The primary and essential stage in achieving precise diagnosis and differentiation of cervical radiculopathy involves a comprehensive understanding of the distinct characteristics of pain. This encompasses the evaluation of factors such as the onset timing, precise anatomical location, and potential exacerbating elements or triggering movements. Additionally, an exploration of the patient's professional occupation, age, leisure activities, exercise regimens and modalities, any history of trauma, previous joint conditions, as well as considerations of endocrine and vascular aspects is warranted. Cervical radiculopathy of a primary nature may manifest suddenly or gradually. Trauma frequently triggers its acute onset, with "whiplash" being the prevailing consequence of nonfatal car accidents, posing considerable clinical challenges¹⁸⁾. A current theory regarding whiplash suggests that facet joint strain could lead to a range of secondary symptoms¹⁶⁾. In contrast, cervical radiculopathy caused by conditions such as herniated nucleus pulposus and bony spur due to degenerative changes showed a low association with trauma. According to a population-based study conducted in Rochester, Minnesota, by Radhakrishnan et al.¹⁴⁾, only 14.8% of the 561 patients had a history of physical exertion or trauma preceding the onset of symptoms.

The identification of pain location and patterns of radiation can be helpful in formulating a comprehensive differential diagnosis. During the initial days to weeks of acute cervical radiculopathy, pain may localize to the medial border of the scapula or the shoulder, potentially leading to an initial diagnostic consideration of shoulder pathology¹¹⁾. Traditionally, individuals experiencing cervical radiculopathy commonly describe a blend of strength and sensory disruptions that initiate in the neck and extend to the upper extremity. However, the manifestation can vary depending on variations in myotomes and dermatomes. As radicular symptoms progress, they follow the sensory distribution associated with the affected nerve root. In instances where there is heightened involvement of the cervical root, particularly at C4 or C5, patients may solely exhibit shoulder pain, posing an additional layer of complexity to the diagnostic process⁸⁾. Jo et al.¹⁰⁾ revealed that, after successful anterior fusion surgery for cervical disc herniation, a significant portion of patients with persistent shoulder and arm pain showed a herniated disc at the C4-5 level (36.8%) and the C5-6 level (42.1%). This highlights the crucial need to differentiate between cervical radiculopathy and shoulder pathologies, especially when cervical lesions are located at the C4-5 or C5-6 levels. The complexity arises because shoulder pathologies can present clinical features similar to cervical disc herniation, making the diagnostic process challenging. Sivan et al.¹⁷⁾ observed that 63% of individuals diagnosed with subacromial impingement syndrome reported paresthesia and tingling sensations along the radial side of the arm (C5-6), with these symptoms showing improvement after undergoing arthroscopic subacromial decompression acromioplasty.

The recognition of movements and positions that intensify or alleviate pain proves beneficial in guiding both diagnosis and treatment strategies. In the context of primary cervical pathology, heightened pain during activities involving cervical extension suggests facet pathology. Conversely, individuals reporting relief from neck pain while lying supine with the neck extended may indicate a discogenic origin⁸⁾. Patients with cervical radiculopathy may experience increased pain during cervical extension, lateral bending, or rotation toward the symptomatic side, potentially due to foraminal narrowing. On the contrary, relief from radicular symptoms can be achieved by abducting the shoulder and placing the hand behind the head—a maneuver believed to alleviate tension at the nerve root. Shoulder pain, encompassing the scapular region, may arise from cervical lesions like cervical disc herniation and osteophytic spur. Patients commonly express pain in the neck and one arm, indicating limitations in neck movements, particularly in flexion and rotation. Pain intensifies during cervical movements, strongly suggesting cervical lesions if radiating pain extends below the elbow. Given our comprehension of anatomy and nerve root compression, enhancing the accuracy of diagnosing cervical disc herniation can be achieved through a combination of neurological tests. Wainner et al.²⁰⁾ noted a positive likelihood ratio of 6.0 (95% confidence interval [CI], 2.0-18.6) for three out of four positive tests and 30.3 (95% CI, 1.7-538.2) for four positive tests, which encompass the Spurling sign, upper limb traction test, neck distraction test, and involved cervical rotation test. According to the study by Lauder et al.¹²⁾, exclusively examining neurological symptoms such as weakness, numbness, arm and neck pain, or tingling sensation was not effective in identifying cervical radiculopathy. Although numbness exhibited the highest sensitivity at 79%, its odds ratio was only 1.29 (95% CI, 0.65-2.57). They suggested that the combination of reduced reflexes and comprehensive physical examination findings demonstrated high specificities for diagnosing cervical radiculopathies. The presence of weakness or reflex abnormalities was associated with a fourfold higher likelihood of the subject having cervical radiculopathy. If both weakness and reduced reflex were concurrently present, the likelihood of the subject having cervical radiculopathy increased ninefold.

Shoulder pain is a common complaint encountered in clinical settings, with a prevalence of up to 16% of musculoskeletal complaints⁴⁾. The complexity of the shoulder's anatomy, which includes several joints (acromioclavicular, sternoclavicular, glenohumeral, and scapulothoracic) and dynamic stabilizers like the rotator cuff muscles, makes it susceptible to various pathologies. Differential diagnosis can be challenging due to the overlapping symptoms of cervical and shoulder disorders, which may even coexist. The shoulder’s vulnerability is due to its wide range of motion (ROM) and the anatomical configuration, where the large, spherical head of the humerus interacts with a relatively shallow glenoid. This provides great mobility but compromises stability, relying on both dynamic (muscles) and static (ligaments and labrum) stabilizers. Clinicians should be mindful of common musculoskeletal disorders mimicking cervical radiculopathy, such as rotator cuff pathologies, adhesive capsulitis, and bicipital tendinitis, which can present similarly to cervical issues⁶⁾. Successful treatment depends on an accurate diagnosis, often involving a detailed history, clinical examination, and imaging techniques. In cases where imaging is inconclusive, electrodiagnostic studies and selective injections can be beneficial in identifying the exact pathology.

A thorough clinical history is crucial in differentiating between shoulder and cervical pathology. It should begin with understanding the patient’s demographics, including age, sex, occupation, and hand dominance. Specific attention should be given to comorbidities like diabetes or thyroid disease, which are associated with conditions like adhesive capsulitis. Diabetes, for instance, has been shown to increase the risk of developing adhesive capsulitis due to altered collagen production and microvascular complications, while thyroid dysfunction has been linked to impaired connective tissue metabolism, which can affect shoulder mobility. Patients should be asked about onset, duration, and quality of pain. For instance, pain described as dull or aching is more suggestive of shoulder pathology, while burning or electric-like pain often points to a cervical origin. Activities that exacerbate or alleviate symptoms are also indicative; shoulder pain typically worsens with overhead activities, while cervical pain may be relieved by neck traction or shoulder abduction⁷⁾.

The history should also include any history of trauma, as acute injuries can lead to labral tears or glenohumeral instability, whereas insidious onset is more typical of degenerative or overuse conditions. Athletes who perform repetitive overhead motions or individuals with occupational shoulder strain are particularly prone to specific injuries such as rotator cuff tendinitis or labral tears⁸⁾. A detailed understanding of the aggravating and relieving factors and how the symptoms affect daily activities can provide further clues to the underlying pathology. For instance, shoulder pain that worsens with overhead activities might suggest impingement or rotator cuff involvement, whereas pain relieved by arm support could indicate instability. Understanding these patterns helps clinicians make more targeted decisions regarding further testing and management. Identifying specific activities that worsen or alleviate symptoms helps to determine the structure involved and tailor the treatment accordingly.

The rotator cuff comprises muscles such as the supraspinatus, infraspinatus, subscapularis, and teres minor, which envelop the shoulder joint and contribute to both the stability and movement of the joint. Rotator cuff pathologies are the primary cause of shoulder pain, which includes subacromial impingement syndrome, partial- or full-thickness tears of the rotator cuff, and rotator cuff tendinopathy. Recent pathophysiology explains diseases as being caused by internal factors, external factors, or a combination of both. Internal factors refer to pathological conditions resulting from internal changes such as damage due to excessive traction, ischemia, and degenerative alterations due to aging. External factors indicate conditions caused by external factors such as subacromial impingement and internal impingement. Subacromial impingement, aligned with overuse, involves increased anatomical pressure within the subacromial space due to factors like subacromial spur, acromial shape, and acromioclavicular joint spur, leading to tendon compression in the subacromial space. This corresponds to the classical concept of impingement syndrome, involving biomechanical abnormalities in the coracoacromial arch space, including increased pressure.

Adhesive capsulitis, commonly referred to as "frozen shoulder," is a condition characterized by pain and progressive stiffness of the shoulder joint. Adhesive capsulitis is often considered a symptom rather than a distinct disease, as it frequently occurs in association with underlying conditions. Therefore, identifying and managing any underlying disease, such as diabetes mellitus or thyroid disorders, is crucial. Diabetes mellitus is associated with an increased risk of adhesive capsulitis, potentially due to chronic inflammation and glycosylation of collagen, which affects the shoulder capsule. Similarly, thyroid disorders, particularly hypothyroidism, are thought to contribute to the development of adhesive capsulitis through alterations in metabolic and connective tissue processes⁸⁾.

Calcific tendinitis is a common cause of shoulder pain, characterized by the deposition of calcium hydroxyapatite crystals in the tendons (Fig. 4A, B)¹⁾, most frequently in the rotator cuff, specifically the supraspinatus and infraspinatus tendons. The condition often affects individuals between the ages of 40 and 60, with a prevalence rate of approximately 7% among patients with shoulder pain. It is more common in females and slightly more prevalent in the dominant shoulder. The exact pathophysiology of calcific tendinitis is not fully understood. Unlike degenerative changes typically seen in other tendon pathologies, calcific tendinitis is thought to arise from cellular processes within healthy tendons. This distinction may help explain why the condition occurs at a similar or slightly earlier age compared to degenerative rotator cuff disease. Clinically, calcium begins to deposit within the tendon in a chalk-like form during the formative phase, progresses to a more distinct focus of calcification in the resting phase, and then softens to a toothpaste-like consistency during the resorptive phase. These phases help to explain the variability in symptoms, which can range from asymptomatic to severe, debilitating pain¹⁵⁾.

Suprascapular nerve entrapment is an uncommon but significant cause of shoulder pain and dysfunction, often presenting with symptoms such as weakness and atrophy of the supraspinatus and infraspinatus muscles. The suprascapular nerve (Fig. 5)²⁾, which originates from the brachial plexus, branches from the upper trunk of the brachial plexus (C5 and C6 roots), innervates the supraspinatus and infraspinatus muscles, as well as providing sensory innervation to the shoulder joint and surrounding structures passes through the suprascapular notch—a small depression on the superior border of the scapula near the base of the coracoid process. It is particularly vulnerable to compression or entrapment at this site, leading to suprascapular neuropathy. The nerve can also be compressed at the spinoglenoid notch. Common etiologies include traction injuries related to rotator cuff tears, direct compression from a transverse scapular ligament, or cystic formations at the spinoglenoid notch. This condition is particularly seen in overhead athletes or individuals with repetitive shoulder movements, making early recognition and management critical to preventing chronic dysfunction.

Patients with suprascapular nerve entrapment typically present with poorly localized, dull shoulder pain, which can progress to muscle weakness, especially in shoulder abduction and external rotation. Chronic cases may demonstrate visible atrophy of the supraspinatus or infraspinatus muscles, depending on the site of compression. Diagnosis is based on clinical evaluation, imaging, and electrodiagnostic studies. Magnetic resonance imaging can be particularly helpful in identifying space-occupying lesions such as ganglion cysts, while electromyography can help assess nerve conduction abnormalities.

Initial management of suprascapular nerve entrapment is usually conservative, including physical therapy focused on periscapular strengthening and pain management with nonsteroidal anti-inflammatory drugs. Ultrasound-guided needle aspiration may be employed for cystic lesions, and surgical decompression is considered when conservative measures fail. Both open and arthroscopic surgical options are available to release the transverse scapular ligament or remove cystic compressions, with good outcomes reported for restoring function and reducing pain in patients with persistent symptoms.