- The majority of spinal cord injuries occur in young males between 25 – 45 years who are at the peak of their productivity.
- 40% of spinal cord injuries in New Zealand are a result of motor vehicle accidents.
- The average cost of care for each high level tetraplegic is NZ$212,000 per year.
- New Zealand has one of the highest rates of SCI in the western world with the associated rehabilitation and hospital costs being among the highest for all injuries.
Five segments of the vertebral column
The spinal column houses the spinal cord and is often referred to as the vertebral column. This vertebrae are classified in five segments as detailed below.
Seven vertebrae make up the cervical spine with eight pairs of cervical nerves. The individual cervical vertebrae are abbreviated C1, C2, C3, C4, C5, C6 and C7.
The Thoracic spine is located in the chest area and contains 12 vertebrae. The ribs connect to the thoracic spine and protect many vital organs. Individual vertebrae are abbreviated to T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11 and T12.
These five bones are the largest vertebrae in the spinal column. These vertebrae support most of the body’s weight and are attached to many of the back muscles. Individual vertebrae are abbreviated to L1, L2, L3, L4, and L5.
The sacrum is a triangular bone located just below the lumbar vertebrae. It consists of four or five sacral vertebrae in a child, which become fused into a single bone in adulthood.
The bottom of the spinal column is called the coccyx. This consists of 3-5 bones that are again fused in an adult.
Spinal cord overview
The spinal cord is part of the nervous system and runs the length of the back, extending from the base of the brain at the medulla to about the waist at the conus medularis. The spinal cord is housed within the spinal column. Within the column, the cord is surrounded by cerebral spinal fluid. This fluid acts as a buffer to protect the spinal cord from damage sustained by striking the inside of the vertebral column.
Spinal cord illustration
The diagram below illustrates the main anatomical features of the spinal cord. The function of the main areas highlighted are listed below.
- Spinal Nerve – Carries nerve impulses
- Dorsal Root Ganglion – Receives impulses from other areas such as the skin for transmission to the brain.
- Central Canal – Fluid filled space running the length of the spinal cord
- Grey Matter – Contains nerve cell bodies.
- White Matter – contains the axons of the spinal cord.
The spinal cord carries out two main functions, and is effectively a superhighway for communication of signals.
Firstly, it connects a large part of the nervous system to the brain. Nerve impulses are transmitted to the spinal cord through sensory neurons. These impulses are then transmitted by the spinal cord to the brain. This pathway is known as the ascending tract of nerves. In the reverse process, impulses are generated in the brain, which are transmitted down the cord and leave by the motor neurons. This pathway is known as the descending tract of nerves.
Secondly, the spinal cord acts as a co-ordinating centre in order to produce simple reflexes such as the withdrawal reflex.
The area within the spinal column beyond the end of the spinal cord is called the cauda equina. The nerves that branch out from the spinal cord to the other parts of the body are called lower motor neurons (LMNs) and dorsal root sensory neurons.
The impact after spinal cord injury depends on the severity of the injury and the location of the spinal cord segments injured.
There are two types of injury which are known as complete and incomplete.
In a complete injury, the spinal cord is damaged across the whole of its width so that there is no function below the level of injury.
In an incomplete injury, the injury does not spread across the whole of the spinal cord; some areas away from the injury remain intact or at least intact enough to retain some function. People with incomplete injuries have some sensation and/or movement control below the level of injury.
The higher the location of the injury in the spinal cord, the greater the proportion of the body affected. Thus, injuries higher up the spinal cord cause relatively greater paralysis and dysfunction than lower spinal injuries: injuries in the cervical region cause paralysis in both the arms and then legs (known as tetraplegia or quadriplegia) whereas injuries in the thoracic region cause paralysis in the legs, which is called paraplegia.