• By Adler Giersch ps

    Thoracic Outlet Syndrome carries with it a host of questions. Diagnosis is sometimes difficult due to the similarity of symptoms between TOS and many other conditions related to traumatic injuries, such as cervical radiculopathy and Carpal Tunnel Syndrome. It can also take time for upper extremity symptoms to develop post-trauma, allowing insurers to challenge the causative relationship between an injury and all of the symptoms.

    TOS is a condition in which the neurovascular bundle passing through the anterior and middle scalenes is compressed. This can cause neck and shoulder pain, upper extremity pain, tingling or numbness and, occasionally, coldness or decoloration of the hand. Compression can affect the nerves only (neurogenic TOS), the subclavian vein (venous TOS) or the subclavian artery (arterial TOS). Neurogenic TOS is, by far, the most common form.

    When a diagnosis of TOS is made, there is a continuum of options regarding appropriate treatment. Conservative care, in the form of chiropractic, massage and physical therapy, is well accepted as the appropriate course of care in the majority of cases. However, when symptoms persist despite these efforts, surgery is looked upon as an option of last resort.

    Patient outcomes following surgery are problematic, particularly with neurogenic TOS (NTOS), in which diagnosis is one of exclusion made primarily through patient reports of symptoms, history, and, more recently, response to scalene muscle blocks. With neurogenic TOS, negative EMG or nerve conduction studies do not rule out NTOS as a diagnosis. In vascular TOS, diagnosis can be confirmed through objective findings of blood flow compromise. Patient selection and operative techniques have been cited as explanations for the differences in patient outcomes. Some studies suggest that a highly selective process for screening surgical candidates is required and improves the rate of successful outcomes.1

    Anesthetic block of the anterior scalene muscles has become a dual-purpose procedure, providing diagnostic confirmation of TOS and as a reliable indicator of which patients may respond favorably to surgery. An anterior scalene muscle (ASM) block entails injection of an anesthetic, such as lidocaine, into the scalene muscles. Relaxation of the anterior scalene muscles via blocks may partially simulate the results of surgical decompression. Additionally, an effective block, where surgery is not an option, can give an indication of the potential use of Botox injections for temporary (3 to 4 months) relief.

    A positive response to anterior scalene muscle blocks using electrophysiological guidance has been found to correlate well with a positive surgical outcome. For instance, one study found that patients with a positive response to an ASM block had a 94% success rate from surgery at approximately 6 months.2

    This study gathered date between November 1993 and November 1995 by reviewing 122 patients who were referred to UCLA Medical Center for possible TOS. Of these, 38 ultimately underwent surgical decompression for neurogenic TOS. Other sources of neck and upper extremity pain were ruled out. All patients had upper extremity symptoms lasting at least one year and had failed a course of physical therapy, occupational therapy, modification of daily activities, muscle relaxants and analgesics. Anterior scalene muscle block with electrophysiological guidance was performed on each. Of the 122 ASM blocks performed, 93 (72%) had a positive result. Twenty patients were ultimately diagnosed with conditions other than TOS.

    Thirty-eight patients underwent surgical decompression. Of those, 30 (79%) reported a good outcome. Of the patients with a positive anterior scalene muscle block, surgery was successful in 30 of 32 cases (94%). Only 3 out of 6 (50%) of patients with a negative ASM block had a good outcome with surgery.

    In this study, a positive ASM block correlated well with the diagnosis of TOS based upon clinical examination and ancillary testing. Patients for whom another diagnosis was established, the ASM block was most often negative (one false positive was identified). Additionally, patients who had a favorable response to the ASM block preoperatively tended to have a good post-operative outcome (94%). This strongly supports the argument that a positive ASM block correlates with good surgical outcome. Though only 50% achieved a good outcome with a negative block, a negative ASM block should not be used alone to rule out a surgical option in appropriate cases. Later studies have found similar results, supporting the correlation between positive ASM blocks and surgical outcomes. ASM blocks have now been elevated to “best practices” in diagnosing TOS and establishing surgical recommendations.

    Despite the studies and “best practices”, insurers will continue to argue that TOS is not a real medical diagnosis or will challenge the symptom array as unrelated to a traumatic event. Patients can easily be outgunned by insurance carriers who will use these arguments to deny treatment or reduce compensation. Victims of traumatic injury should consult with attorneys who understand the insurance industry tactics, as well as the medicine behind the patient’s pain. We at Adler Giersch are available to assist you and your patients with sorting through these issues.

    1 Scali S, Stone D, Bjerke A, Chang C, Rzucidio E, Gooney P, Walsh D. Long-Term functional results for the surgical management of neurogenic thoracic outlet syndrome. Vasc Endovascular Surg. 2010 44:550.

    2 Jordan SE, Machleder HI, Diagnosis of thoracic outlet syndrome using electrophysiologically guided anterior scalene blocks. Ann Vasc Surg 1998:12;260-264.


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