Thoracic Outlet Syndrome: Why Your Arm Goes Numb and Weak

Pressure on the nerves traveling through the thoracic outlet can cause numbness and weakness in your arm. Symptoms may worsen when you lift your arm, carry heavy objects, or repeatedly reach overhead. Depending on the type of compression, you may also notice swelling, skin discoloration, or a cold feeling in your hand.

At Total Orthopedics & Sports Medicine, our doctors locate the area of compression and assess which movements trigger your symptoms. Since thoracic outlet syndrome can mimic neck, shoulder, or peripheral nerve conditions, we carefully distinguish the source of symptoms before starting treatment. This helps us avoid unnecessary treatment while addressing the specific problem affecting your arm function. Call 855-321-6784 to arrange your consultation with our specialists.

How Does Thoracic Outlet Syndrome Lead to Arm Numbness and Weakness?

Thoracic outlet syndrome can lead to arm numbness and weakness by compressing the nerves that travel between your neck and arm. This compression disrupts normal nerve signals, which can affect sensation and muscle control. As a result, you may notice difficulty with gripping, lifting, or other repeated arm movements.

Here are the common factors that can lead to nerve compression in the thoracic outlet:

1. Cervical Rib and Other Anatomical Differences

Some people are born with an extra rib in the neck, called a cervical rib; an unusual first rib; or a tight band of tissue near the nerves. These anatomical variations can narrow the space where the brachial plexus passes toward your arm. When the nerves pass through this limited space, the extra rib or tissue may compress them. In fact, a review reported that up to 20% of neurogenic thoracic outlet syndrome (TOS) cases are caused by the presence of a cervical rib.

2. Tight or Enlarged Scalene Muscles

The scalene muscles are located along the sides of your neck, near the nerves that travel into your arm. When these muscles become enlarged, tight, or scarred, they can reduce the space available for nearby nerves. This narrowing can add pressure on the brachial plexus as it passes between the scalene muscles. Repeated overhead activity or previous neck trauma may further increase this pressure.

3. Repetitive Overhead Activity

Frequent throwing, swimming, lifting, or other repetitive overhead motions can repeatedly stress tissues around the nerve pathway. Over time, this stress may cause muscle enlargement, small tissue injuries, and fibrosis. These changes can narrow the available space around the nerves. As a result, people who regularly perform overhead activities may develop numbness, tingling, weakness, and other neurological symptoms.

4. Trauma and Scar Tissue

A neck or shoulder injury can reduce the space around the nerves that travel into your arm. For example, whiplash or a fall may cause swelling and inflammation around these nerves. As the injury heals, scar tissue may develop around the nerves, narrowing their pathways. A healed collarbone or first-rib fracture can also change the shape of the nerve pathway, increasing pressure on the nerves.

5. Posture and Shoulder Position

Changes in posture can alter the position of your shoulder blades and collarbone, which may reduce the space available for the nerves passing into your arm. Tight or imbalanced muscles around the neck and chest can further increase pressure on these nerves. Therefore, prolonged poor posture may increase nerve compression when the thoracic outlet is already narrowed by a cervical rib or tight muscles.

Where Does Thoracic Outlet Compression Occur?

Thoracic outlet compression occurs in the narrow passage between the base of your neck and upper chest (thoracic inlet). The brachial plexus and major blood vessels travel through this region before entering your arm. Because space in this region is limited, tightness or enlargement of nearby muscles can compress these nerves and blood vessels.

Along this pathway, compression can develop at three main locations:

• Between the Scalene Muscles: These neck muscles surround the pathway of the brachial plexus and subclavian artery, so tightness can increase pressure on them.
• Between the Collarbone and First Rib: A limited thoracic outlet space between these bones can compress the nerves and blood vessels traveling into your arm.
• Beneath the Pectoralis Minor Muscle: This chest muscle can place pressure on the nerves and blood vessels passing beneath it.

What Are the Different Types of Thoracic Outlet Syndrome?

Neurogenic, venous, and arterial are the three main types of thoracic outlet syndrome. Neurogenic TOS affects the nerves, while venous TOS affects a major vein, and arterial TOS affects a major artery. The resulting common symptoms can vary according to the structure affected by the compression.

Here is how each type differs based on the structure affected and its typical symptoms:

• Neurogenic Thoracic Outlet Syndrome: Nerves responsible for muscle control in your arm are compressed, causing symptoms such as numbness, tingling, pain, and weakness.
• Venous Thoracic Outlet Syndrome: Compression affects the subclavian vein, which can cause arm swelling, heaviness, bluish discoloration, and sometimes a blood clot.
• Arterial Thoracic Outlet Syndrome: Narrowing around the subclavian artery can reduce blood flow into your arm or hand, resulting in cold sensation, pale skin, or pain.

According to a review of thoracic outlet syndrome, neurogenic TOS is the most common type, representing more than 90% of cases. In contrast, venous TOS occurs in approximately 3% to 5% of cases, and arterial TOS occurs in about 1% cases.

Why Does Lifting Your Arm Worsen Symptoms?

Lifting your arm can worsen thoracic outlet syndrome symptoms because the overhead position may narrow the space available for nerves and blood vessels. This repetitive arm motion may increase pressure on these structures and interfere with normal nerve function or circulation. As a result, numbness, tingling, weakness, pain, or swelling may become more noticeable.

For example, everyday tasks such as reaching for a high shelf, washing your hair, or lifting objects above shoulder level may trigger your symptoms. Similar symptoms may occur during swimming, throwing, or other activities that repeatedly require you to raise your arms. In these situations, symptoms may gradually increase and improve once you lower your arm.

How Can Ongoing Numbness Affect Hand Strength?

Continued nerve compression can disrupt the signals that control the muscles in your hand, gradually reducing grip strength. With continued compression, you may notice difficulty gripping objects, opening jars, or performing other precise hand movements. In severe cases, prolonged nerve dysfunction can lead to visible muscle wasting at the base of the thumb.

In addition, numbness can interfere with the sensory signals traveling from your hand and fingers to your brain. Reduced sensory feedback about pressure and position can make it difficult to judge how firmly you are holding an object. A prospective study of 85 patients with neurogenic TOS also reported a 30% reduction in grip strength in symptomatic hands compared with healthy controls.

Can Long-Term Compression Cause Muscle Loss?

Yes, long-term nerve compression can cause muscle loss when ongoing pressure disrupts the nerve signals that activate your muscles. Without normal nerve stimulation, the affected muscles may gradually lose size and strength. Over time, ongoing compression may lead to more noticeable muscle atrophy and reduced hand function.

Why Do Symptoms Usually Affect Only One Arm?

Symptoms usually affect only one arm because the nerves or blood vessels on that side are under pressure. An extra rib, tight muscles, or a previous injury can further narrow the space around the nerves or blood vessels. Then, this localized pressure can cause numbness, weakness, pain, or swelling in the arm on that side.

Who Has a Higher Risk of Thoracic Outlet Syndrome?

People who perform repeated arm movements, overhead activities, or have an extra rib may have a higher risk of thoracic outlet syndrome. Repeated overhead use can place ongoing stress on the muscles and tissues surrounding the thoracic outlet. A previous neck or shoulder injury may also cause swelling or scar tissue that narrows the thoracic outlet.

Other risk factors that may increase your chances of developing thoracic outlet syndrome include:

• Poor Posture: Forward-head and rounded-shoulder positions can reduce the thoracic outlet space.
• Heavy Lifting: Repeated heavy lifting can place additional strain on the neck and shoulder muscles.
• Neck Muscle Tightness: Tight scalene muscles can reduce the space available for nearby nerves and blood vessels.
• Age and Physical Activity: Young, active adults may be at higher risk of venous TOS, especially men aged 20-30.
• Occupational Physical Strain: Jobs involving frequent lifting, carrying, pulling, or overhead work can repeatedly strain the muscles around the thoracic outlet.
• Pregnancy: The postural changes that occur during pregnancy may increase pressure within the thoracic outlet.
• Tumors or Masses: A growth near the thoracic outlet can occasionally compress nearby nerves or blood vessels.

What Is the Difference Between TOS and Cervical Radiculopathy?

Thoracic outlet syndrome develops when pressure affects the nerves or blood vessels traveling through the upper chest toward the arm. On the other hand, cervical radiculopathy results from compression or irritation of a nerve root in the neck. Both conditions can cause arm pain, numbness, or weakness, but the location and source of compression are different.

Doctors can help distinguish these conditions by evaluating the pattern of symptoms and the movements that trigger them. For example, holding your arm overhead may trigger TOS symptoms, while turning or bending your neck may worsen cervical radiculopathy. A physical examination can also help identify whether the compression is located near the thoracic outlet or at a cervical nerve root.

Can Carpal or Cubital Tunnel Cause Similar Symptoms?

Yes, carpal and cubital tunnel syndromes can cause numbness, tingling, and weakness similar to thoracic outlet syndrome. However, these conditions involve a trapped nerve at the wrist or elbow rather than compression near the neck and upper chest. Because the location of compression differs, the pattern of symptoms in the upper limbs may also vary.

Can More Than One Nerve Be Compressed at Once?

Yes, more than one nerve can be compressed at the same time. This may occur when pressure develops at different points along the nerve pathway. For example, a nerve may be affected near the thoracic outlet and again at the elbow or wrist. This can cause overlapping numbness, tingling, pain, or weakness.

When the same nerve pathway is compressed at two different locations, doctors may describe it as double crush syndrome. The effects of compression at both sites can overlap, making it difficult to identify which problem is causing symptoms. As a result, treating only one area of compression may not fully relieve your symptoms.

How Do Doctors Identify the Source of Arm Numbness?

Doctors evaluate the thoracic outlet syndrome pain pattern and location to identify the affected nerve and the possible area of compression. Then, they compare these findings with muscle strength, reflexes, and symptom-triggering movements. These findings help determine whether the symptoms originate from the neck, thoracic outlet, elbow, or wrist.

Furthermore, the extent of sensory changes can help differentiate between specific nerve pathways in the upper body. Symptoms affecting the thumb, index, and middle fingers may indicate median nerve involvement. In contrast, numbness in the ring and little fingers may suggest ulnar nerve involvement.

Which Tests Can Help Confirm the Diagnosis?

Doctors may use imaging tests, nerve conduction studies, and vascular tests to diagnose thoracic outlet syndrome. X-rays or other imaging can identify anatomical causes of compression, while nerve tests assess nerve function. Similarly, ultrasound or vascular imaging can assess blood flow through the arteries and veins of the affected arm.

Since nerve compression at different locations can cause similar symptoms, it can be difficult to identify the source of your arm symptoms. Without a clear diagnosis, treatment may not address the problem responsible for your ongoing numbness or weakness. Therefore, our spine specialists examine the cervical spine and neurovascular structures and use diagnostic tests to locate the source of persistent numbness. Book your evaluation for an accurate thoracic outlet syndrome diagnosis.

Does Thoracic Outlet Syndrome Always Require Surgery?

No, thoracic outlet syndrome does not always require surgery. In fact, a study of 150 patients with neurogenic TOS showed that 27% of patients improved with nonsurgical treatment. However, if non-surgical treatments do not provide enough relief, doctors may recommend decompression surgery to address ongoing nerve or blood vessel compression.

Here are the common nonsurgical treatments doctors recommend for managing TOS:

• Activity Modification: Reduces repetitive overhead movements that trigger symptoms.
• Posture Adjustments: Improves positions that may increase pressure around the thoracic outlet.
• Pain Medications: Helps manage pain and inflammation.
• Muscle Relaxants: May reduce muscle spasms and tightness that contribute to symptoms.
• Targeted Injections: Botox injections may help relieve symptoms in some neurogenic cases by reducing muscle tightness that contributes to compression.
• Clot-Dissolving Drugs: For venous TOS complicated by a blood clot, doctors may use clot-dissolving drugs along with other treatments.

For patients who require surgery, doctors select the procedure based on the structure causing the compression. For instance, doctors may perform first-rib resection, scalene muscle release, or cervical rib removal to relieve compression. Additionally, in the case of vascular thoracic outlet syndrome, doctors may perform vascular repair or reconstruction to restore normal blood flow.

Which Activities Should You Avoid During Recovery?

During recovery, avoid heavy lifting, repetitive overhead movements, and activities that repeatedly trigger arm pain, numbness, or weakness. These activities can place additional strain on the healing tissues around the thoracic outlet region. You can gradually return to these activities as your recovery progresses and your symptoms improve.

You should also limit contact sports, forceful pushing or pulling, and exercises that place significant strain on your neck and shoulders. Other than that, carrying a heavy bag on one shoulder may increase pressure around the thoracic outlet. Therefore, follow your doctor’s guidance before returning to any restricted activities.

What Are the Risks of Delaying Treatment?

Without timely treatment, ongoing compression from thoracic outlet syndrome can gradually worsen your symptoms. If pressure on the nerves continues, you may develop increasing weakness, loss of sensation, muscle wasting, and other neurological disorders. Similarly, ongoing compression of blood vessels can restrict circulation and increase the risk of blood clots in the affected arm.

For arterial TOS, reduced blood flow may lead to serious complications, including limb ischemia or an arterial aneurysm. A 30-year study also reports that delaying vascular surgery increased the risk of recurrent blood clots that restricted blood flow to the arm. In addition, a study on venous TOS reported that ongoing pressure can damage and narrow the affected vein, increasing the risk of a blood clot.

Important: Vascular complications may require urgent treatment if circulation to the affected arm is significantly reduced.

How Long Does Thoracic Outlet Syndrome Take to Improve?

Thoracic outlet syndrome often improves within 6 to 12 weeks with nonsurgical treatment. In fact, a study of 220 patients with neurogenic TOS reported improved pain and arm function after a three-week inpatient rehabilitation program. In comparison, recovery after surgery may take about 3 to 6 months.

For example, a study of 70 patients with neurogenic or venous TOS evaluated recovery at 3, 6, 12, 18, and 24 months after surgery. Among patients who returned to full-time work or activity during follow-up, half had returned by four months and 75% by five months. During this time, symptoms of thoracic outlet syndrome may gradually decrease as treatment helps relieve pressure on the affected nerves or blood vessels. However, recovery time can vary depending on the severity of compression and your response to treatment.

Can Nerve Function Recover After Treatment?

Yes, nerve function can recover after treatment once pressure on the affected nerves is relieved. With nerve recovery, symptoms such as numbness, tingling, and weakness may gradually decrease. But prolonged compression can cause permanent nerve damage, which may limit full recovery of sensation and strength.

Here’s how doctors track nerve recovery after thoracic outlet syndrome treatment:

• Physical Exam: Checks muscle strength, reflexes, and hand movements for signs of improvement.
• Grip Strength Testing: Measures changes in hand strength as the affected nerves recover.
• Sensory Testing: Helps determine whether the affected nerves are regaining normal sensation.
• Nerve Conduction Studies: Measure how effectively electrical signals travel through the affected nerves.

When numbness improves but hand weakness persists, it can be difficult to know whether your nerve is still recovering or needs further treatment. At Total Orthopedics & Sports Medicine, our specialists compare changes in sensation, strength, and hand function to determine how your recovery is progressing. Based on these findings, we can adjust your treatment plan to protect nerve function and relieve symptoms. Consult our doctors today to assess your nerve recovery.

How Can You Lower the Risk of Symptoms Returning?

To lower the risk of symptoms returning, avoid repetitive movements that increase pressure on the thoracic outlet and maintain proper shoulder posture. You should also perform recommended stretching and strengthening exercises to support your neck and shoulders. As your strength improves, gradually return to overhead activities to avoid excessive strain on the affected area.

In addition, the following precautions may help reduce the risk of symptoms returning:

• Avoid Prolonged Arm Elevation: Avoid prolonged activities that keep your arms elevated above your shoulders.
• Modify Repetitive Work Tasks: Change the position, frequency, or technique of tasks that repeatedly trigger arm symptoms.
• Avoid Aggressive Neck Stretching: Forceful stretching may irritate sensitive nerves when symptoms have not fully resolved.
• Watch for Vascular Symptoms: Seek medical care if you notice new arm swelling, discoloration, unusual cold sensation, or sudden pain.
• Follow Return-to-Sport Guidelines: Ensure shoulder strength and range of motion have recovered before resuming overhead training.

Book Your Appointment for the Treatment of Thoracic Outlet Syndrome! 

Thoracic outlet syndrome can make it difficult to work, exercise, or complete routine tasks that require regular use of your arm. If symptoms persist, you may start limiting these activities without knowing which movement triggers them. A proper evaluation can help identify the source of your symptoms and guide treatment that addresses the underlying problem.

At Total Orthopedics & Sports Medicine, our specialists first use the least invasive treatment to safely treat your condition. But if symptoms continue despite initial treatment, we reassess your condition and adjust treatment based on your recovery progress. From your initial evaluation through follow-up visits, we provide ongoing support focused on your recovery goals. Call 855-321-6784 or visit our Linden clinic today to schedule your appointment.

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