Spinal cord injury is defined as Damage to the spinal cord that causes changes in its function, either temporary or permanent. This may cause loss of muscle function, sensation, or autonomic function in parts of the body supplied by the spinal cord below the level of the lesion.
It can be classified as

1) Complete Injury: total loss of sensation and muscle function.
2) Incomplete: some nervous signals are able to travel past the injured area of the cord.

The symptoms can vary from pain or numbness to paralysis to incontinence. The prognosis also ranges widely, from full recovery in rare cases to permanent tetraplegia in injuries at the level of the neck, and paraplegia in lower injuries.
Complications that can occur in the short and long term after injury include muscle atrophy, pressure sores, infections, and respiratory problems.
Reason for injury can be car accidents, gunshots, falls, or sports injuries, but it can also result from nontraumatic causes such as infection, insufficient blood flow, and tumors.
The ability to control the limbs after spinal cord injury depends on two factors:

1) The place of the injury along your spinal cord
2) The severity of injury to the spinal cord.

Paralysis from a spinal cord injury may be referred to as:

 Tetraplegia. Also known as quadriplegia, this means your arms, hands, trunk, legs and pelvic organs are all affected by your spinal cord injury.

 Paraplegia. This paralysis affects all or part of the trunk, legs and pelvic organs.
The lowest part of spinal cord that functions normally after injury is referred to as the neurological level of injury. The severity of the injury is often called "the completeness" and is classified as either of the following: Spinal cord injuries of any kind may result in one or more of the following signs and symptoms:
 Loss of movement
 Loss of sensation, including the ability to feel heat, cold and touch
 Loss of bowel or bladder control
 Exaggerated reflex activities or spasms
 Changes in sexual function, sexual sensitivity and fertility
 Pain or an intense stinging sensation caused by damage to the nerve fibers in your spinal cord
 Difficulty breathing, coughing or clearing secretions from your lungs Signs and symptoms
Emergency signs and symptoms of spinal cord injury after an accident may include:
 Extreme back pain or pressure in your neck, head or back
 Weakness, incoordination or paralysis in any part of your body
 Numbness, tingling or loss of sensation in your hands, fingers, feet or toes
 Loss of bladder or bowel control
 Difficulty with balance and walking
 Impaired breathing after injury
 An oddly positioned or twisted neck or back

When to see a doctor
Anyone who experiences significant trauma to his or her head or neck needs immediate medical evaluation for the possibility of a spinal injury. In fact, it's safest to assume that trauma victims have a spinal injury until proven otherwise because:
 A serious spinal injury isn't always immediately obvious. If it isn't recognized, more severe injury may occur.
 Numbness or paralysis may develop immediately or come on gradually as bleeding or swelling occurs in or around the spinal cord.
 The time between injury and treatment can be critical in determining the extent of complications and the amount of recovery.

If you suspect that someone has a back or neck injury:
 Don't move the injured person — permanent paralysis and other serious complications may result
 Call local emergency medical assistance number
 Keep the person still
 Place heavy towels on both sides of the neck or hold the head and neck to prevent them from moving until emergency care arrives
 Provide basic first aid, such as stopping any bleeding and making the person comfortable, without moving the head or neck

Starts with stabilizing the spine and controlling inflammation to prevent further damage (intravenous steroids) . Treatment options may include:
1) Spinal fracture fixation (pedicle screw stabilization)
2) Spinal laminectomy (decompression) and fixation.
3) Spinal corpectomy and stabilization.
4) Percutaneous pedicle screw stabilization.
5) Stem cell therapy.