Spinal Cord Injury FAQs

Find comprehensive answers to frequently asked questions received by the Mount Sinai Spinal Cord Injury Program.

What is Spinal Cord Injury?
Spinal cord injury (SCI) is damage to the spinal cord that results in a loss of function such as mobility and/or feeling. The spinal cord does not have to be completely severed or cut for someone to lose functioning.

What are the spinal cord and the vertebrae?
The spinal cord is about 18 inches long and extends from the base of the brain to about the waist. The spinal cord carries nerve impulses to and from the brain to the rest of the body. The spinal cord is surrounded by rings of bone, called vertebrae, which constitute the spinal column. The vertebrae are named according to their location. There are seven cervical vertebrae (neck), twelve thoracic (chest), five lumbar (waist), and five sacral (buttocks) vertebrae.

What is an upper motor neuron (UMN)?
The nerves that lie within the spinal cord are called UMNs, and they carry messages back and forth from the brain to the spinal nerves along the spinal tract. Injury to the upper motor neurons results in a loss of coordinated and integrated control of reflex activity below the level of injury. This can result in spasticity of the limbs, bowel, and bladder.

What is a lower motor neuron (LMN)?
The spinal nerves that branch out from the spinal cord to the other parts of the body are called LMNs. These spinal nerves exit and enter at each vertebral level and communicate with specific areas of the body. The sensory portions of the LMN carry messages about sensation from the skin and other body parts and organs to the brain. The motor portions of the LMN send messages from the brain to the various body parts to initiate actions such as muscle movement. LMN injuries destroy the reflex arc and interrupt communication to the UMN. They result in paralysis of the lower limbs and loss of bowel and bladder function.

What are the effects of SCI?
The effects of SCI depend on the type of injury and the level of the injury. SCI can be divided into two types of injury: complete and incomplete. Different levels of injuries include tetraplegia (quadriplegia) and paraplegia. Cervical SCIs usually cause loss of function in the arms and legs, resulting in tetraplegia. Injuries to the thoracic region usually affect the chest and the legs. Similarly, injuries to the lumbar vertebra and to the sacral vertebrae generally cause some loss of functioning in the hips and legs. Thoracic, lumbar, and sacral injuries result in paraplegia.

What is the difference between a complete and incomplete injury?
A complete injury means that there is no function below the level of the injury: no sensation and no voluntary movement. An incomplete injury means that there is some functioning below the primary level of the injury, including sensation and/or movement.

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