Thoracic outlet syndrome (TOS) is a rare condition constituting a diverse array of symptoms that result from compression of the neurovascular bundle exiting the thoracic outlet between the clavicle and first rib. While compression of the subclavian artery or vein can result in aneurysm formation or deep vein thrombosis, respectively, neurogenic thoracic outlet syndrome (nTOS) results from compression of the brachial plexus trunks and is by far the most common subtype of TOS, representing approximately 90%–95% of all cases.1
Symptoms of nTOS typically include shoulder pain, upper extremity pain, neck pain, chest pain, supraclavicular pain, occipital headaches, paresthesias, weakness, and arm heaviness, which are often reproducible with relevant physical activity. The exact distribution of pain can correlate with the dermatomal site of compression of the brachial plexus (upper plexus versus lower plexus). Physical examination findings can include muscular atrophy of the hand, as well as positive findings in the elevated arm stress test or upper limb tension test.
nTOS can be further classified into true or disputed nTOS, with true cases demonstrating objective abnormalities with motor nerve conduction and needle electromyography studies. The majority of nTOS cases are disputed, meaning that patients present with typical symptoms but have seemingly normal nerve conduction.
Conservative management of nTOS includes targeted physical therapy, as well as analgesics such as non-steroidal anti-inflammatory drugs (NSAIDs), opioids, muscle relaxants, and other adjunct pain medications to treat neuropathic pain. Patient who fails conservative management can be considered for surgical resection of the first rib, which generally yields good results.
Despite surgical management, however, some patients may not have satisfactory improvement, or they may have recurrence of their symptoms following initial improvement. Such patients can consider reoperation, but the efficacy of repeat surgery is unknown. Spinal cord stimulation (SCS) as a treatment for this syndrome has been proposed but has not been reported in the literature. We present here a very successful case of SCS for a patient with severe debilitating chronic pain and neurologic symptoms secondary to nTOS.
This article adheres to the applicable Enhancing the QUAity and Transparency Of health Research (EQUATOR) guideline. Informed consent and an applicable written Health Insurance Portability and Accountability Act (HIPAA) authorization form were completed by the patient.
A 17-year-old female cheerleader with no significant medical history presented at our institution for orthopedic evaluation of left shoulder pain. Most notable was a “dead arm” sensation when lifting her arm above her head. Based on additional history, a physical examination, and a shoulder radiograph, she was diagnosed with rotator cuff tendinitis by an orthopedic surgeon.
She presented to a neurologist at age 20 with 6/10 constant shoulder pain with radiation over the ulnar distribution. She had also briefly experienced an episode of chest pain at the onset of her new and worsening symptoms. She had difficulty lifting her arm over her head, which caused numbness and tingling in her fourth and fifth fingers. In addition to a sensation of heaviness in her arm, she also endorsed a weak grip in her left hand. Sensory examination was notable for decreased sensation to pinprick over the dorsum of the left hand, the palmar ulnar distribution (not including fourth and fifth digits) of the left hand, and the deltoid/posterior shoulder region. Light touch, vibration, and proprioception were intact throughout. Physical examination of the neck and upper extremities was otherwise unremarkable. Acetaminophen-hydrocodone was helpful, but NSAIDs, steroids, and extensive physical therapy were ineffective. Due to worsening symptoms, she was unable to continue undergraduate school. Vascular ultrasound studies, magnetic resonance imaging (MRI) of the cervical spine, and extensive electrodiagnostic testing of the left arm were normal.
The patient then saw a vascular surgeon who strongly favored pectoralis minor syndrome (PMS, see Discussion) over traditional TOS, primarily because of tenderness over the coracoid process. The patient also did not have any neck pain with provocative maneuvers, which favored a diagnosis of PMS over nTOS. After further discussion with her surgeon, the patient underwent elective first rib resection by a transaxillary approach. She had significant improvement for a few months but quickly experienced return of her debilitating symptoms. One year following surgery, a repeat radiograph revealed some bony regrowth of the resected rib, and she underwent an additional resection along with partial excision of a hypertrophied middle scalene muscle. This second surgery did little to relieve her symptoms, and she was referred to our pain management center.
Additional electromyography studies continued to be normal. Cervical epidural steroid injection provided no benefit. After psychological evaluation, the patient was deemed a good candidate for SCS. She underwent a 7-day SCS trial with 2 adjacent percutaneous leads placed with the tips at the level of C3. One lead was in the midline and the other slightly to the left side (affected side). Paresthesia was elicited with an external pulse generator (EPG) and multiple programs were offered to her for the trial. During the trial, she tolerated the stimulation well and her pain improved from 5-10/10 to 2-4/10, and she reported significant increase in her activities of daily living. She was able to hold objects in her left hand for longer periods of time, she reduced her intake of oral pain medications, and she had improved sleep. Following this successful trial, she underwent SCS implant (Boston Scientific, Marlborough, MA) with 2 adjacent leads placed in a similar fashion to the trial leads placement (Figure) and an implantable pulse generator (IPG) placed in the left flank below the iliac crest. She tolerated the surgery well and reported marked improvement in her pain (>80% pain reduction), paresthesias, and functional status in subsequent follow-up visits. Over the next 3 years, she rated her pain as 0-2/10. She was able to return to graduate school to pursue her dream in the health care profession and is doing extremely well to this date.
nTOS may arise from various causes. While congenital etiologies such as cervical or anomalous first ribs are readily identified on chest radiographs, other cases may be caused by aberrant scalene musculature or fibro-cartilaginous bands. Traumatic or repetitive use injuries are commonly implicated as well, and overhead repetitive motions of the upper extremities, typically in young individuals who participate in athletic activities (as in this case) can lead to muscle hypertrophy and neural compression.
SCS is traditionally indicated for failed back surgery syndrome and complex regional pain syndrome, among other indications, such as diabetic neuropathy, postherpetic neuralgia, nonoperable critical limb ischemia, and neuropathic pain of the chest, abdomen, or pelvis.2 The use of SCS in cases of nTOS has not been reported, and most patients with nTOS are treated conservatively or surgically.3 Generalizing surgical outcomes for nTOS, however, has been difficult due to the heterogeneity of available studies, lack of generally accepted diagnostic criteria, and clinician dependence on subjective patient reporting. Outcomes for first rib resection procedures seem overall to be good, but quantifying benefit beyond this has proven very difficult.4
To complicate the differential diagnosis, some patients may instead have, or concomitantly have, PMS, a condition in which the more distal neurovascular bundle is compressed underneath the pectoralis minor muscle and anterior to the chest wall. This subclavicular compression is present in up to 75% of patients being evaluated for nTOS.5 Like nTOS, repetitive upper arm movements from physical activity are commonly implicated. One key feature from our patient case that supports a diagnosis of PMS is coracoid tenderness (pectoralis minor tendon insertion). The patient’s other symptoms are consistent with both diagnoses. Because nTOS and PMS often coexist and have very similar symptomatology, addressing both entities is often required. Diagnostic pectoralis minor muscle blocks with local anesthetic and botulinum toxin can be helpful in determining if a patient’s pain is due to, at least in part, compression of the neurovascular bundle beneath the pectoralis minor muscle. A scalene muscle block can also be utilized in a similar fashion to identify supraclavicular nTOS compression. These steps should be considered before proceeding with surgery, repeat surgery, or a cervical spinal cord stimulator.
Because our patient’s nerve conduction studies were normal, she was diagnosed with disputed nTOS with a possible component of PMS as a diagnosis of exclusion. She received temporary relief following rib resection, suggesting that there was compression between the clavicle and first rib. Postsurgical changes, worsening muscle hypertrophy, and concomitant PMS may have all contributed to the development of surgically refractory symptoms. In surgically refractory nTOS patients, neuromodulation may be the only other treatment that can provide satisfactory relief. While SCS has been used successfully for chronic neuropathic pain secondary to brachial plexus injury and brachial plexus root avulsion, the relevance of these reports to nTOS is unknown.
In summary, our patient case of disputed nTOS with possible concomitant PMS failed to respond to medical and repeated surgical treatment. She was successfully managed with SCS for 3 years, which is predominantly characterized by greater than 80% pain reduction, improvement in functional status, and the ability to return to graduate school. This case report provides hope for patients suffering from refractory and debilitating symptoms of nTOS.
Name: Jason E. Hale, MD.
Contribution: This author reviewed the patient’s medical record, summarized the patient’s history and clinical course, performed literature review, wrote the manuscript, and approved the final version of the manuscript.
Name: Jianguo Cheng, MD, PhD.
Contribution: This author is the treating pain management physician who provided intellectual input and relevant clinical context regarding the academic value of this patient case. This author also assisted with writing and editing the manuscript and approved the final version of the manuscript.
This manuscript was handled by: BobbieJean Sweitzer, MD, FACP.
1. Jones MR, Prabhakar A, Viswanath O, et al.Thoracic outlet syndrome: a comprehensive review of pathophysiology, diagnosis, and treatment. Pain Ther. 2019;8:518.
2. Wong SS, Chan CW, Cheung CWSpinal cord stimulation for chronic non-cancer pain: a review of current evidence and practice. Hong Kong Med J. 2017;23:517523.
3. Kuhn JE, Lebus V GF, Bible JEThoracic outlet syndrome. J Am Acad Orthop Surg. 2015;23:222232.
4. Peek J, Vos CG, Ünlü Ç, van de Pavoordt HDWM, van den Akker PJ, de Vries JPMOutcome of surgical treatment for thoracic outlet syndrome: systematic review and meta-analysis. Ann Vasc Surg. 2017;40:303326.
5. Sanders R, Annest SPectoralis minor syndrome: subclavicular brachial plexus compression. Diagnostics. 2017;7e46