., and McNamara, J. J. Thoracic outlet syndrome. Ann. Thorac. Surg. 6:1, Discussion DR. CHARLES CRANE (Dallas, Tex.): With the increasing availability throughout the country of electromyographic and nerve stimulation techniques, we want to give information about what can be expected from these determinations. For example, of approximately 5,000 electromyographic determinations done each year at our institution, we are finding about 200 to 300 individuals who have abnormal nerve conduction through the outlet area. So this is a very prevalent condition, often associated with postural changes or with so-called whiplash or cervical syndrome. Our approach with these patients consists of a straight electromyographic determination using a needle electrode to rule out, first of all, cervical nerve root compression. This is followed by nerve conduction determinations as discussed in this particular paper. Almost any peripheral nerve, regardless of its location in the body, can be adequately studied by nerve conduction techniques. What we are 616 THE ANNALS OF THORACIC SURGERY

10 Diagnosis and Treatment of Thoracic Outlet Syndrome looking for are areas of compression. We electrically stimulate the nerves at the wrist, below the elbow, above the elbow, and in the supraclavicular area. This allows us to determine if there is an area of compression or entrapment at the wrist, the elbow, the axillary area, or in the thoracic outlet. We would also study the median nerve at the wrist to rule out the possibility of carpal tunnel syndrome; interestingly, there is apparently a high correlation between carpal tunnel and thoracic outlet syndrome. After checking the median nerve at the wrist, we would also look at the pronator area for entrapment at this level. We use surface electrodes for the nerve conduction determinations, thereby assuring a very painless procedure which is located over the hypothenar area. In addition, we stimulate the area above the clavicle. We also use a ground plate and a stimulating unit which supplies a very minimal electric current. From this, you get a brief idea of what we would determine with the studies. As mentioned, these individuals need a good course of physiotherapy. Our belief is that physiotherapy should consist of moist heat to the paracervical area, massage, and a good exercise program, including range-ofmotion activities for the neck, scalene muscle stretching, upper trapezius muscle strengthening, postural instruction, and, in some individuals, cervical traction. We think that UNCV determination in this particular condition serves as an aid in diagnosing the problem, provides assistance for the surgeon in predicting the outcome of the surgical procedure, and also serves as a guide for the surgeon during the postoperative management stage. DR. MILTON V. DAVIS (Dallas, Tex.): Those of us who had the privilege of learning to do a standard thoracoplasty under competent instruction and then had this followed by some experience have died hard when it comes to adopting the transaxillary approach. I now think that the transaxillary approach is the approach of choice. The statements about morbidity I do not doubt, but I think each of us has to look at this very critically in his own series. It takes excellent assisting to give the surgeon adequate exposure to do the operation through the axilla, not that it does not take excellent assistance to help the surgeon in anything he does. But this excellent assistance occasionally involves some pulling on the arm, and I think it is capable of giving at least some strain or some ischemia to the brachial plexus. In our own series, smaller than that of Dr. Urschel and his associates, we have had 1 infection, which could be happenstance but at least is a higher incidence than we have had with other incisions. Two points seem worthy of mention. First, a cervical rib can be removed concomitantly with the first rib through a transaxillary approach, and this approach does lend itself very well to the removal of a cervical rib. VOL. 18, NO. 6, DECEMBER,

11 URSCHEL ET AL. The second point relates to the anatomy of the first rib and its transverse process. I really prefer to remove the rib in its entirety, partly because that is an old habit; but also I think it gives you a lot of mobility. There is a joint, with ligaments, at the end of the transverse process and at the vertebral body. The point I want to stress is this: In young persons who are as supple as a sapling waving in the breeze, this whole operation is pretty easy, especially if they are slender. But if there is spinal arthritis or significant thickening of the ligaments, the operation can be difficult no matter which approach you use. We really think that the head of the rib should come out in every case, and we prefer not to bite the rib out piece by piece but to take it down with a good subperiosteal dissection. In the area from the tip of the transverse process to the body, you are only insinuating an instrument between the transverse process and the rib that you are taking out. It is a safe area. When you get down to the body, it is a little frightening because there is a nerve root a few millimeters away; but this is why we think the head must come out. Just one little technical point: If you twist the rib with the alligator rib grabber and it does not give, then try the little curved (about 5 mm.) bone curette. It fits well around the head of the rib and frees the joint easily. DR. RUSSELL M. NELSON (Salt Lake City, Utah): I agree that an objective means of assessing these patients is needed. In our experience they have been to many doctors, in the vast majority of instances have had multiple procedures, and I think they must have an objective procedure. We are grateful for Dr. Urschel s presentation. We have not had the means for determining ulnar nerve conduction time available to us in our area, so we have depended upon arteriography. Arteriograms done before and after first rib removal emphasize that obstruction to the subclavian artery is best demonstrated by abduction and external rotation of the extremity, with the head turned away from the abducted extremity. I agree with Dr. Urschel in thinking that the majority of these patients are best treated without surgery, using the postural maneuvers explained by Dr. Crane. We are not capable of getting the same kind of exposure that Dr. Urschel demonstrated through the transaxillary approach and use a different route: Through a small incision about 6 or 7 cm. in length the cartilage of the first rib is exposed. The cartilage is removed after first dissecting free the greater curvature of the first rib. After the cartilage is resected, the anterior and then the medial scalene muscles are detached. Then with strippers one can get the other muscular attachments free and accomplish the rib excision with a Sauerbruch-Frey first rib shears, which are very helpful for that maneuver. 618 THE ANNALS OF THORACIC SURGERY

12 Diagnosis. and Treatment of Thoracic Outlet Syndrome DR. JOHN J. NOLAN (Arlington, Va.): I want to compliment Dr. Urschel on his very beautiful presentation. There is one small point, however, that I wish to make in discussing compression syndromes; and that is that we wish to relieve them permanently. I notice that in the technique presented, subperiosteal resection of the rib was performed, leaving the periosteum behind to regenerate bone. As we all know, some of the late pain syndromes that occur following rib resection are due to regeneration of bone by the periosteum. The periosteum, the surgeon s greatest friend, provides a nice cleavage plane. It is more difficult to remove it. Nevertheless, I think that an important technical aspect of this operation does involve removal of the periosteum. DR. W. GERALD RAINER (Denver, Colo.): I have enjoyed Dr. Urschel s presentation and think that he and his group deserve a great deal of credit for pursuing the investigation of nerve conduction velocities in evaluating patients with symptoms of thoracic outlet compression. This group of patients may be puzzling indeed, and any reliable objective test that may help clarify their situation is most welcome. In cooperation with Dr. George Twombly, head of Physical Medicine at St. Joseph Hospital in Denver, we have performed 48 paired studies in 28 patients. The method used was identical to that described by Drs. Urschel and Crane, namely, stimulation of the ulnar nerve at Erb s point. Dr. Urschel did not mention whether his testing was performed with the patient s arm in a position of abduction; we routinely measure velocities in all patients with the arm in a neutral position and again with the arm abducted. The resultant values and relative change in velocity in our series nearly duplicated those presented by Dr. Urschel; however, our values tended to be somewhat lower, which may simply reflect a minor variation in the testing equipment or method of testing. Nerve conduction velocities across the thoracic outlet on the right measured an average of 62.1 m./sec. (range, ) with the arm in a neutral position and 54.2 m./sec. (range, ) in the abducted position. Positional velocity delay ranged from 3.0 to 19.0 m./sec. (average, 8.0 m./sec.). On the left side, average neutral velocity was 55.0 m./sec. (range, ) and average abduction velocity was 51.9 m./sec. (range, ). Velocity delay on the left side ranged from 2.0 m./sec. to 11.0 m./sec., with an average of 4.0 m./sec. In 1 patient, who had recurrent symptoms two years after resection of the first rib, positional subclavian arteriography was normal. A nerve conduction delay of only 2 m./sec. led to reexploration, which revealed a scarred, fibrosed medial scalene muscle severely compressing a portion of the brachial plexus. Prompt relief of symptoms was achieved by section of the taut muscle. We still rely primarily upon positional subclavian arteriography for diag- VOL. 12, NO. 6, DECEMBER,

13 URSCHEL ET AL. nostic help in patients suspected of having thoracic outlet compression but are turning more frequently to nerve conduction time studies, especially in problematic cases and in those patients with recurrent symptoms. DR. URSCHEL: I appreciate the comments and am deeply indebted to each of the discussants, particularly to Dr. Crane and his associates for all their help in this field. The paper by Drs. Caldwell, Crane, and Krusen has been published in the Southern Medical Journal. It describes the technique for measuring ulnar nerve conduction velocity, which has provided, for the first time, an objective method for diagnosis and evaluation of therapeutic results in these patients. Drs. Caldwell, Crane, and Krusen have also described specific physiotherapy that often differs from routine conservative management and more frequently provides symptomatic relief. The priority in treating a patient with both carpal tunnel and thoracic outlet syndrome should be determined by the symptoms and the conduction velocities. Often, surgical relief of one condition is all that is necessary to provide relief of the other. Dr. Davis has the same problem as many of my patients, in that he likes to see the rib in toto at the end of the operation. This is much more difficult through the transaxillary approach and, I believe, entails much greater risk of damaging critical structures. I think many of the stretch neuritis problems, which we rarely see, that he worries will result from pulling on the arm are related to the fact that the rib is removed intact through a small hole. We worry, as does Dr. Nolan, about leaving the periosteum behind, as it may be responsible for some of the failures or recurrences in our series. However, if the periosteum is taken with the rib, there is a greater risk of damage to the adjacent structures through the transaxillary approach. I would agree with Dr. Nelson about angiography in the patient with an unusual vascular problem; however, this occurs rarely in our experience. 620 THE ANNALS OF THORACIC SURGERY