Thoracic outlet syndrome

What is thoracic outlet syndrome?

Thoracic outlet syndrome (TOS) occurs when nerves or blood vessels traveling from the neck toward the arm are compressed. This can cause pain, tingling, weakness, swelling, or changes in circulation. The symptoms and treatment depend on which structure is affected.

The nerves to the arm, called the brachial plexus, pass close to the subclavian artery and vein. These structures travel through narrow spaces near the scalene muscles in the neck, the collarbone, and the first rib. Compression can also occur farther forward, beneath the pectoralis minor muscle near the shoulder.

View larger illustration ↗

Why does compression occur?

Contributing factors may include an extra rib in the neck (a cervical rib), differences in muscle attachments, tight bands of tissue, injury and scarring, or repetitive overhead activity. More than one factor may be involved. An extra rib or an imaging finding alone does not mean that someone has TOS or needs surgery.

Three types, with different symptoms

Identifying the type of TOS is the starting point for care. Some symptoms overlap, and similar symptoms can have causes outside the thoracic outlet.

How is TOS diagnosed?

There is no single test that reliably diagnoses every form of TOS. Evaluation begins with a detailed account of the symptoms, activities that trigger them, prior injuries, and a careful examination. Neck conditions, shoulder disorders, and nerve compression at the elbow or wrist can resemble TOS and may need to be evaluated.[1]

X-rays

Look for a cervical rib, an unusual first rib, or changes related to a previous fracture.

Ultrasound

Assesses blood flow, narrowing, and blood clots when venous or arterial TOS is suspected. Testing may include different arm positions.

Dynamic CT or MRI

A dynamic study takes images with the arms up and with the arms down to look for compression that changes with arm position. These scans also show the relationship of the blood vessels and other structures to the surrounding bones and muscles. The imaging protocol and use of contrast depend on the clinical question.

Nerve testing

Electromyography (EMG) and nerve conduction studies can identify nerve injury or another explanation for symptoms. Normal results do not exclude neurogenic TOS.

Scalene muscle block

A short-acting local anesthetic injection into a scalene muscle may help assess whether temporarily relaxing that muscle improves symptoms. A longer-acting Botox injection is another option for selected patients, as explained below. Neither injection establishes the diagnosis by itself.

Vessel imaging

Venography or arteriography uses contrast to examine a vein or artery, sometimes during a procedure to treat a clot or plan vascular repair.

Tests are selected for the suspected type of TOS; not everyone needs every test.

Botox injection as part of the neurogenic TOS evaluation

As part of the workup for neurogenic TOS, Dr. Servais sometimes refers patients to Lahey Clinic Interventional Radiology for an image-guided injection of botulinum toxin (Botox) into the anterior scalene muscle in the neck. By temporarily relaxing this muscle, the injection serves as a diagnostic aid, helping the team assess whether scalene muscle compression is contributing to symptoms.

If symptoms clearly improve, this can be a strong predictor of a good response to surgical decompression in appropriately selected patients. The result helps guide treatment decisions alongside the history, examination, and other tests. It does not guarantee surgical success, and a lack of improvement does not automatically rule out surgery.[5]

Any relief is temporary. The benefit generally should not be expected to last beyond 3–6 months and may wear off much sooner. The injection may provide short-term symptom relief, but it does not permanently correct the underlying compression.[6]

Treatment begins with the type of TOS

Neurogenic TOS: rehabilitation usually comes first

For most patients, treatment begins with a physical therapist experienced in TOS. Therapy focuses on posture, shoulder mechanics, muscle balance, and modifying activities that provoke symptoms. A consistent program over weeks to months helps the team assess improvement and whether further treatment is needed.

Medication may help manage discomfort while rehabilitation progresses. For selected patients, an anterior scalene Botox injection can help guide treatment decisions and may provide temporary relief. Injections are tailored to the individual evaluation and are not a required step for every patient.

Venous TOS: address the vein and the compression

If a blood clot is present, treatment may include anticoagulation (blood-thinning medicine) and, in selected patients, a procedure to dissolve or remove the clot. Decompression surgery is often recommended to relieve the underlying pressure and reduce the risk of another clot. The sequence depends on the symptoms, timing, and condition of the vein.

Arterial TOS: protect blood flow to the hand

Treatment may require clot removal, repair or reconstruction of the damaged artery, and relief of the compression. An abrupt loss of blood flow can require urgent intervention. Thoracic and vascular surgical expertise may both be needed when planning care.

When is surgery considered?

For neurogenic TOS, surgery may be appropriate when symptoms remain disabling despite a suitable course of nonsurgical treatment and the evaluation supports the diagnosis. Progressive weakness or muscle loss may justify an earlier surgical assessment. Venous and arterial TOS often require a different timetable because of risks to the blood vessels and circulation.

What does decompression involve?

Decompression means creating more space for the affected nerves or blood vessels. Depending on the anatomy, the operation may include removal of the first rib or a cervical rib, division or removal of compressing scalene muscle, and release of tight bands or scar tissue. Neurolysis means freeing a nerve from surrounding tissue; venolysis means freeing a vein.

First-rib removal is an important part of many operations, but it is not necessary in every case. The surgeon chooses the steps needed to address the actual site of compression. Surgery should have a clear goal, such as improving arm function, relieving symptoms, or protecting circulation.

Different ways to reach the thoracic outlet

Approaches include an incision above the collarbone (supraclavicular), below it (infraclavicular), through the armpit (transaxillary), or small incisions in the chest for a thoracoscopic or robotic operation. The need for direct nerve release or blood vessel reconstruction may favor an open or combined approach.

Robotic thoracic surgery

Dr. Servais’s approach to first-rib resection

During robotic surgery, Dr. Servais operates through small incisions in the chest and controls the instruments from a console in the operating room. A magnified, three-dimensional view and instruments with wrist-like movement help him work around the first rib and nearby structures. The surgeon directs every movement; the robot does not operate independently.

The view from inside the chest can provide access along the first rib while avoiding a larger incision in the neck or armpit. The appropriate approach still depends on the type of TOS and the treatment required. If blood vessel reconstruction or extensive direct nerve release is needed, a different or additional approach may be more suitable.

Robotic surgery offers technical advantages, but it has not been established as the best approach for every patient. Long-term comparative evidence is still developing. The priorities are adequate decompression, protection of the nerves and vessels, and a realistic understanding of the expected benefit.

Recovery, risks, and expectations

Recovery depends on the type of TOS, the operation performed, any existing nerve or vessel damage, and your activities. Before surgery, discuss pain control, hospital stay, wound care, lifting, driving, and the plan for returning to work or sport. Patients treated for a clot also need clear instructions about anticoagulation and follow-up vessel imaging.

Rehabilitation remains part of care

Decompression creates space, but recovery also involves restoring comfortable movement and function. Your team will guide the timing and progression of physical therapy. Improvement may be gradual, and some numbness, pain, or weakness can persist. An operation cannot guarantee reversal of longstanding nerve damage.[2]

Risks to discuss with your surgeon

Risks include bleeding, infection, injury to nearby nerves or blood vessels, and problems involving the lung or the space around it. Symptoms may persist or recur, and additional treatment is sometimes needed. Your surgeon will explain how the planned approach and your health affect these risks.[3]

Success is assessed by how you feel and function, and, for vascular TOS, by the condition of the blood vessels. The consultation should include the likelihood of meaningful improvement, the possibility of incomplete relief, and the alternatives to surgery.

Videos & additional resources

Further learning

Surgical education from Dr. Servais. The video includes operative material.

Questions for your visit

1. Which type of TOS do you suspect, and what findings support that diagnosis?
2. What other conditions could explain my symptoms?
3. Do I need additional imaging, nerve testing, or a diagnostic injection?
4. What should my physical therapy program involve, and how will we judge its progress?
5. If surgery is recommended, which structures need decompression and why?
6. Is robotic first-rib resection appropriate for me, or would another approach better address the problem?
7. What improvement is realistic, and what symptoms might persist?
8. What are my individual risks, rehabilitation plan, and expected restrictions after surgery?

Bring a symptom timeline, a list of activities that trigger symptoms, and records of prior physical therapy, injections, imaging, nerve tests, and treatment for any blood clot. These details help the team understand what has already been tried.

Sources & further reading

About this guide

Patient education based on teaching materials by Elliot Servais, MD, FACS, and the references below. This information supports a discussion with your care team and does not determine an individual treatment plan.

Updated October 4, 2026. This guide is general information; your care team can explain which recommendations apply to you.