Compression of the C5 or C6 nerve roots in the neck is a very common cause of pain perceived in the shoulder. This phenomenon is known as referred pain, where nerve irritation in the cervical spine transmits pain signals that the brain interprets as originating from a different location, such as the shoulder or arm. Since the nerves that exit the lower neck travel directly into the shoulder and arm, problems in the spinal column often manifest far from the neck itself. Understanding this connection is the first step toward accurately diagnosing and effectively treating the source of shoulder discomfort.
The Anatomical Link Between C5/C6 and Shoulder Sensation
The mechanism behind this referred pain begins with the C5 and C6 spinal nerves, which exit the cervical spine between the C4-C5 and C5-C6 vertebrae, respectively. These two nerve roots are major contributors to the brachial plexus, a complex network of nerves that governs motor and sensory function for the entire upper limb. Once the C5 and C6 roots combine, they form the superior trunk of the brachial plexus, which is responsible for innervating many of the muscles that move the shoulder and elbow.
The C5 nerve root primarily supplies the deltoid muscle, responsible for shoulder abduction, or lifting the arm away from the body. It also provides sensation to the skin over the outer shoulder and upper arm, an area known as the C5 dermatome. The C6 nerve root contributes heavily to the biceps muscle, controlling elbow flexion, and the wrist extensor muscles.
The sensory distribution of C6, its dermatome, typically runs along the lateral forearm and extends into the thumb and index finger. When the C5 or C6 nerve root is compressed, the pain and other symptoms, such as weakness or tingling, follow these specific pathways.
Specific Spinal Conditions Causing C5/C6 Compression
The compression or irritation of the C5 or C6 nerve root is medically termed cervical radiculopathy. This condition is caused by several specific structural changes within the cervical spine.
One of the most common acute causes is a cervical disc herniation, where the soft, gel-like center of the intervertebral disc pushes outward. If this material presses on the nerve root as it exits the spinal canal, it generates immediate symptoms.
Another frequent cause, particularly in older adults, is degenerative disc disease or cervical spondylosis. This involves the natural, age-related wear and tear of the spinal components, leading to the formation of bone spurs, known as osteophytes, along the edges of the vertebrae. These bony growths can narrow the space through which the nerve roots pass, physically pinching the nerve.
Spinal stenosis describes the narrowing of the spinal canal or the neural foramina, the small openings where the nerve roots exit the spine. This narrowing can be caused by disc degeneration, thickened ligaments, or bone spurs, creating the physical impingement necessary to trigger the referred shoulder pain.
Distinguishing C5/C6 Nerve Pain from True Shoulder Joint Issues
Differentiating nerve-related pain originating from the neck from true musculoskeletal pain originating in the shoulder joint, such as a rotator cuff tear or arthritis, is a highly practical step for diagnosis. Pain caused by C5/C6 radiculopathy is often described as sharp, electric, or burning, and it frequently radiates or shoots down the arm into the forearm and hand in a distinct C5 or C6 pattern. True shoulder joint pain, by contrast, is usually a deep, dull ache localized to the shoulder itself, often felt on the side or back of the joint.
The activities that provoke the pain also differ significantly between the two sources. C5/C6 nerve pain is commonly aggravated by specific neck movements, such as tilting the head toward the affected shoulder, which further compresses the nerve root. Conversely, a true shoulder joint problem is typically worsened by shoulder-specific movements, especially lifting the arm overhead or reaching behind the back.
Accompanying symptoms provide further clues, as radiculopathy often includes sensory changes like numbness or tingling, known as paresthesia, along the specific C5 or C6 dermatome. Muscle weakness may also be present, specifically affecting the shoulder abductors (C5) or the elbow flexors and wrist extensors (C6). A primary shoulder joint issue usually does not produce these neurological symptoms.
Medical Diagnosis and Initial Treatment Strategies
A physician begins the diagnostic process with a thorough physical examination to pinpoint the source of the pain. This includes specific provocation tests, such as the Spurling’s maneuver, which involves extending and rotating the neck to the affected side while applying a gentle downward pressure to see if it reproduces the arm pain. The doctor will also check reflexes, muscle strength, and sensation along the C5 and C6 pathways to identify the specific nerve root involved.
While plain X-rays can show the bony structure, revealing disc space narrowing or bone spurs, magnetic resonance imaging (MRI) or a computed tomography (CT) scan are the confirmatory imaging studies. An MRI is particularly useful because it visualizes the soft tissues, allowing the physician to see a disc herniation or nerve root compression directly. These scans help rule out other conditions and confirm the cervical spine as the pain source.
The initial treatment for C5/C6 radiculopathy is overwhelmingly conservative and non-surgical, aiming to reduce inflammation and relieve pressure on the nerve root. Non-steroidal anti-inflammatory drugs (NSAIDs) are commonly used to manage pain and swelling. Physical therapy is a major component of recovery, focusing on postural correction, neck stabilization exercises, and sometimes the use of gentle cervical traction to unload the pressure on the nerve. For persistent pain that does not respond to these conservative measures, a targeted epidural steroid injection may be considered to deliver powerful anti-inflammatory medication directly to the irritated nerve root.