Understanding Spinal Cord Injury and Functional Goals & Outcomes

Anatomy and Physiology
The spinal cord is the largest nerve in the body. Nerves are cord-like structures made up of nerve fibers. Nerve fibers are responsible for the communication systems of the body, which include sensory, motor, and autonomic functions. The nerve fibers within the spinal cord carry messages between the brain and the rest of the body. Because the spinal cord is such an important part of the nervous system, protective bone segments, called the vertebral column, surround it. [[See Figure A] ]

The nerves that lie within the spinal cord are upper motor neurons (UMNs). They carry the messages back and forth from the brain to the spinal nerves along the spinal tract. The spinal nerves that branch out from the spinal cord to the other parts of the body are lower motor neurons (LMNs). These spinal nerves exit and enter at each vertebral level and communicate with specific areas of the body. The sensory portion of the LMNs carry messages to the brain about sensation from the skin and other body parts and organs. The motor portion of the LMNs send messages from the brain to the various body parts to initiate actions such as muscle movement. [See Figure C]

The vertebral column, or spinal column, is made up of 4 regions. Seven cervical vertebrae protect the eight cervical nerves; twelve thoracic vertebrae protect the twelve thoracic nerves; five lumbar vertebrae protect the five lumbar nerves; five sacral vertebrae, which are fused as one bone, help protect the five sacral nerves. [See Figure B] As the body grows, the vertebral column grows more in length than the spinal cord, which usually ends between the first and second lumbar vertebrae. From this point the lumbar and sacral nerves branch out from the spinal cord and descend inside the spinal column before leaving the vertebral column at their corresponding vertebrae. Because of this fact there is often a discrepancy between the skeletal or bony level of vertebral fracture and the neurological level of spinal cord injury. [See Figure B]

Level of Injury
The neurologic level of injury is determined to be the most caudal (lowest) point on the spinal cord below which there is a decrease or absence of feeling (sensory level) and movement (motor level) on both sides of the body. The physician tests 10 paired groups of index muscles [myotomes] to determine the motor level of the patient. A motor score between 0 - 5 is given based on motor function. A "3" is given for active, full range of movement against gravity. This is the minimal score needed to set functional goals with a specific level of injury. The 28 key sensory points [dermatomes - the nerve roots that receive sensory information from the skin areas] are also examined for sensitivity to pin prick and light touch. This determines the sensory level. The sensory and motor levels need to be evaluated for both the right and left sides of the body. It is not unusual to have a discrepancy between the lowest normal motor level and the lowest normal sensory level.

Another general classification used to refer to a spinal cord injury are the terms tetraplegia or paraplegia. Tetraplegia [formerly called quadriplegia] generally describes the condition of a person classified with a spinal cord injury between C1 and T1. These individuals experience a loss of feeling and/or movement in their head, neck, shoulder, upper chest, arms, hands, and/or fingers. Paraplegia is the term that describes the condition of a person who has been classified with an injury between levels T2 and S5. The body's motor and/or sensory function(s) affected with paraplegia can include the middle of the chest, the stomach, hips, legs and feet, and/or toes.

Other Classifications
Also included in the neurological assessment is the classification of Clinical Syndromes. The syndromes include Central Cord, Brown-Sequard, Anterior Cord, Conus Medullaris, and Cauda Equina Syndrome. A mixed or unclassified syndrome is sometimes present.

A classification used in the evaluation process is the Functional Independence Measure (FIM). The FIM is a method for monitoring and evaluating progress associated with treatment. It measures daily life activities in the areas of self-care, sphincter control, mobility, locomotion, communication and social cognition. Activities such as eating, toileting, and dressing are rated on a scale which measures dependence/independence.

The chart, "Functional Goals for Specific Levels of Complete Injury", shows the muscle and muscle activity tested and what functional goals can be expected for a person with a complete injury at a particular level. Motor and sensory functions improve with lower levels of injury.

The greatest number of injuries occur between the ages of 16 and 30 (55%). The mean age at time of injury has increased from 28.6 in 1979 to 35.1 in 1990.

Since 1990, motor vehicle crashes account for 37.4% of the SCI cases reported. The next largest contributor is acts of violence (25.9%), primarily gunshot wounds. The third most common cause is falls at 21.5%, with sports injuries ranking fourth at 7.1%.

Spinal cord injury can occur at any level of the spinal column or at multiple levels. The most common area of injury is the lower part of the neck at the C-4, C-5, and C-6 levels. The second most common area is between T-12 and L-1, which is at the bottom of the rib cage. Since 1990 the most frequent neurologic category is incomplete tetraplegia (29.5%), followed by complete paraplegia (27.9%), incomplete paraplegia (21.3%), and complete tetraplegia (18.5%).

Individuals with a spinal cord injury designated as having tetraplegia are slightly more common than paraplegia, 51.7% and 46.7%, respectively.