Clinically, shoulder and cervical spine problems frequently overlap. Cervical radiculopathy and shoulder pathology can both create neck, upper back, shoulder and arm pain, as well as motor and sensory changes. At times, the diagnosis is evident and easily pinpointed; however, other times the causative ideology is not clear even with a thorough history and examination. Let’s follow the process to determine if there is a “go-to test” for the differential diagnosis.
The good news is this diagnostic dilemma is in the chiropractic wheelhouse because it is nerve related. It can be related to the nerve roots, peripheral nerves, referred pain or even the vertebral subluxation complex.
Kasuura mentions there is a growing amount of evidence to support that rotator-cuff tears are related to neurologic dysfunction occurring in the cervical spine, especially in the case of cervical spondylosis. The rotator-cuff muscles, shoulder girdle, several cervical muscles, and portions of the arm and hand are all innervated from C4-7. For example, C5 nerve root irritation can create sensory changes, motor changes or just be painful anywhere from the neck to the hand. Plus, a torn supraspinatus tendon can present as weakness in shoulder abduction with pain referring as far as the elbow, just like a C5 nerve root compression.
In addition, the cervical apophyseal joints can create cervical, upper back, shoulder and upper arm pain – adding another layer to the differential diagnosis.
Pain Transmission
Pain perception is complex and a review of the physiology of pain transmission helps in our assessment of pain patterns. Somatic pain transmission occurs through two pathways. The “fast” pathway is transmitted by myelinated A-delta fibers, is initiated by mechanical stimulus, and provides targeted pain perception via the spinothalamic tract.
The “slow” pathway is mediated by unmyelinated C-fibers, which respond to noxious chemical stimuli. C-fiber transmissions are carried through the spinal cord via the paleospinothalamamic pathway, which has a diffuse termination in the brain, resulting in poor pain localization.
Referred pain occurs when nerve fibers from different locations in the body synapse with second-order neurons in the spinal canal, creating a diffuse, less localized pain pattern.
The unmyelinated C fibers also release a neurotransmitter called substance P, which promotes nociception and vascular changes. It can lead to vasodilation, which releases more proinflammatory cytokines, creating more C fiber stimulation. Substance P also can create vasoconstriction, which leads to localized ischemia and an increase in diffuse, poorly localized pain – as in trigger points.
Clinical Tip: Radial pressure waves (shockwave therapy) have been shown to decrease the concentration of substance P, which accounts for one of its proposed mechanisms of action for pain control.
Clinical Assessment
The clinical assessment starts with a history and consultation. Is the pain along a nerve distribution (either nerve root or peripheral nerve), neurogenic (burning, sharp) or musculoskeletal (diffuse and achy)? If the pain radiates below the elbow and into the hand, consider it stemming from the cervical spine.
Yet, neck pain alone may be referred proximally from the shoulder. If resting the hand of the affected arm on the top of the head offers relief (Bakody’s sign), look to the spine as the cause. If wearing a sling or immobilization of the shoulder provides relief, consider a shoulder pathology.
Beyond the history and consultation, a thorough examination is required. Remember the basics of motor innervation and manually test muscles related to specific nerve roots: deltoid (C5), biceps (C6), triceps (C7), abductor pollicis brevis (C8), and dorsal interossei (T1).
Combine that with pinprick sensation along each dermatome to isolate cervical nerve root involvement: lateral shoulder (C5), thumb (C6), index finger (C7), small finger (C8). Also check the individual peripheral nerves. Finally, test deep tendon reflexes for symmetry: biceps (C5), brachioradialis (C6), and triceps (C7).
The Arm Squeeze Test
The arm squeeze test has been proposed as another effective differential test for neck / shoulder / arm pain. Since the musculocutaneous (C5-7), median (C5-T1), radial (C5-T1), and ulnar (C7-T1) nerves are superficial in the upper arm, moderate squeezing of the upper arm will create tension on these nerves.
Pain that increases by three points on a VAS scale when the arm is squeezed is diagnostic of cervical pathology; but not when the pain comes from shoulder pathology.
Clinical Tip: Symptoms that include the entire hand, especially sensation, indicate the lesion is in the brachial plexus. When sensory changes are found in multiple peripheral nerves, the lesion is between the shoulder and the neck.
More Testing / Treatment Options
Beyond manual muscle testing related to specific nerve roots, all of the rotator-cuff and shoulder muscles need to be manually tested individually for tendinopathy. Tendinopathy can stimulate slow-acting C fibers and create pain referral from the neck to the upper arm – that dull ache in the shoulder that awakens our patients in the middle of the night.
When testing the rotator-cuff muscles for integrity, be sure to identify if they are weak (neural compression), painful (tendinopathy) or both, Remember, peripheral nerve entrapment can also create motor weakness.
Double crush syndrome, compression along a peripheral nerve at multiple points, can also occur in any of these nerves. Beyond EMG/NCV testing and failure to respond to surgical decompression at a single site, the diagnosis involves palpation of the peripheral nerves along their path, assessing for sites that reproduce symptoms.
Nerve tension signs as described by Shacklock are an excellent diagnostic assessment, too. Unfortunately, it is difficult to determine the percentage of pain to each compression site. Treatment includes nerve gliding techniques and myofascial release of entrapment sites.
Common shoulder conditions include rotator-cuff tendinopathy / tears, adhesive capsulitis, glenohumeral or acromioclavicular arthritis, and subacromial impingement syndrome (SIS). Assessing passive and active ROM is coupled with orthopedic testing to differentially diagnose these conditions. SIS has been shown to be related to poor scapular control and increased thoracic kyphosis.
Clinical Tip: The scapulothoracic articulation is considered part of the shoulder girdle. Although not an osseous joint, it can still be adjusted with various techniques that ensure the scapula is gliding freely in all three planes on the thorax.
Beyond the chiropractic nerve connection, research validates the chiropractic mechanical connection, too. According to Katsuura, “Spinal malalignment specifically in the thoracic region seems to negatively impact the shoulder.” He mentions that “an increased thoracic kyphosis increases anterior tilt and retraction of the scapula ... leading to an increased propensity of subacromial impingement as well as loss of strength in abduction.”
In addition to CMT of the spine and shoulder, strengthening the mid- and lower trapezius, and lengthening the upper trapezius and levator scapulae, are the keys to addressing both the increased kyphosis and anterior tilt of the scapula.
Take-Home Points
Neck, shoulder and arm pain can be multifactorial in nature. The differential diagnosis may be as easy as the arm squeeze test, or it may be more complicated.
Treatment involves addressing the neural and alignment issues discussed above with a multimodal chiropractic paradigm. Decrease the inflammation, restore the length-tension relationships of the involved muscles, and adjust the dysfunctional joints from the neck to the fingers to fix neck / shoulder / arm pain.
Resources
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