Thoracic Outlet Syndrome (TOS) is a complex condition involving the compression of nerves or blood vessels in the narrow space between the collarbone and the first rib. While TOS is most commonly associated with pain, numbness, or tingling in the arm and hand, its symptoms can sometimes include balance issues. This article examines the link between this compression disorder and dizziness, exploring the underlying physiological reasons and management strategies.
Defining Thoracic Outlet Syndrome
Thoracic Outlet Syndrome is a collective term for disorders caused by pressure on the neurovascular bundle that passes through the thoracic outlet, a confined space at the base of the neck. This passageway is bordered by the first rib, the clavicle (collarbone), and the scalene muscles. The structures at risk of compression here are the brachial plexus (a network of nerves), the subclavian artery, and the subclavian vein.
The classification of TOS depends on which structure is compressed. Neurogenic TOS (NTOS) is the most common form, accounting for about 95% of cases, and involves the compression of the brachial plexus nerves. The less common forms are vascular, including Arterial TOS (ATOS), which affects the subclavian artery, and Venous TOS (VTOS), which involves the subclavian vein.
The Direct Link: How TOS Can Cause Dizziness
Dizziness resulting from TOS is generally attributed to two primary mechanisms: vascular compromise and neurological irritation. The vascular theory centers on blood flow to the brain, which is regulated by the vertebral artery, a vessel that branches off the subclavian artery. Compression of the subclavian artery, particularly in ATOS, can indirectly reduce or alter blood flow to the brainstem or inner ear structures responsible for balance.
This alteration in blood flow is sometimes referred to as vertebrobasilar insufficiency, which can manifest as dizziness or vertigo. Compression may also cause a compensatory increase in blood flow to the head via other vessels, leading to symptoms like a feeling of being heavy-headed or dizzy. Even minor changes in the hemodynamics of the head and neck can disrupt the delicate balance system.
The neurological mechanism involves the irritation of the sympathetic nervous system and the brachial plexus itself. The sympathetic nerves run in close proximity to the compressed structures and can be irritated, leading to dysautonomic symptoms that include dizziness. Furthermore, the brachial plexus carries sensory information related to proprioception, which is the body’s sense of position and movement in space.
Compression of these nerves can send distorted signals to the brain, confusing the body’s balance and posture centers and resulting in a sensation of unsteadiness or vertigo. This neurological irritation is often more pronounced in NTOS, the most prevalent form of the disorder.
Distinguishing TOS Dizziness from Other Causes
Dizziness is a common and non-specific symptom that can be caused by many conditions, such as inner ear problems or migraines, making a TOS diagnosis challenging. Dizziness related to TOS is often characterized by its association with specific upper extremity positions and physical activity. Patients frequently report that their dizziness or severe vertigo is exacerbated by changes in neck position or when performing activities that involve lifting the arms.
Dizziness is accompanied by other distinct symptoms of neurovascular compression in the affected arm. These include simultaneous neck pain, arm and hand numbness or tingling, and muscle weakness or fatigue in the upper extremity. In vascular cases, a person might also notice pallor or discoloration in the hand when the arm is elevated, a sign known as the White Hand Sign.
Addressing Dizziness Through TOS Management
Resolution of dizziness relies on successfully treating the underlying neurovascular compression of TOS. Initial management often involves conservative methods, beginning with physical therapy aimed at restoring proper posture and strengthening the muscles surrounding the shoulder and neck. Specific exercises focus on stretching the scalene muscles and improving the mobility of the first rib, which helps decompress the structures within the thoracic outlet.
Anti-inflammatory medications may also be used to reduce localized swelling and irritation of the compressed nerves and vessels. For individuals whose dizziness is linked to muscle tension, therapeutic injections, such as Botox into the scalene muscles, can provide relief by relaxing the muscle and reducing pressure. When conservative measures fail, particularly in severe vascular cases, surgical decompression may be considered. This often involves the removal of the first rib to permanently widen the thoracic outlet space.