Tetraplegia

Tetraplegia, also known as quadriplegia, is defined as the dysfunction or loss of motor and/or sensory function in the cervical area of the spinal cord. A loss of motor function can present as either weakness or paralysis leading to partial or total loss of function in the arms, legs, trunk, and pelvis. (Paraplegia is similar but affects the thoracic, lumbar, and sacral segments of the spinal cord and arm function is retained.) The paralysis may be flaccid or spastic. A loss of sensory function can present as an impairment or complete inability to sense light touch, pressure, heat, pinprick/pain, and proprioception. In these types of spinal cord injury, it is common to have a loss of both sensation and motor control.

Although the most obvious symptom is impairment of the limbs, functioning is also impaired in the trunk and pelvic organs. This can lead to loss or impairment of controlling bowel and bladder, sexual function, digestion, breathing and other autonomic functions. Furthermore, sensation is usually impaired in affected areas. This may manifest as numbness, reduced sensation or neuropathic pain. Secondarily, because of their depressed functioning and immobility, tetraplegics are often more vulnerable to pressure sores, osteoporosis and fractures, frozen joints, spasticity, respiratory complications, infections, autonomic dysreflexia, deep vein thrombosis, and cardiovascular disease.

The severity of the condition depends on both the level at which the spinal cord is injured and the extent of the injury. An individual with an injury at C1 (the highest cervical vertebra, at the base of the skull) will probably lose function from the neck down and be ventilator-dependent. An individual with a C7 injury may lose function from the chest down but still retain use of the arms and much of the hands. An individual in between, with a C5 injury may lose some function from the chest down and fine motor skills in their hands but still have flexion and extension abilities of certain muscles around the back or arm area.

The extent of the injury is also important. A complete severing of the spinal cord will result in complete loss of function from that vertebra down. A partial severing or even bruising of the spinal cord results in varying degrees of mixed function and paralysis. A common misconception with tetraplegia is that the victim cannot move legs, arms, or any other major body regions; this is often not the case. Some tetraplegics can walk and use their hands, as though they did not have a spinal cord injury, while others may use wheelchairs and retain some functions in their arms and fingers; again, this varies based on the degree of damage to the spinal cord and is mostly seen with incomplete tetraplegia.

It is common to have partial movement in limbs, such as the ability to move the arms but not the hands, or to be able to use the fingers but not to the same extent as before the injury. Furthermore, the deficit in the limbs may not be the same on both sides of the body; either side may be more affected, depending on the location of the lesion on the spinal cord.

Another important factor is the possibility that the patient may exhibit sporadic movement in the affected areas. One of the main causes for this would be myoclonus, or muscle spasms. "After a spinal cord injury, the normal flow of signals is disrupted, and the message does not reach the brain. Instead, the signals are sent back to the motor cells in the spinal cord and cause a reflex muscle spasm. This can result in a twitch, jerk or stiffening of the muscle."

Tetraplegia is caused by damage to the brain or the spinal cord at a high level. The injury, which is known as a lesion, causes the loss of partial or total function of all four limbs, meaning the arms and the legs. Typical causes of this damage are trauma (such as a traffic collision, diving into shallow water, a fall, a sports injury), disease (such as transverse myelitis, Guillain–Barré syndrome, multiple sclerosis, or polio), or congenital disorders (such as muscular dystrophy).

Tetraplegia is defined in many ways; C1–C4 usually affects arm movement more so than a C5–C7 injury; however, all tetraplegics have or have had some kind of finger dysfunction. So, it is not uncommon to have a tetraplegic with fully functional arms but no nervous control of their fingers and thumbs. It is possible to have a broken neck without becoming tetraplegic if the vertebrae are fractured or dislocated but the spinal cord is not damaged. Conversely, it is possible to injure the spinal cord without breaking the spine, for example when a ruptured disc or bone spur on the vertebra protrudes into the spinal column.