The cervical spine consists of the seven vertebrae in the neck, protecting the central nervous system. Spinal nerves exit the column through small openings, acting as communication pathways between the brain and the body. In the neck, eight pairs of cervical nerve roots (C1 through C8) form the brachial plexus. The C6 and C7 nerve roots exit the lower neck and primarily govern the motor and sensory functions of the arm and hand.
The C6 Nerve Root: Function and Reflexes
The C6 nerve root exits between the C5 and C6 vertebrae and is a frequently affected nerve in the cervical region. Its motor function primarily involves elbow flexion, controlled largely by the biceps, and wrist extension, allowing the hand to be pulled back toward the forearm. Damage to this nerve often results in noticeable weakness when attempting to lift objects or maintain a strong grip.
The sensory component, or dermatome, maps to the lateral side of the forearm, extending into the thumb and the index finger. Irritation commonly causes numbness or a tingling sensation that follows this precise distribution. Clinicians test the associated reflexes, including the brachioradialis reflex and the biceps reflex (which also relies on the C5 root).
The C7 Nerve Root: Function and Reflexes
The C7 nerve root exits between the C6 and C7 vertebrae and is the most common nerve root affected by compression in the neck. Its motor responsibilities focus on movements opposite to C6, providing power for elbow extension via the triceps muscle. It also controls the wrist flexors, which bend the wrist forward, and the extensors of the fingers.
Impairment typically manifests as difficulty with pushing motions, such as pushing a door open or rising from a chair, due to triceps weakness. The C7 dermatome runs down the middle of the back of the arm and forearm, culminating in the middle finger. Irritation commonly causes numbness or paresthesia, often described as a “pins and needles” sensation, localized to the central digit. The triceps reflex is exclusively associated with this nerve root and is tested by tapping the triceps tendon just above the elbow.
Common Causes of C6 and C7 Nerve Impingement
Irritation or compression of a spinal nerve root, medically termed radiculopathy, often stems from structural changes in the cervical spine. A frequent cause of C6 or C7 impingement is a cervical disc herniation, where the soft, inner material of an intervertebral disc pushes through its tougher outer layer. This bulging material can directly press upon the nerve root as it exits the spinal canal, leading to symptoms.
Degenerative Conditions
With advancing age, degenerative processes become a common source of nerve irritation. This includes cervical spondylosis, encompassing degenerative disc disease and the formation of bone spurs, or osteophytes. These bony growths develop as the body attempts to stabilize the worn joints, but they narrow the space available for the nerve roots. Narrowing in the central spinal canal is called spinal stenosis, which can compress the spinal cord or the nerve roots.
Recognizing Symptoms and Clinical Assessment
The subjective symptoms of C6 or C7 radiculopathy are often described as pain, tingling, or numbness that originates in the neck and radiates down the arm and into the hand. This radiating pain is a hallmark sign because its distribution follows the specific dermatome maps of the affected nerve root (e.g., the thumb for C6 or the middle finger for C7). Symptoms may be worsened by neck movements, such as tilting the head toward the affected side, which further compresses the nerve root.
Neurological Examination
A physician assesses C6 and C7 function through a focused neurological examination. This assessment involves testing muscle strength against resistance, specifically evaluating the power of the wrist extensors and biceps for C6, and the triceps and wrist flexors for C7. Deep tendon reflexes are examined, looking for a diminished or absent response in the biceps/brachioradialis (C6) and the triceps (C7). Sensory testing confirms the dermatomal pattern of numbness or altered sensation. A provocative test like the Spurling maneuver may also be used to reproduce the radiating pain and confirm the clinical diagnosis of radiculopathy.