A spinal cord injury (SCI) occurs when damage to the spinal cord disrupts the flow of nerve signals between the brain and the body. The severity and location of the injury determine the extent of functional loss. An injury at the C6 level—the sixth cervical segment—is generally classified as tetraplegia, meaning it affects all four limbs, the trunk, and the pelvic organs. This injury often leaves significant, though limited, muscle function in the shoulders and arms. This retained function provides a foundation for regaining a substantial degree of independence.
Key Muscles and Movements Preserved
The C5 nerve root, which controls the biceps and the deltoid, is typically spared, allowing for strong elbow flexion and shoulder movement. The defining movement of the C6 level is the preservation of wrist extension, controlled by the extensor carpi radialis longus and brevis muscles. This ability to actively bend the wrist back is the most important factor for functional independence at this injury level.
While individuals with a C6 injury can extend their wrist, they commonly have little to no active control over their hand and fingers. The muscles that control the small, fine movements of the hands are innervated by lower spinal segments, which are affected by the C6 injury. This lack of finger movement makes grasping and pinching objects difficult or impossible without assistance.
The preserved wrist extension, however, allows for a compensatory movement known as the tenodesis grip. This mechanism relies on the natural passive movement of the finger tendons, which cross both the wrist and finger joints. When the wrist is actively extended, the tendons on the palm side of the hand are pulled tight, causing the fingers and thumb to passively curl inward and form a crude grip. Conversely, when the wrist is flexed forward, the finger tendons relax, allowing the fingers to open and release the object. The tenodesis grip is a mechanical advantage that allows individuals to manipulate objects like pens, forks, and cups with adaptive equipment.
Independence in Daily Activities
A person with a C6 injury can often propel a manual wheelchair, particularly over smooth surfaces and for short distances. This is achieved using the preserved strength in the shoulders, biceps, and wrist extensors, sometimes aided by friction hand rims for better grip. Many individuals also choose a power wheelchair for longer distances or uneven terrain to conserve energy.
Transfers, such as moving from a wheelchair to a bed, toilet, or car seat, can often be performed independently using a sliding board. This technique relies on the person’s upper body strength and the ability to stabilize the arms and shift weight.
Self-care tasks become achievable with the aid of adaptive equipment, which leverages the tenodesis grip and preserved arm movement:
- Feeding is typically independent using specialized cutlery or universal cuffs that strap utensils to the hand.
- Grooming activities like brushing teeth, shaving, and hair care are also possible with adaptive devices.
- Dressing the upper body can often be performed with minimal or moderate assistance, while lower body dressing and bowel/bladder management typically require more support or specialized techniques.
- Technology access is an area of high independence; individuals can use computers, phones, and environmental control systems through modified keyboards, mouth sticks, or tools manipulated by the wrist. Furthermore, driving a vehicle is often possible using specialized hand controls after professional evaluation and training.
Common Secondary Health Considerations
A major concern is Autonomic Dysreflexia (AD), a condition affecting individuals with injuries at or above the T6 level. AD is an exaggerated increase in blood pressure triggered by an uncomfortable stimulus below the injury level. Common triggers include bladder distension or bowel impaction. Symptoms often include a pounding headache, facial flushing, and profuse sweating above the level of injury, while the skin below may be pale and cool. If left untreated, the severe hypertension caused by AD can lead to complications such as stroke or seizure.
Respiratory function is also affected due to the loss of control over the intercostal and abdominal muscles. While the diaphragm is innervated by C3-C5, weakness in the chest and core muscles reduces the ability to breathe deeply and cough forcefully. This diminished cough strength can lead to difficulty clearing secretions, increasing the risk of respiratory infections like pneumonia.
Thermoregulation is impaired because the injury disrupts the sympathetic nervous system’s control over sweating and blood vessel constriction below the injury. The body may struggle to cool itself in warm environments or retain heat in cold environments, increasing the risk of hyperthermia or hypothermia. Individuals may experience excessive sweating above the injury level but minimal or no sweating below it.
Chronic neuropathic pain is a common reality, affecting a majority of individuals with a chronic SCI. This pain is caused by damage or dysfunction in the nervous system itself, manifesting as sensations of burning, tingling, electric-shock, or sharp pain. It can occur at the level of injury, where nerve roots may be compressed, or below the level of injury.