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88 m a s s a g e & b o d y w o r k j a n u a r y / f e b r u a r y 2 0 1 8 technique SCIENCE OF NERVES Exploring the Dorsal Scapular Nerve By Whitney Lowe Nerves are particularly vulnerable to compression and tension problems when they pass through narrow tunnels, between closely adjacent structures, or directly through soft tissues. The dorsal scapular nerve (DSN) has a number of sites vulnerable to compression and tension pathology along its path, so let's take a look at where they are and what symptoms they can produce in your clients. The DSN originates from the C5 nerve root along with other nerve fibers that eventually make up the major trunks of the brachial plexus. While the majority of brachial plexus fibers course between the anterior and middle scalene muscles, the DSN goes directly through the middle scalene muscle and then curves around the posterior scalene muscle before heading in a posterior direction toward the upper back region (Images 1 and 2). After curving around the posterior scalene muscle, the DSN descends along the medial border of the scapula. On its way along the medial border of the scapula, it gives out branches to innervate the levator scapulae muscle as well as the rhomboid major and minor. The DSN is a motor nerve, so it is not carrying any significant number of sensory fibers. However, as we will see later, pressure on this nerve can still produce painful sensations even if it is only a motor nerve. POTENTIAL CAUSES OF DSN NEUROPATHY The DSN is susceptible to both compression and tension pathologies at different points along its path. Because it is primarily a motor nerve, the main symptoms from nerve compression or tension are atrophy and weakness of the muscles supplied by the nerve (rhomboids and levator scapulae). The most notable clinical sign that occurs from this nerve signal interruption is winging of the scapula. However, pain in the upper back, shoulders, or arms could also occur as a result of compression or tension pathologies affecting the nerve. Pain in the upper back between the scapulae is one of the most common complaints for clients seeking pain relief through massage treatment. A number of researchers and clinicians are now suggesting that entrapment or impairment of the DSN may be a much more common factor in causing those sensations than previously thought. There are three primary causes of DSN neuropathy: middle scalene nerve entrapment, small nerve branch compression, and dysfunctional feedback loop. 1 Entrapment of the Nerve by the Middle Scalene Muscle The first primary cause of DSN neuropathy is entrapment of the nerve by the middle scalene muscle. The scalene muscles are routinely implicated in nerve compression problems in variations of thoracic outlet syndrome. However, as mentioned earlier, the DSN actually goes through the middle scalene muscle instead of between the middle and anterior scalene muscles. The nerve can become entrapped when the muscle is enlarged (called muscular hypertrophy). In some cases, fibrous bands may run through the muscle, and the rigid edge of these fibrous bands may compress the sensitive nerve. Because the DSN is a motor nerve, neuropathy (pathology of the nerve) most commonly produces muscle weakness or atrophy. It would therefore seem odd that pain would be a primary symptom of nerve compression since this nerve does not carry a significant number of sensory fibers. 1 The dorsal scapular nerve in relation to the middle scalene muscle. Image is from 3D4Medical's Complete Anatomy application. Dorsal scapular nerve (DSN ) Middle scalene

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