Thoracic Outlet Syndrome (TOS) is a group of disorders caused by the compression of nerves or blood vessels in the space between the collarbone and the first rib. This compression can lead to a variety of symptoms, primarily pain and numbness in the extremities. Many patients also report dizziness or vertigo. This article examines the relationship between TOS and the sensation of unsteadiness, which is often a secondary manifestation of the underlying problem.
The Link Between Thoracic Outlet Syndrome and Dizziness
Thoracic Outlet Syndrome can be associated with dizziness, although it is typically not the most direct or primary symptom of the compression itself. The syndrome is broadly categorized into three types: neurogenic (nTOS), venous (vTOS), and arterial (aTOS), depending on which structure is compressed. The majority of cases, about 95%, are neurogenic, involving the brachial plexus nerves. Dizziness is more commonly observed in patients with nTOS due to secondary effects on the cervical spine and surrounding musculature. The link with dizziness is also possible in the less common vascular forms of the syndrome, specifically arterial TOS, if blood flow is significantly restricted.
Physiological Mechanisms Causing Dizziness
The connection between TOS and dizziness is generally explained by two distinct physiological pathways.
Cervicogenic Dizziness
The most frequent link is through cervicogenic dizziness, which stems from dysfunction in the neck. Neurogenic TOS often causes chronic poor posture, such as shoulder drooping, and muscle tension in the scalenes and pectoralis minor muscles. This sustained muscle tightness and poor alignment can lead to a secondary compression or irritation of the upper cervical spine structures. The joints and muscles in the neck contain proprioceptors, which are sensory receptors that provide the brain with information about body position and movement. When the neck is dysfunctional, this proprioceptive input becomes faulty, creating a sensory mismatch with input from the eyes and inner ear, which the brain interprets as dizziness or unsteadiness. This type of dizziness is typically described as light-headedness or a feeling of floating, often exacerbated by neck movement.
Vascular Compromise
A less common, but more serious, mechanism involves vascular compromise affecting the blood supply to the brain’s balance centers. The subclavian artery passes through the thoracic outlet, and while arterial TOS is rare, its compression can influence blood flow. The vertebral arteries, which branch off the subclavian artery and supply the brainstem and cerebellum, can be affected by this compression or by associated cervical spine misalignment. Restricted flow in the vertebral artery due to positional compression can result in vertebrobasilar insufficiency, leading to symptoms like dizziness, tinnitus, and visual disturbances. Conversely, some research suggests that blocking the subclavian artery might divert blood flow toward the head, potentially causing a cerebral hyperperfusion syndrome that also results in vertigo and pressure sensations.
Identifying Accompanying Symptoms
Dizziness related to TOS is often accompanied by other signs of nerve or blood vessel compression in the shoulder region. The presence of classic neurogenic TOS symptoms alongside dizziness is a strong indicator. These include tingling, numbness, or pain that radiates down the arm, often affecting the fourth and fifth fingers. These arm and hand symptoms frequently worsen with positional changes, especially when lifting the arm overhead or carrying heavy objects. Other signs of nerve irritation include weakness or fatigue in the affected arm and shoulder. If vascular structures are involved, accompanying symptoms might include coldness, paleness, or a bluish discoloration of the hand, indicating compromised circulation. Dizziness caused by purely inner ear problems, such as Benign Paroxysmal Positional Vertigo (BPPV), typically presents as a true spinning sensation (vertigo) not accompanied by these distal nerve compression signs. Similarly, migraine-related dizziness generally lacks the specific limb numbness and positional symptom changes that characterize TOS.
Treatment Focused on Symptom Relief
Management strategies for TOS-related dizziness focus on addressing the underlying compression and associated postural issues contributing to neck dysfunction. Conservative treatment, particularly physical therapy, is the first-line approach for neurogenic TOS. Therapies involve exercises designed to strengthen shoulder muscles, improve posture, and stabilize the scapula, helping to open the thoracic outlet space. Specific manual techniques target the release of tight muscles, such as the scalenes and pectoralis minor, which can alleviate the poor neck alignment contributing to cervicogenic dizziness. Postural correction and ergonomic adjustments are also important lifestyle modifications that reduce pressure on the neurovascular bundle. In some cases, injections of muscle relaxants like Botox into the scalene muscles have been shown to provide significant, albeit temporary, relief from vestibular symptoms. Surgical decompression, which involves removing the first rib and/or specific muscle tissue, is reserved for patients who have failed conservative treatment or who have severe, progressive symptoms. If the dizziness is directly linked to severe vascular or neural compression that affects the neck structures, surgical intervention can resolve the underlying cause. However, surgery is not typically performed solely for the symptom of dizziness, but rather as a comprehensive treatment for debilitating TOS.