Suprascapular Nerve - 2
Symptoms:
The main symptom of suprascapular nerve entrapment is deep and diffuse pain poorly localized in the posterior and lateral aspects of the shoulder. The pain is common with many other shoulder problems, making the condition difficult to diagnosis without the aid of applied kinesiology testing. Pain may be referred to the neck, into the arm, or generally to the upper anterior chest, but localized to the acromioclavicular joint. The radial and suprascapular nerves have common root origins with an overlap of radiation down the radial nerve to the region of the common extensor group. Scapular motion aggravates the pain. Usually the patient says that shoulder motion causes the pain, but it is scapular motion and not actually glenohumeral motion that does so.
Examination:
Increased pain can usually be elicited by the examiner applying digital pressure to the supraspinatus muscle in the general region of the suprascapular notch. In chronic conditions there may be atrophy of the supra- and/or infraspinatus muscles.
One of the first steps in evaluating this condition is to simply observe scapular motion. While standing behind the patient have him bilaterally protract and retract the scapulae and observe for symmetrical movement. Further evaluate the movement with arm abduction and flexion.
Have the patient move the arm into the painful position and analyze the shoulder complex motion. There will usually be excessive scapular motion that stretches the suprascapular nerve, especially with flexion or abduction across the chest.
The cross-body arm adduction test is performed by having the patient bring his arm across the anterior portion of his body to bring the scapula maximally around the thorax.5 The scapula protraction increases the total distance of the suprascapular foramen from the cervical spine origin of the nerve. With this movement there will usually be increased irritation of the suprascapular nerve and pain radiation but not in every case of nerve involvement.
The diagnosis is aided by applied kinesiology muscle testing. Test the supraspinatus and infraspinatus muscles. If weak in the clear, return them to normal facilitation by the usual techniques of applied kinesiology. When the muscles test strong in the clear, have the patient protract the shoulder around the thoracic cage and re-test the muscles that will weaken if the suprascapular nerve is irritated as it is stretched by the scapular motion. Take care that the testing position is with the scapula in protraction, not just arm adduction by motion at the glenohumeral articulation.
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The infraspinatus and supraspinatus can be tested in the usual manner with the addition of shoulder protraction. The supraspinatus can also be tested with the starting position at 90° of abduction in the scapular plane (scaption) and internal rotation so the thumb points caudally as described by Jobe and Jobe.3 From this testing position the subscapularis, infraspinatus, and teres minor are, comparatively, electrically silent.
It is important that one understand the mechanics of the shoulder, as examined and treated in applied kinesiology, in order to re-establish synchronous movement and eliminate the stretch exerted on the suprascapular nerve. Usually there is failure of muscular stabilization of the scapula, and its excessive motion stretches the nerve.
The rhomboid muscles are prime stabilizers of the scapula and are often the cause of excessive scapular motion. The rhomboids may need origin/insertion treatment or any one of the five factors of the IVF. A common cause of rhomboid weakness is subtle dorsal scapular nerve entrapment. The dorsal scapular nerve entrapment often accompanies an anterior cervical subluxation at the C5, 6, or 7 level. Associated with the anterior cervical subluxation are hypertonic scalene muscles, weak cervical extensors, and a head forward position. The hypertonic scalene muscles predispose dorsal scapular nerve entrapment as the nerve traverses the scalene muscles. As noted previously, suprascapular nerve entrapment may be associated with working with the arms in abduction. In this position the worker is usually looking up, placing the scalene muscles on stretch to cause additional entrapment on the dorsal scapular nerve causing rhomboid muscle weakness. One may not find weakness unless the patient extends the cervical spine to stretch the scalene muscles.
Organization of the trapezius divisions is paramount to proper organization of the scapula in the shoulder complex motion. The other muscle often involved in disrupted scapula movement is the serratus anterior. Although these muscles are highlighted as probable problems in suprascapular nerve entrapment, the function of the entire shoulder complex needs to be evaluated.
Entrapment within the foramen can be from stenosis by osseous encroachment or a ganglion cyst.8 Kharrazian observed in AK analysis that pressure in the form of a challenge to the transverse ligament, roofing the suprascapular notch, caused generalized indicator muscles to weaken.4 Applying forceful pressure to the ligament for 60 seconds eliminated the positive challenge and strengthened the infraspinatus muscle when tested for suprascapular nerve entrapment. This is found occasionally when stabilizing and organizing the scapula fails to eliminate the muscle weakening with scapular protraction. Kharrazian proposes that the compression at the foramen compresses the blood vessel and causes nerve dysfunction due to ischemia. This would be infrequent because only occasionally do the vein and sometimes the artery run through the foramen.8
Sometimes there is lack of glenohumeral motion, often called a frozen shoulder, that causes excessive scapular rotation in the attempt to obtain adequate arm abduction. The so-called frozen shoulder may be caused by failure of the rotator cuff muscles, such as the supraspinatus and infraspinatus, to contract in a proper temporal pattern. They act as muscle couples to help organize movement of the humeral head in the glenoid fossa as the deltoid abducts the arm. This results in impingement syndrome, and arm abduction is accomplished by increasing scapular rotation, which stretches the suprascapular nerve and potentially irritates it in the suprascapular notch. Neuropathy is created by continued nerve irritation, resulting in greater supraspinatus and infraspinatus muscle dysfunction with more impairment of normal shoulder activity.
Entrapment of the suprascapular nerve must be differentiated from inflammatory conditions of the shoulder. These, too, will cause painful shoulder motion, and the cross-body arm adduction test may be painful. Neuropathy of the suprascapular nerve is often associated with a painful shoulder from other causes. The pain may be a problem in evaluating the shoulder by manual muscle testing, but it can also be a significant asset. Often what appears to be weakness of a muscle due to pain can immediately be eliminated by AK techniques. An example is an apparent weak serratus anterior with severe shoulder pain during the test that is immediately eliminated on retest by therapy localizing the muscle’s origin. The shoulder muscles may give way preventing an effective rhomboid test; applying traction to the neck may strengthen the shoulder muscles allowing the rhomboid muscles to be tested indicating an anterior cervical subluxation.
If neuropathy is severe and has been prolonged, there will be palpable atrophy of the supraspinatus and/or infraspinatus muscles. Some relate this atrophy to disuse because of shoulder dysfunction, rather than to neuropathy. Severe neuropathy of the suprascapular nerve may result in almost total loss of external arm rotation despite normal teres minor action.10