How Anterior Scalene Syndrome Leads to Thoracic Outlet Syndrome

Anterior Scalene Syndrome is one of the three types of of Thoracic Outlet Syndrome (TOS), which is characterized as a condition that affects the nerves, blood vessels, and muscles that pass through the narrow space between the anterior and middle scalene muscles, collarbone and the first rib, as well as the pectoralis minor muscle attachment at the shoulder. It can cause pain, numbness, and weakness in the shoulder, arm, and hand. One of the less common types of TOS is Anterior Scalene Syndrome (ASS), which occurs when the anterior scalene muscle compresses the brachial plexus nerves and subclavian artery against the middle scalene muscle.

In this article, we will discuss the causes, symptoms, diagnosis, and treatment of Anterior Scalene Syndrome. We will also provide some tips for preventing and managing this condition.

Anatomy of the Anterior Scalene Muscle

The Anterior Scalene muscle is a long, thin muscle located in the neck. It attaches to the first rib from the transverse processes of the second to sixth cervical vertebrae. Its primary function is to assist with breathing by elevating the first and second ribs during inhalation. However, when it becomes hypertonic or overactive, it can compress the nerves and blood vessels that pass through the thoracic outlet.

Causes of Anterior Scalene Syndrome

Anterior Scalene Syndrome can be caused by several factors, including:

• Poor posture: Sitting or standing in a slouched position for extended periods can cause the anterior scalene muscle to become hypertonic and compress the nerves and blood vessels.
• Repetitive overhead arm movements: Activities that require repetitive overhead arm movements, such as swimming or throwing a ball, can cause overuse of the anterior scalene muscle and lead to compression of the nerves and blood vessels.
• Trauma: Injuries to the neck or shoulder, such as whiplash or shoulder dislocation, can cause the anterior scalene muscle to spasm and compress the nerves and blood vessels.
• Anatomical anomalies: Some people are born with an abnormal thoracic outlet, which can increase the risk of compression of the nerves and blood vessels by the anterior scalene muscle.

Symptoms of Anterior Scalene Syndrome

The symptoms of Anterior Scalene Syndrome can vary depending on the severity and duration of the compression. Common symptoms include:

• Pain in the neck, shoulder, and arm: The pain may be sharp, burning, or achy and may worsen with movement or activity.
• Numbness or tingling in the arm or hand: The numbness or tingling may be intermittent or constant and may affect one or both arms.
• Weakness in the arm or hand: The weakness may make it difficult to grip objects or perform fine motor tasks, such as buttoning a shirt.
• Swelling or discoloration of the arm: In severe cases, the compression of the subclavian artery can cause swelling or discoloration of the arm.

Diagnosis of Anterior Scalene Syndrome

Diagnosis of Anterior Scalene Syndrome typically involves a physical exam and imaging studies, such as X-rays, MRI, or CT scans. During the physical exam, the healthcare provider may check for tenderness, muscle spasms, or weakness in the neck, shoulder, and arm. They may also perform special tests, such as Adson’s test (TOS Scalene muscles) or the Wright’s Hyperabduction test (TOS in pectoralis muscles), to check for compression of the nerves and blood vessels. Imaging studies can help confirm the diagnosis and rule out other conditions that may cause similar symptoms.

Treatment of Anterior Scalene Syndrome

Treatment of Anterior Scalene Syndrome typically involves a combination of conservative measures and more invasive interventions, depending on the severity and duration of the compression.

Conservative measures may include:

1. Rest and activity modification: Avoiding activities that aggravate the symptoms can help reduce the compression and allow the affected area to heal.

2. Physical therapy: Stretching and strengthening exercises can help improve posture and reduce muscle tension, which can alleviate compression of the nerves and blood vessels.

Pain management: Over-the-counter pain relievers, such as acetaminophen or ibuprofen, may be recommended to alleviate pain and inflammation.

If conservative measures are not effective, more invasive interventions may be recommended, such as:

Nerve or muscle injections: Injecting a local anesthetic or corticosteroid into the affected area can help alleviate pain and inflammation.

Surgery: In severe cases, surgery may be necessary to remove a portion of the anterior scalene muscle or release the compression of the nerves and blood vessels.

 

Prevention of Anterior Scalene Syndrome

Preventing Anterior Scalene Syndrome involves maintaining good posture, avoiding repetitive overhead arm movements, and taking frequent breaks when performing activities that require prolonged sitting or standing. Stretching and strengthening exercises, such as yoga or Pilates, can also help improve posture and reduce muscle tension.

Conclusion

Anterior Scalene Syndrome is a type of Thoracic Outlet Syndrome that occurs when there is compression between the anterior and middle scalene muscles, causing the nerves and blood vessels that pass through the thoracic outlet to be compressed. It can cause pain, numbness, and weakness in the neck, shoulder, and arm. Diagnosis involves a physical exam and imaging studies, and treatment may involve conservative measures or more invasive interventions, depending on the severity and duration of the compression. Preventing Anterior Scalene Syndrome involves maintaining good posture and avoiding repetitive overhead arm movements.

FAQs

Can Anterior Scalene Syndrome be cured?

There is no cure for Anterior Scalene Syndrome, but it can be effectively managed with conservative measures and more invasive interventions if necessary.

Is surgery necessary for Anterior Scalene Syndrome?

Surgery is not always necessary for Anterior Scalene Syndrome, but it may be recommended in severe cases if conservative measures are not effective.

Can Anterior Scalene Syndrome be Preventable?

Anterior Scalene Syndrome can be prevented by maintaining good posture and avoiding repetitive overhead arm movements.

What is the prognosis for Anterior Scalene Syndrome?

The prognosis for Anterior Scalene Syndrome is generally good with appropriate treatment and management.

Can physical therapy help with Anterior Scalene Syndrome?

Yes, physical therapy can help improve posture and reduce muscle tension, which can alleviate compression of the nerves and blood vessels in Anterior Scalene Syndrome.