Thoracic outlet syndrome (TOS) was first defined by Peet et al.⁶⁾ and is now widely used to describe symptoms caused by compression of the brachial plexus, subclavian vein, and subclavian artery at the thoracic inlet⁵⁾. TOS encompasses conditions involving compression in the thoracic outlet that affect the subclavian artery, subclavian vein, and the brachial plexus. TOS is classified based on the structures compressed, as neurogenic TOS, venous TOS, and arterial TOS²⁾. Vascular compression is typically easier to identify with objective vascular imaging²⁾. Neurogenic TOS is the most common form, accounting for up to 98% of cases¹⁾. TOS typically occurs in young and middle-aged adults and occurs three times more frequently in women than in men²⁾.

A major controversy persists among patients with TOS, particularly those who exhibit neurologic-type symptoms such as paresthesia, numbness, and pain, yet lack positive objective tests to confirm the cause²⁾. The lack of professional consensus, coupled with the broad variability of symptoms and the absence of a diagnostic gold standard, frequently leads to misdiagnosis or oversight of this condition^1-5).

Symptoms of neurogenic TOS can vary depending on which trunk of the brachial plexus is most affected but typically include proximal neck and shoulder pain due to muscle imbalance, as well as distal numbness and paresthesia in the upper extremities²⁾. Because each trunk of the brachial plexus originates from cervical spinal nerve roots, it is crucial to differentiate symptoms of neurogenic TOS from neck and upper extremity pain caused by cervical radiculopathy^1-4). Patients with chronic neurogenic TOS and significant concurrent degenerative cervical lesions, which may be mistaken as the cause of their upper extremity pain on imaging studies, are at risk for undergoing unnecessary cervical spine surgery³⁾. A case of neurogenic TOS with asymptomatic multiple cervical stenosis observed on a cervical imaging study is reported.

A 60-year-old right-handed female patient presented with severe pain in the right shoulder and the medial side of the right arm, accompanied by numbness in the hand that had persisted for 2 years. She was a housewife and had played table tennis as a hobby for five years before the onset of pain. Two years prior to presentation, she suddenly developed pain in the upper trapezius area and the deltoid region of the right shoulder. The pain, exacerbated after playing table tennis, significantly disrupted her sleep. It was described as aching and stabbing; the pain in the right shoulder was particularly worse with external rotation of the shoulder. Subsequently, she discontinued playing table tennis and received a diagnosis of frozen shoulder at a nearby rehabilitation clinic, where she underwent regular injections and weekly physical therapy. Despite a year of treatment, her shoulder pain persisted.

One morning, one year prior to presentation, she experienced a marked increase in pain within her right shoulder and deltoid area, which extended to her right upper arm and forearm. Concurrently, she developed severe numbness in her right palm and fingers (Fig. 1). The pain in her right upper arm and forearm was throbbing and burning, radiating down the medial side of her right upper arm and forearm. Subsequently, she experienced numbness in the palm of her right hand and all five fingers. The pain persisted throughout the day, and the burning sensation in her right arm worsened at night. As she lay down at night, the pain in her right deltoid and shoulder region intensified, and she began experiencing a burning sensation, which substantially impeded her sleep. Extension of the neck exacerbated the pain in her right trapezial area. Over time, her right hand became weaker, and she began dropping objects when attempting to hold them. Also, when she abducted her right shoulder, the numbness in her palm intensified, prompting her to use her left hand more often than her right when washing her hair.

She underwent magnetic resonance imaging (MRI) of the cervical spine to investigate right neck and shoulder pain that radiated to her right upper extremity. The MRI revealed cervical spinal stenosis caused by ossification of the posterior longitudinal ligament (OPLL) and disc protrusions (Fig. 2). Despite treatment with gabapentin, non-steroidal inflammatory drugs, tramadol, physical therapy, and multiple cervical nerve blocks, her pain remained uncontrolled. She visited the spine clinic at our hospital with chronic pain in her right shoulder and arm, and weakness in her right hand that was unresponsive to previous treatments. The spine surgeon diagnosed her with cervical radiculopathic pain due to cervical OPLL. However, he noted her right arm pain, which was a burning sensation not typically seen in cervical radiculopathy, and referred her for further evaluation. Electromyography and nerve conduction velocity testing identified a right median nerve entrapment neuropathy, clinically consistent with carpal tunnel syndrome.

Upon examination, her pain was localized to the right side of the neck, including the deltoid, upper trapezius, and interscapular regions. Her right arm pain followed the medial aspect of her upper arm and forearm, aligning with the C8 dermatome. There were no signs of kyphosis or muscle atrophy in the shoulder on physical examination. She maintained a full range of motion in the shoulders, elbows, and hands. However, her pinch and grip strength in her right hand was reduced to a grade 4 (Medical Research Council). The deep tendon reflexes were normoactive. Systemic diseases were ruled out as potential causes of pain, and laboratory tests showed no abnormalities. She rated her pain at 7 or 8 out of 10 on the numerical rating scale.

She noted that her pain worsened significantly at night. She was unable to sleep on her back due to the pain in her right lower cervical and scapular areas, and had to sleep on her side instead. The numbness in her hands also intensified at night. As the pain in her deltoid area increased, so did the burning sensation in her right arm, accompanied by escalating pain in the medial aspect of her right upper arm and axilla. In the Spurling test, interscapular pain intensified with neck extension, but it did not induce a burning sensation in the right arm. As her burning pain was an atypical symptom of cervical radiculopathy and extended over the C8 and T1 dermatomes, a hyperabduction test was performed. Elevating her arm to 180 degrees while keeping her wrist and elbow straight triggered numbness in her right hand and pain on the inner side of her arm within a min. The Adson test yielded negative results.

Plain X-ray of the cervical spine demonstrated decreased lordosis and straightening of the cervical spine. Additionally, mild narrowing was noted in the intervertebral spaces of C5-6 and C6-7. Computed tomography (CT) and MRI scans of the cervical region revealed ossification of the posterior longitudinal ligament at C4-5 and C5-6 (Fig. 2). Furthermore, central disc protrusion and subsequent cervical cord compression were evident at C4-5 and C5-6.

Although her symptoms did not correlate with the imaging findings of the cervical spine, and her pain exacerbated with hyperabduction of the arm, an MRI of the right brachial plexus was warranted. An MRI of the right wrist was also executed, due to persistent numbness in the palm and hand, along with reduced pinch and grip strength. The radiologist indicated that the MRI scan of the right brachial plexus did not reveal any abnormalities in the brachial plexus (Fig. 2C). Nevertheless, the author suspected compression of the right brachial plexus by the scalene anterior muscle. The MRI of the right wrist disclosed palmar deflection of the flexor band and increased signal intensity, coupled with swelling of the median nerve at the carpal tunnel’s entrance, indicative of carpal tunnel syndrome (Fig. 2D). A blockade of the anterior scalene muscle using 5 mL of 2% lidocaine provided temporarily relief from the pain in the right arm and shoulder, lasting about 6 hr.

Given the chronic and persistent pain in the right shoulder and arm unresponsive to medial treatment, along with the clinical history and examination findings suggestive of right-sided neurogenic TOS, and the temporary alleviation of symptoms following a scalene muscle block, surgical intervention to decompress the right brachial plexus and the median nerve at the right wrist was advised over cervical spine surgery. It was conveyed that if her symptoms persisted post-decompression of the brachial plexus, a second cervical decompression might become necessary.

The supraclavicular approach for decompression of the brachial plexus was executed on the right side. The operation took place under general anesthesia with intraoperative neurophysiological monitoring, as described by Mackinnon and Novak⁴⁾. An 8-cm linear skin incision was made two centimeters above and parallel to the clavicle, with subsequent identification and protection of the supraclavicular nerves deep to the platysma muscle. The dissection involved dividing the omohyoid muscles and elevating the supraclavicular fat pad and sternocleidomastoid muscle. During the fat layer dissection surrounding the external jugular vein, transparent lymphatic fluid was observed leaking (Fig. 3A). Further leakage of lymphatic fluid was halted using hemostatic glue. The phrenic nerve was secured in the field of view, anterior to the scalene muscle, revealing that the upper trunk of the right brachial plexus was compressed by the anterior scalene muscle. Notably, the brachial plexus appeared swollen and entrapped between the anterior and middle scalene muscles (Fig. 3B). The anterior scalene muscle was carefully divided using bipolar cautery, preserving the phrenic nerve. This division exposed the middle trunk of the brachial plexus. The long thoracic nerve was meticulously separated from the middle scalene muscle. Subsequently, the middle scalene muscle insertion at the first rib was divided to reveal the lower trunk of the brachial plexus. All tendinous edges of the scalene muscles and the fibrous sheath of the nerve, which could potentially entrap the nerve, were excised while being viewed under a microscope (Fig. 3C). After achieving hemostasis and applying antiadhesion gel, the surgical site was closed in layers, and closed suction drainage remained in place. Subsequently, the transverse carpal ligament of the right wrist was incised, alleviating the compression on the right median nerve (Fig. 3D).

The day after surgery, she reported a marked improvement in the numbness in her right arm and noted a more than 30% reduction in the burning pain on the inside of her right arm. No neurological sequelae were observed postoperatively. The postoperative course proceeded without incident, and the patient was discharged on the 5th day after surgery. Three months post-surgery, the patient reported an over 70% improvement in the burning pain in her right arm and no longer experienced numbness in her hand. Both pinch and grip strength in her hand had completely recovered. However, she still experienced pain in the deltoid and interscapular regions when moving her right shoulder. Seven months post-surgery, the patient reported approximately an 80% reduction in pain in her right shoulder and arm, with pain during shoulder movement no longer impacting her daily activities. At the one-year follow-up, she felt no need for further follow-up. She used gabapentin 300 mg and Ultracet® as analgesics only when necessary, and took the medication for only 7 to 10 days a month as required. There was no sleep disturbance due to pain. Her activities were limited to daily stretching and housework, as she no longer played table tennis.

The diagnosis of neurogenic TOS relies heavily on clinical evidence, particularly when symptoms can be reproduced during dynamic maneuvers, such as arm elevation. However, diagnosing TOS remains challenging and controversial due to the difficulty in objectively quantifying symptoms. Additionally, the presence of cervical spine degenerative pathologies complicates the diagnosis, increasing the risk of unnecessary cervical surgeries. Therefore, recognizing neurogenic TOS, acquiring a thorough medical history, and conducting meticulous physical examinations are critical to avoid the failed spinal surgery syndrome associated with this condition.