Cervical ribs (CR) refer to ribs congenitally growing from the seventh cervical vertebrae⁷⁾. CR occurs in approximately 1% of the population and is more common in women than men⁷⁾. Most CRs are asymptomatic; however, 10% cause thoracic outlet syndrome (TOS)¹⁴⁾. If TOS due to CR does not improve with conservative treatment, surgery should be considered¹⁴⁾.

TOS is divided into subtypes depending on the structure that compresses it, such as vascular TOS, which compresses arteries or veins, and neurogenic TOS, which compresses nerves⁸⁾. Most venous TOS compress the subclavian vein, and rare arterial TOS compress the subclavian artery⁷⁾. Vascular TOS usually causes edema and pain in the arms and shoulders. Meanwhile, arterial TOS may not cause radicular pain or numbness. In severe cases, cyanosis may occur with a reduced pulse in the upper limbs¹⁵⁾. Most cases of TOS are neurogenic, and less than 5% are vascular¹⁾. Neurogenic TOS presents with paresthesia, numbness, and motor weakness¹¹⁾.

Herein, we report a case of a patient with a palpable mass in the neck for 3 years and had a tingling sensation in the right arm after 1 year. Radiological examination revealed that CR was compressing the brachial plexus. The patient was successfully treated for CR-induced neurogenic TOS using a supraclavicular surgical approach.

An 18-year-old female presented with a supraclavicular palpable mass 3 years ago and visited an otolaryngology outpatient clinic. For the first time, the C7 rib was discovered (Fig. 1A). Computed tomography (CT) angiography performed 6 months later showed pseudoarticulation between the cervical and first ribs (Fig. 1B, C). The patient started experiencing paresthesia in the C7 dermatome of the right arm after 1 year but had no motor weakness.

Magnetic resonance (MR) imaging of the brachial plexus with enhancement showed that the middle and inferior trunks of the right brachial plexus were compressed between the articulation site of the CR and the anterior scalene muscle (Fig. 2A-D). Also, edema of the middle and inferior trunks of the brachial plexus was suspected (Fig. 2A, C, D). Medication was started for pain control, but there was no improvement in symptoms. Therefore, surgery is recommended. However, as the patient was about to take a college entrance exam, she continued medication treatment and eventually used narcotic analgesics because of severe pain. Surgical treatment can be performed only after a few months.

After general endotracheal anesthesia, intraoperative monitoring was performed to check the somatosensory and motor-evoked signals. The patient was placed in the supine position, and the supraclavicular area was exposed by placing a large roll under the cervical and thoracic spines, with the head turned in the opposite direction.

An incision was made in the supraclavicular fossa (Fig. 3A). We performed a careful dissection of the tissues and muscular, vascular, and nervous structures. First, we identified the omohyoid muscle and the lateral portion of the sternocleidomastoid muscle. Under these conditions, the phrenic nerve was observed on the anterior surface of the scalene muscle, and we found the upper trunk of the brachial plexus. After anterior scalenectomy, we identified the long thoracic nerve, the middle trunk of the brachial plexus, and the subclavian artery (Fig. 3B). The brachial plexus was carefully retracted to reveal the C7 CR posteriorly (Fig. 3C). Finally, the CR was dissected from the proximal end to the distal end and was removed using a longueur, drill, and bone scalpel.

After the operation, the C7 CR was completely removed, as seen on the cervical X-ray (Fig. 4). Immediately after the surgery, the patient's symptoms gradually improved. Radiating pain was decreased, and she was discharged from the hospital on the 15th postoperative day. Symptoms recovered within 2 months after surgery.

TOS is caused by nerve or blood vessel compression of the bone or soft tissue in the thoracic outlet space²¹⁾. According to Atasoy²⁾, TOS is caused by 70% soft tissue and 30% by bony structures. Between 30% and 50% of the soft tissue causes variations in the scalene muscles, compressing the structures within the interscalene triangle¹¹⁾. In addition, soft tissue causes include anomalous ligaments or bands and tumors. Among the causes of bone structure, the CR was the most common. Meanwhile, the fractures of the prominent C7 transverse process and first rib were the second most common. In addition, damage or dislocation of the joint connected to the clavicle and osseous tumors are also related.

Since the diagnosis of TOS is difficult, appropriate examinations and imaging workup are necessary⁷⁾. For physical examination, the elevated arm stress test (EAST), the upper limb tension test (ULTT), the Adson test, the 90° abduction/external rotation stress test (90 AER), and costoclavicular or Halsted tests were used¹⁶⁾. For the EAST, the patient's arms were abducted slightly behind the head at 90°, and the elbows were flexed at 90°. Subsequently, if the patient repeatedly holds and stretches his/her hand for approximately 3 min and the symptoms aggravate, it is a positive response. The ULTT extends both arms 90° with elbow extension, both wrists are dorsiflexed downward and the head is tilted in the opposite direction. If pain or paresthesia occurs, the response is positive. The Adson test involves turning the patient's head toward the symptomatic side, extending the neck, and inhaling deeply. A positive response is observed when the radial pulse disappears⁶⁾. The 90 AER test opens the arm at 90° in external rotation. If symptoms appear, it is a positive response⁷⁾. The costoclavicular or Halsted test is in which the patient lowers the shoulder backward and downward⁶⁾.

Although these tests are widely used, imaging studies are required because of their high false-positive rates⁷⁾. Ultrasonography can be used to image the axillary and supraclavicular areas. It is also useful for checking vascular compression using Doppler imaging and examining the brachial plexus¹⁷⁾. However, if the patient is obese or if the bone overlaps the examination area, the examination is limited¹²⁾. Angiography is the most reliable method for confirming blood vessel compression. However, because it is invasive and cannot identify soft tissue and bone simultaneously, its cause is often unknown⁴⁾. Also, electromyography has low sensitivity in neurogenic TOS. Existing 2-dimensional (D) CT has the disadvantage of showing only the transverse plane; however, 3D CT, which overcomes this, can observe bone and soft tissue more effectively through 3D reconstruction¹³⁾. The 3D contrast-enhanced MR angiography is currently the most commonly used modality to diagnose TOS and can effectively view the vessels and brachial plexus of the upper extremity⁵⁾. The 3D nerve view delay with enhancement used in this case could detect nerve compression more effectively than the previous method, and the cause could be easily identified (Fig. 2C, D).

In neurogenic TOS, conservative treatment can be initially performed first¹¹⁾. Posture correction and weight control are helpful in addition to medication and physical therapy¹¹⁾. Ultrasonography-guided botulinum muscle injections can be attempted, and it has been reported that 69% of symptoms improve within a short period²⁰⁾.

Surgical treatment is considered when conservative care is ineffective, and functional disability occurs. There are three major surgical approaches for TOS: transaxillary, supraclavicular, and posterior approaches^3,11). The most commonly used transaxillary approach has the advantage of completely exposing the first rib and a more cosmetic incision¹¹⁾. Because of this advantage, the neurovascular structure should not be retracted when removing the first rib⁹⁾. However, incomplete exposure of the brachial plexus can cause iatrogenic damage¹⁹⁾.

The supraclavicular approach is used to cut only the scalene muscle or remove the CR in patients with neurogenic TOS¹⁰⁾. Although the supraclavicular approach has fewer cosmetic advantages than the transaxillary approach and is disadvantageous when removing the first rib, the middle and upper trunk of the brachial plexus are easily dissected, and the neck of the first and the anterior and middle scalene muscles are more visible. Because of these advantages, vascular reconstruction is possible^10,11). Terzis and Kokkalis¹⁹⁾ reported that the supraclavicular approach to remove CR had a good prognosis and fewer complications. However, the brachial plexus and vascular structures must be retracted to remove the first rib completely⁹⁾. The complication rate of the transaxillary approach is 22.5%, and that of the supraclavicular approach is 12.6% to 25.9%²²⁾.

The posterior approach is often used in cases of previous anterior neck surgery and TOS recurrence. It also exposed the proximal portion of the brachial plexus. However, a large muscle dissection is required, and this impairs shoulder function¹⁸⁾. In addition, exposure of the proximal part of the brachial plexus can damage the long thoracic, accessory, and dorsal scapular nerves¹⁸⁾.

CR rarely causes symptoms; however, surgery should be performed if necessary. If surgery is considered, a supraclavicular approach that exposes the brachial plexus and surrounding structures is recommended. In addition, when using the supraclavicular approach, it would be helpful to understand the surrounding anatomy and refer to the repetitive surgical images.