What is McCleery syndrome? A guide to this rare vascular condition

As a subtype of venous thoracic outlet syndrome (VTOS), McCleery syndrome is a rare condition defined by the intermittent, non-thrombotic compression of the subclavian vein. For individuals experiencing unexplained and recurrent arm swelling, understanding this distinct vascular issue is essential for proper diagnosis and effective treatment.

Quick Summary

McCleery syndrome is an uncommon condition where the subclavian vein is intermittently compressed in the chest without forming a blood clot, causing arm pain, swelling, and discoloration, especially during activity.

Key Points

• Rare Vascular Disorder: McCleery syndrome is a rare form of venous thoracic outlet syndrome (VTOS) involving subclavian vein compression without blood clots.

• Intermittent Compression: The defining characteristic is the intermittent obstruction of the vein, which worsens with arm movement and improves with rest.

• Distinction from Clots: It is vital to differentiate McCleery syndrome from Paget-Schroetter syndrome, which involves actual blood clot formation in the vein.

• Diagnostic Challenge: Diagnosis can be difficult and often delayed because symptoms are not constant; dynamic imaging like Duplex ultrasound and venography are critical.

• Treatment Options: Management ranges from conservative measures like physical therapy to surgical decompression (e.g., first rib resection) for persistent or severe cases.

• Prognosis: With proper diagnosis and treatment, the long-term outlook is generally very positive, allowing most patients to regain full function and return to activities.

Understanding McCleery Syndrome

McCleery syndrome is a specific, rare form of venous thoracic outlet syndrome (VTOS), named after the researchers who described it in 1951. It is distinguished from other types of VTOS by one critical feature: the compression of the subclavian vein is intermittent and occurs without the formation of a blood clot, or thrombosis. The subclavian vein is a major blood vessel located in the upper chest, responsible for draining blood from the arms back toward the heart. The compression typically happens in a narrow space between the first rib and the clavicle, known as the costoclavicular space.

Unlike Paget-Schroetter syndrome, which is characterized by a definitive blood clot due to chronic compression, McCleery syndrome's symptoms are often positional and transient. This can lead to delays in diagnosis, as symptoms may resolve with rest, making it easy to dismiss or misdiagnose as another condition. This rarity and subtlety make a specialized and dynamic diagnostic approach necessary.

Causes and Risk Factors

The compression responsible for McCleery syndrome is typically caused by anatomical factors in the thoracic outlet, often exacerbated by movement. The primary causes include:

• Muscular Hypertrophy: Overdeveloped or tight muscles, particularly the pectoralis minor or anterior scalene muscles, can crowd the space and squeeze the subclavian vein. This is a common factor in athletes who perform repetitive overhead arm movements.
• Fibrous Bands or Ligaments: Congenital or acquired fibrous tissue can cause chronic compression.
• Anatomical Variants: An unusually shaped first rib or a bony anomaly can predispose an individual to compression.
• Overuse and Repetitive Activity: The condition is frequently seen in younger, healthy individuals who engage in activities that involve repetitive and vigorous arm movements, such as athletes in sports like water polo, swimming, or baseball.

Common Symptoms

Symptoms of McCleery syndrome are often intermittent and linked to specific activities or arm positions. Patients may experience:

• Intermittent swelling of the arm, hand, and fingers.
• Aching or pain in the upper extremity.
• Blush or purple discoloration (cyanosis) of the affected arm.
• A feeling of heaviness or weakness in the arm, especially after activity.
• Visible veins on the chest, shoulder, or arm due to collateral vein development.
• Paresthesia (numbness or tingling) in the arm or hand.

Crucially, these symptoms often subside with rest and worsen with activities involving overhead arm movement or exertion. This positional nature is a key diagnostic clue.

The Diagnostic Process

Diagnosing McCleery syndrome can be challenging due to its intermittent nature and rarity. The process typically involves several key steps:

1. Detailed Patient History: A doctor will take a thorough history, focusing on the triggers for symptoms, such as specific athletic or occupational movements.
2. Physical Examination: A physical exam will evaluate posture, muscle development, and may include provocative maneuvers to reproduce the compression and symptoms.
3. Dynamic Imaging: Unlike standard imaging, which might not show anything at rest, dynamic studies are essential. These include:
   • Duplex Ultrasound: A dynamic duplex scan can show attenuated or stopped blood flow in the subclavian or axillary vein when the arm is placed in an abducted or overhead position.
   • Venography: An invasive procedure using contrast dye provides a detailed image of the vein and can confirm compression during specific arm positions.
4. Ruling Out Thrombosis: Imaging is crucial for confirming the absence of a blood clot, which distinguishes McCleery syndrome from Paget-Schroetter syndrome.

McCleery Syndrome vs. Paget-Schroetter Syndrome

Understanding the difference between these two conditions is vital for proper diagnosis and treatment. Both are types of venous thoracic outlet syndrome, but they differ significantly in their pathology and presentation.

Feature	McCleery Syndrome	Paget-Schroetter Syndrome
Key Pathology	Intermittent compression, no blood clot (non-thrombotic).	Intermittent compression leading to blood clot (thrombotic).
Symptom Onset	Often gradual, worsening with overhead activity.	Typically acute, after a period of strenuous arm activity.
Arm Discoloration	Can be intermittent and bluish.	Can be more persistent, dark blue or purple.
Initial Treatment	Conservative management like physical therapy.	Anticoagulants and thrombolysis to address the clot.
Surgical Timing	Considered if conservative therapy fails.	Performed after treating the acute thrombosis.
Long-Term Risk	Potential risk of developing thrombosis if left untreated.	Post-thrombotic syndrome risk if not treated correctly.

Treatment Options

Treatment for McCleery syndrome is tailored to the severity of symptoms and the underlying cause. Approaches range from conservative management to surgical intervention.

1. Conservative Management: This is often the first line of treatment, especially for muscle-related causes or milder symptoms.
   • Physical Therapy: Specialized exercises can help correct posture, strengthen supportive muscles, and stretch tight ones (e.g., pectoralis minor) to relieve pressure on the vein.
   • Activity Modification: Avoiding or reducing activities that trigger symptoms, especially repetitive overhead motions, is essential.
2. Surgical Decompression: If conservative measures are ineffective or symptoms are severe, surgery is recommended. The goal is to create more space for the subclavian vein by removing a source of compression.
   • First Rib Resection: Removing a portion of the first rib is a common procedure to decompress the thoracic outlet.
   • Scalenectomy/Tenotomy: Removing portions of the scalene or subclavius muscles or tendons may be necessary.
3. Endovascular Procedures: In very rare cases, such as membranous occlusion of the subclavian vein, a balloon angioplasty can be used to dilate the narrowed portion of the vein.

The Outlook for Patients

With a correct and timely diagnosis, the prognosis for McCleery syndrome is generally very good. Many patients, particularly those whose condition is caught early and linked to muscle hypertrophy, can achieve significant relief through physical therapy and activity modification. For those who require surgery, success rates for symptom relief are high. Regular follow-up with a vascular specialist is important to monitor the condition and prevent future complications, including the potential for thrombosis, which can occur if the vein remains under intermittent pressure. This highlights the importance of not neglecting seemingly transient symptoms. For more information on vascular conditions, consult authoritative sources like the National Institutes of Health (NIH).

Conclusion

McCleery syndrome is a rare but important diagnosis in the spectrum of venous thoracic outlet syndromes. Its key distinguishing feature—the absence of thrombosis—sets it apart from more commonly known conditions like Paget-Schroetter syndrome, but also contributes to potential diagnostic delays. For individuals experiencing intermittent arm swelling, pain, and discoloration, especially with overhead activity, consulting a specialist is crucial. Accurate diagnosis via dynamic imaging and a tailored treatment plan, which may include physical therapy or surgical decompression, can lead to excellent long-term outcomes and a return to normal activity.

Frequently Asked Questions

What is the main difference between McCleery syndrome and Paget-Schroetter syndrome?

The main difference is the presence of a blood clot. McCleery syndrome involves intermittent compression of the subclavian vein without thrombosis, while Paget-Schroetter syndrome is characterized by compression that leads to blood clot formation.

What causes the compression in McCleery syndrome?

Compression is often caused by anatomical factors in the thoracic outlet, such as an enlarged pectoralis minor muscle, tight scalene muscles, or other soft tissue abnormalities. It is frequently linked to repetitive overhead arm movements.

Are athletes more susceptible to McCleery syndrome?

Yes, athletes who engage in sports with repetitive overhead arm movements, such as swimmers, water polo players, and baseball pitchers, are at a higher risk.

How is McCleery syndrome diagnosed?

Diagnosis relies on a physical exam and dynamic imaging studies, such as duplex ultrasound or venography, performed while the arm is moved into different positions to reveal the intermittent compression.

What happens if McCleery syndrome is left untreated?

If left untreated, the chronic intermittent compression can lead to damage to the vein's lining, which can eventually result in the formation of a blood clot and lead to Paget-Schroetter syndrome.

What does a dynamic duplex ultrasound for McCleery syndrome show?

A dynamic duplex ultrasound will show attenuated or completely stopped blood flow in the subclavian or axillary vein when the patient moves their arm into a specific overhead or abducted position.

What is the recovery process like after surgery for McCleery syndrome?

Recovery involves physical therapy to restore range of motion and strength. Patients can typically return to their normal activities, including sports, once the recovery is complete.

Can McCleery syndrome occur in both arms?

While it can be unilateral, McCleery syndrome can occur bilaterally. However, studies show it is more often unilateral and can even be asymptomatic in some cases.