The spinal cord is situated within the spinal column. It extends down from the brain to the L1−L2 vertebral level, ending in the conus medullaris. Continuing from the end of the spinal cord, in the spinal canal, is the cauda equina (or “horse’s tail”). The spinal cord itself has neurological segmental levels that correspond to the nerve roots that exit the spinal column between each of the vertebrae.
There are 31 pairs of spinal nerve roots: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal. Owing to the difference in length between the spinal column and the spinal cord, the neurological levels do not necessarily correspond to the vertebral segments.

1. Traumatic SCI can result from many different causes – including falls, road traffic injuries, occupational and sports injuries, and violence.
2. Non-traumatic SCI, usually involves an underlying pathology – such as infectious disease, tumor, musculoskeletal disease such as osteoarthritis, and congenital problems.

Symptoms of spinal cord lesion depend on the extent of the injury or non-traumatic cause, but they can include loss of sensory or motor control of the lower limbs, trunk and the upper limbs, as well as loss of autonomic (involuntary) regulation of the body. This can affect breathing, heart rate, blood pressure, temperature control, bowel and bladder control, and sexual function. In general, the higher up the spinal cord the lesion occurs the more extensive the range of impairments will be. Cervical SCI commonly causes sensory and motor loss (paralysis) in the arms, body and legs, a condition called tetraplegia (the alternative term quadriplegia is now less used). Someone with C4 or higher lesions may require a ventilator to breathe because the lesion directly interferes with autonomic control. Thoracic SCI commonly causes sensory and/or motor loss in the trunk and legs, a condition called paraplegia. Lumbar SCI typically causes sensory and motor loss in the hips and legs. All forms of SCI may also result in chronic pain. The extent and severity of sensory, motor and autonomic loss from SCI depends not only on the level of injury to the spinal cord, but also on whether the lesion is “complete” or “incomplete.” According to the International Standards for Neurological Classification of SCI, with the American Spinal Injury Association (ASIA) Impairment Scale (AIS), an SCI is considered complete if there is no sensory and motor function at S4−S5. While some sensory and or motor function is preserved below the level of injury in incomplete SCI, including the lowest sacral segments S4-S5, it is no less serious and can still result in severe impairments