Anterior Scalene Syndrome, Manual Muscle Testing and LU 7

Anterior scalene syndrome involves abnormal compression of the brachial plexus between the middle and anterior scalenes located in the interscalene triangle. This condition is part of thoracic outlet syndrome, which is one of three compression sites of this neurovascular bundle. The other two compression sites are under the pectoralis minor within the thoraco-coraco-pectoral (TCP) fascial tunnel and in the costoclavicular region (ST 12 and ST 13 location) where compression is between the clavicle and first rib. Patients with anterior scalene syndrome can complain of a variety of different symptoms such as paresthesia into the shoulder region, into the upper chest, in the region of the rhomboids, levator scapula and/or upper trapezius. Patients may also complain of paresthesia and possibly swelling in the upper limb, forearm and/or hand. It is commonly under-diagnosed condition partly due to a lack of definitive diagnostic tests and because its symptoms can mimic other disorders. (Golden, N., 2021)

Out of the three compression sites, the interscalene triangle, where anterior scalene syndrome is located, is a frequent compression site of the brachial plexus. However, the TCP tunnel located under the pectoralis minor could be argued as equally as frequent in frequency in generating pain. There are provocative exams such as Halstead maneuver and Adson (scalene) maneuver that can help the practitioner hypothesize the patient’s symptoms are coming from a brachial plexus compression in the interscalene triangle and/or TCP tunnel. For anterior scalene syndrome, in addition to the ortho exams, the author uses a manual muscle test to the anterior and middle scalene that can reproduce the patients’ symptoms and determine the contractile ability of these scalene muscles. Shortened, tight as well as lengthened and weak myofascial scalenes fibers can be involved in this compression syndrome. See the video below.

Occupations that require repetitive overhead arm movements or work performed in front of the body for extended periods of time can cause muscle imbalances in the neck and upper extremity that can lead to this condition. Electricians, painters, dental hygienists, desk workers and computer operators often develop increased thoracic kyphosis, forward shoulders and a forward head posture that can predispose the person to compression of the brachial plexus. Interestingly, when assessing patients with these postural deviations, it is easy to observe how the lung’s ability to fully expand is inhibited due to insufficient ribcage and diaphragm motion.

Using traditional Chinese medicine’s channel theory, the Lung’s primary channel directly affects the anterior and middle scalene and can be demonstrated in a manual muscle test to these muscles. The Lung channels internal pathway from where it turns lateral and downward from the laryngeal prominence (Adam’s apple) crosses through the scalenes (anterior and middle) and continues toward and connect to LU 1 (Fig. 1). The Lung’s divergent channel has a superior branch that traverses the supraclavicular fossa and travels through the anterior-lateral throat where these scalenes muscle are located. (Fig. 2). Both channels are strongly influenced by LU 7, the yuan-source point of the Lung channel.

In this video, an anterior and middle scalene manual muscle test is demonstrated on both left and right sides. The patient’s right-side tests weak and is strengthened after needling LU 7. This point can be used with other important acupuncture and motor points and when combined with postural exercises is a very successful combination in treating anterior scalene syndrome.