The spinal cord, part of the central nervous system, is the largest nerve in the human body (approximately 50 cms long and 2.5 cms in diameter) comprised of millions of nerve fibres orientated into tracts that relay nerve transmissions up and down the cord from the brain to other parts of the body such as the limbs, trunk and organs. The nerve fibres communicate sensory, motor (movement) and autonomic (involuntary) information for normal control and maintenance of bodily functions. The spinal cord is surrounded by cerebrospinal fluid (CSF) that cushions, bathes and nourishes the cord. The spinal cord itself is contained within the spinal canal formed by the vertebrae of the vertebral column.

The ascending tracts (transmission towards the brain) carry information relating to pain, temperature, touch, and joint position in space as well as information from other body parts and organs. The tracts carrying information relating to pain and temperature are found in the middle of the cord and are known as “spinothalamic tracts”. Ascending tracts carrying information of touch sensation and joint position are located at the back of the cord and known as “dorsal columns”. The descending tracts at the front of the cord carry information to various body parts such as the limbs to initiate and coordinate movement.

The autonomic nerve pathways are divided into two types - sympathetic and parasympathetic. These nerve pathways are extremely important in regulating and maintaining a stable internal “environment” within the body. Both are largely uncontrollable by our conscious control working automatically and antagonistically to balance control mechanisms by increasing or decreasing them. The autonomic system influences the activities of smooth muscles, the heart muscle and hormone secreting glands. Therefore it exerts a control over cardiovascular, respiratory and digestive systems influencing blood pressure, heart rate, sweating and feelings such as anxiety and general irritability.

The spinal cord ends between vertebral level L1-L2 and at this level the cord is known as the conus medullaris; below this extends the cauda equina (horses' tail in Latin) consisting of a number of spinal nerves continuing downwards until exiting between the vertebrae. Information leaves and returns to the spinal cord through spinal nerves which leave the cord and exit through the foramina (openings) found between the vertebrae of the vertebral column. There are 31 bilaterally paired spinal nerves, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal. They are numbered in “neurological” sections for reference as C1-C8, T1-T12, L1-L5, and S1-S5 respectively.

The vertebral column (spine) consists of a series of 33 individual bones called vertebrae. The vertebral column is divided into anatomical sections with each vertebra being numbered for reference - cervical (7 vertebra numbered C1-C7), thoracic (12; T1-T12), lumber (5; L1-L5), sacrum (5; S1-S5, fused during late teens/early twenties) and coccyx (4 fused). The spinal anatomy is a remarkable structure consisting of very strong bones, pliable ligaments and tendons, large associated muscles plus associated nerves that afford protection for the spinal cord and spinal nerve roots whilst allowing a high degree of mobility around many planes.

The vertebral segments do not completely coincide with the “neurological” segments because during growth the vertebral column grows longer in length than the spinal cord; there are 7 cervical vertebrae and 8 cervical spinal nerves; the thoracic spinal cord segments (T1-T12) are compressed between T1 and T8 vertebrae, the lumbar spinal cord segments (L1-L5) exist between T9 and T11 vertebrae and sacral spinal cord segments (S1-S5) are located between T12 to L1/L2 vertebrae. Therefore the higher the vertebral injury level the greater the level of neurological dysfunction.