The incidence of neurogenic thoracic outlet syndrome is completely unknown, and has been wildly overestimated in the past. Based on a prospectively maintained database at our academic Thoracic Outlet Center, we estimate the yearly incidence of neurogenic and venous thoracic outlet syndrome to be approximately 3 and 1 per 100,000 population, respectively. The ratio of neurogenic to venous thoracic outlet syndrome seems to be approximately 80:20 based on presentation, and 75:25 based on operative correction. These data will help to understand the impact of these disorders, and perhaps help to guide resource management.
Key points
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The ratio of neurogenic to venous thoracic outlet syndrome seems to be approximately 80:20 based on presentation, and 75:25 based on operative correction.
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The incidence of neurogenic thoracic outlet syndrome seems to be approximately 3/100,000 per year, and VTOS 1/100,000 per year.
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The rate of neurogenic thoracic outlet syndrome is approximately the same as that of amyotrophic lateral sclerosis, and much higher than that of cystic fibrosis, to use 2 examples of rare diseases for comparison.
Background
Thoracic outlet syndrome (TOS) refers to 3 general compressive problems that occur at the thoracic outlet: neurogenic TOS (NTOS) exists when the brachial plexus is compressed at the scalene triangle or retropectoral space, venous (VTOS) when the subclavian vein is compressed at the costoclavicular junction, and arterial (ATOS) when the subclavian artery is physically damaged as it passes over the first (or cervical) rib. Despite being recognized for more than a century, the incidence and prevalence of these syndromes are almost completely unknown, in part because of the very subjective nature of the problem and resultant lack of consensus as to diagnosis, poor physician awareness and thus recognition, and the very fuzzy line between physiologic brachial plexus compression and true NTOS.
Again, for all of these reasons, the prevalence of TOS, especially NTOS, is likely unknowable (and not terribly helpful, because this condition is a treatable and usually curable). Although in theory easier to determine, the incidence, at least based on patients with a recognized diagnosis, data, especially with regard to NTOS, are quite sparse. Historically, diagnostic criteria have been widely variable, so much so that the very existence of NTOS has been disputed in the past. , In addition, virtually all reports describe outcomes of those actually treated, and do not provide data based on referrals or untreated patients. For example, 2 recent studies documented the rates of NTOS:VTOS:ATOS to be 97:3:1 and 83:12:3, respectively. These articles , however, were both based on samples only (US National Inpatient Sample and Surgical Quality Improvement Project, respectively), and, obviously, both based on patients undergoing operations only.
A rate that has been extensively quoted is “3 to 80 per 1000 people” (eg, in the first sentence of the preface of the major TOS textbook as well as Chapter 4 in the same text ). It is difficult to identify the source of this quote. Huang and Zager use this number without reference (although earlier in the sentence they reference competing articles by Roos and Wilbourne, who do not delve deeply into this issue). Jones and associates say that “several articles report an incidence of 3 to 80/1000,” but reference only an article from Turkey that gives this ratio without reference. Urschel and Razzuk, in an old textbook chapter, referenced in Wilbourne’s editorial, apparently says that up to 8% of the population has “TOS.” Similarly, in a seminal but also old chapter, Roos describes the incidence of TOS as being between 0.3% and 2% of the population aged 25 to 40. The website Census Reporter estimates that approximately 20% of the current population (of 325,719,178 people) lies within this age range of 65,143,835 people. Even the lower range of Roos’ estimate, 0.3%, yields a total of 195,431 patients in the United States who have TOS, and the higher number, 8%, yields a total of 5.2 million Americans with the condition. Even as an estimate of prevalence, this number does not seem to coincide with reality. It is clear that this is an excellent example of a number essentially created out of thin air that has taken on a life of its own based on repeated citation.
The University of South Florida experience
The senior author (KAI) chaired the Society for Vascular Surgery’s TOS Reporting Standards Committee, which produced a consensus document attempting to objectively define and diagnose the various subtypes of TOS, culminating in a Reporting Standards document published in 2016. The broad concepts and committee consensus was quite firm by mid 2014, and at that time we established a prospective database of all patients who presented to our clinic with possible TOS. This database, maintained until the author left the University of South Florida in 2018, is the basis of this report and our estimates. A full description of methods and more detailed results can be found in our full article.
The database includes all patients seen at our clinic from July 2014 to May 2018, a period of 47 months. As much information as possible, including all subjective clinical information, scoring information, and tentative diagnosis and plan at the time of the office visit was prospectively recorded. Our review was approved by the University of South Florida’s Institutional Review Board; as a retrospective study requirement for consent was waived.
Neurogenic Thoracic Outlet Syndrome
A standardized workup was developed for patients with potential NTOS based on the Society for Vascular Surgery’s recently published reporting standards document. Handedness and occupation were recorded, as was the general history. Note was made of the location of pain and numbness and parasthesias, and which component was dominant. Complaints regarding grip strength weakness, fine motor dysfunction, and headaches were noted, as well as whether arms overhead and driving made symptoms worse. Information regarding duration of symptoms and any prior therapy, as well as any other potentially relevant diagnoses, were recorded. The short form of the Disabilities of the Arm, Shoulder, and Hand and Cervical Brachial Symptom Questionnaire were administered and scores recorded.
On examination, note was made of posture, vascular and sensory status, subjective grip strength (focusing on ulnar function) and the presence of any atrophy. Tenderness to palpation was noted at both the scalene triangle and pectoralis minor insertion site, as well as whether palpation produced distal symptoms. The elevated arm stress test was administered for 1 minute only, and static upper limb tension test performed. Chest radiographs were obtained on all patients who did not already have one.
The level of suspicion was scored by the surgeon and degree of severity by the patient, as either low, medium, or high. After this process, a plan was made, with the options being diagnostic block (usually for those with moderate suspicion), physical therapy, operation, or other.
Vascular Thoracic Outlet Syndrome
Information was gathered regarding the patient’s history and symptom status, including anatomic status at the time of the visit. Patients were categorized as acute having Paget-Schroetter syndrome (PSS) if symptoms had been present for less than 14 days, subacute if 15 days to 3 months, and chronic if longer than 3 months, and with McCleery’s syndrome if positional obstruction only was found, again based on the Society for Vascular Surgery Reporting Standards document. Patients who were seen in the hospital (almost all for acute PSS) were included in this database as new VTOS patients.
Arterial Thoracic Outlet Syndrome
These patients were evaluated based on the status of the artery at the thoracic outlet, the status of the bony thoracic outlet, and the status of the arm distally. Note that ATOS is only diagnosed by the presence of objective arterial pathology.
All information collected, and all subjective information, was recorded prospectively; certain objective information (such as zip codes) were added retrospectively. The following discussion focuses on demographic and incidence information only; our results are discussed more fully elsewhere.
During the 47 months that this database was maintained, a total of 526 patients were referred to our institution with a diagnosis of possible TOS ( Table 1 ). Of these, 432 patients (82%) were referred with symptoms suggestive of NTOS (proximal pain, distal neurologic compromise), 84 (16%) with symptoms suggestive of VTOS (axillosubclavian thrombosis or positional swelling), and 10 (2%) with findings and/or symptoms suggestive of ATOS (objective arterial pathology). Thirty-one patients (6%) presented with symptoms suggesting more than 1 type: 15 with primary VTOS along with distal neurologic symptoms, 12 with primary NTOS along with positional swelling or history of axillosubclavian thrombosis, and 4 with primary NTOS along with objective subclavian arterial pathology.
| Primary Diagnosis | Number | Percent |
|---|---|---|
| NTOS | 432 | 82 |
| VTOS | 84 | 16 |
| ATOS | 10 | 2 |
| Combined | 6 | |
| VTOS > NTOS | 15 | — |
| NTOS > VTOS | 12 | — |
| NTOS > ATOS | 4 | — |
Neurogenic Thoracic Outlet Syndrome
There were 432 patients who presented with suspected NTOS ( Table 2 ), 71% female, with a mean age of 39 ± 14 years. Overall, 85% were judged to have a suspicion for primary NTOS, 8% for recurrent NTOS (recurrent symptoms after a period of improvement after prior intervention), and 1% to 2% for residual NTOS (never having improved after prior intervention), NTOS secondary to prior thoracic outlet decompression for VTOS, symptoms with exercise only, or isolated neurogenic pectoralis minor syndrome. Thirty percent of patients presented with symptom duration of more than 5 years, and the mean symptom duration before evaluation was 60 months.
| Characteristics | ||
|---|---|---|
| Female sex | — | 71% |
| Mean age (years) | 39 ± 14 | Range, 13–84 |
| Type | N | % |
| Primary | 368 | 85% |
| Recurrent | 36 | 8% |
| Residual | 4 | 1% |
| Secondary | 9 | 2% |
| Exercise only | 9 | 2% |
| PMS only | 6 | 1% |
| Duration | ||
| 0–3 mo | 16 | 4% |
| 3 mo–1 y | 108 | 25% |
| 1–2 y | 65 | 15% |
| 2–3 y | 71 | 16% |
| 3–5 y | 27 | 6% |
| >5 y | 129 | 30% |
| Unspecified | 16 | 4% |
| Mean symptom duration until visit: | 60 mo | |
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