April- May 2007 Newsletter

TOS is a controversial topic in the literature; many proponents support the existence of the condition, but some strongly vocal opponents doubt the validity of TOS as a medical entity. The primary controversy seems to center around the lack of universally reliable assessments and the confusion with multiple types and clinical presentations. Fortunately, new MRI scanning technology available in many major USA hospitals is now able to accurately identify and localize TOS and other nerve entrapment syndromes. Researchers at Cedars-Sinai Medical Center, the University of California, Los Angeles, and the Institute for Nerve Medicine in Los Angeles, have developed a new nerve imaging technology called ‘Magnetic Resonance Neurography’ which has proven extremely effective in implicating sites of peripheral nerve damage.1

TOS involves compression, injury, or irritation to neurovascular structures at the root of the neck, upper thoracic region, or beneath the pectoralis minor muscle. Compression syndromes at these sites are primarily neurologic and involve the brachial plexus—most often the lower trunk or medial cord. Additionally, the subclavian artery and vein may also be compromised. Cervical nerves and vessels often become trapped between fibrotic anterior and middle scalene tendons as they enter the thoracic inlet (Fig.1.anterior scalene syndrome). Prolonged scalene spasm from injury or overuse can also cause problems as they tug on the first rib pulling it up against a ‘drooping’ clavicle. When the brachial plexus gets squashed between the clavicle and rib, a condition known as costoclavicular syndrome arises. This disorder is one of the leading causes of TOS.

Figure 1

Figure 2

• Intertransversarii fibrosis: Consisting of rounded muscular and tendinous fasciculi running from anterior and posterior tubercles of the transverse processes of two contiguous vertebrae, reflex spasm from cervical joint fixations or facet ‘spurring’ (Figure 5) causes them to tighten and squeeze on spinal nerve roots. An often neglected site of nerve root compression, these tissues are usually easy to release using contract/relax stretching techniques shown in my Myoskeletal Volume III, Shoulder, Arm and Hand videos.
   
• Anterior scalene tightness: Compression of the interscalene space between the anterior and middle scalene muscles frequently causes reflex spasm. This condition is primarily due to long-term nerve root irritation from spondylosis or facet joint inflammation.
   
• Costoclavicular approximation: Postural deficiencies and carrying heavy objects results in neurovascular compression in the space between the clavicle, first rib and musculoligamentous structures.
   
• Pectoralis minor tightness: Repetitive movements of the arms above the head (shoulder elevation and hyperabduction) frictions and irritates the nerve plexus between the pectoralis minor tendon under the coracoid process.

Figure 3

Simply stated, 'double crush' means that if any given nerve is subjected to a proximal compressive neuropathy then it is more prone to the development of a second or 'double' distal neuropathy. Double crush syndrome was first described in the medical journal ‘Lancet’ in 1973. The term refers to a diagnosis of a compressed or trapped nerve in one area (e.g. the neck or thoracic outlet), with a second entrapment in another location (e.g. the carpal tunnel or Guyon's tunnel in the elbow), with both entrapments contributing to symptoms. Some researchers suggest that the presence of an undiagnosed entrapment in another location may explain why some people still experience symptoms after carpal tunnel surgery. This has led manual therapists to question if examination of the hand alone is sufficient when dealing with syndromes such as carpal tunnel. Therapeutic outcomes are more successful when the nerves along the entire length of the arm are examined beginning proximally from the cervicothoracic spine down through the wrist and hand.

Figure 4

Summary
Because the shoulder and neck area consist of very complex body parts with muscles and connective tissues going in all possible directions, therapists must focus intent on correcting postural strain patterns prior to ‘chasing the pain’. A few commonly applied provocation tests for assessing TOS such as the Adson maneuver (scalenes), ‘Hands-up’ (pec minor), Allen (radial pulse) and the Elevation maneuver for costoclavicular canal impingement may be used. These tests may or may not momentarily reproduce symptoms but are sometimes helpful in ruling out other causes which may produce similar symptoms.

Due to the overlapping of symptoms, it’s often difficult to make a definitive assessment using provocation tests. Fortunately, advancements in nerve imagery using Magnetic Resonance Neurography are providing more accurate monitoring of exact sites of peripheral nerve damage. These tests, accompanied by thorough history and postural evaluations are extremely helpful in preventing the formation of adhesions that trap and irritate the nerve bundle that brings sensation to the arm and hand.

Figure 5