Nontraumatic Spinal Cord Injury

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What is Nontraumatic Spinal Cord Injury?

Nontraumatic Spinal Cord Injury (NTSCI) is any damage to the spinal cord that has not been caused by a major trauma. So rather than the spinal cord being injured in a traumatic impact like a car crash or a fall, it has been damaged in other ways such as infection, loss of blood supply, compression by a cancer or through slow degeneration of the spinal bones (vertebrae) such as in osteoarthritis.

The spinal cord is about 46cm long, and contains many nerve cells that create signals, nerve fibres that transmit the signals as well as other cells that look after the nerve cells. Around the spinal cord are a stack of bones known as the vertebrae that provide support and protection for the delicate nerve cells inside.

The spinal cord acts as a connector between the brain and the body; the brain sends signals out through nerves that run down the spinal cord, and from there other nerves go out into the body. These control things like movement of muscles, but also other functions such as sweating, urination and defecation. The body also sends signals up through the spinal cord to the brain via other nerves giving information about touch, temperature, position and pain.

This delicate cord can be damaged anywhere along its path. The effects of the injury will depend on where in the spinal cord the damage occurred. When the cord is damaged, the nerve cells above that level are usually still okay, but below that level they can no longer communicate with the brain. If the damage is high up then there can be more loss than if the injury was lower in the spinal cord. This means the brain can no longer send or receive information to or from the parts of the body supplied by levels of cord at or below the level of injury, meaning it is unable to control movement or feel any sensations.

In a nontraumatic spinal injury, something has happened that has stopped this connection. There are lots of things that can cause a nontraumatic injury, and many of these are listed below. What are more important however, are the many complications that can arise from an NTSCI, and these are covered under Natural History.

Who gets Nontraumatic Spinal Cord Injury?

The number of nontraumatic spinal cord injuries is difficult to know because there are so many different causes, and there is no one big registry where all the information is kept. While it is thought that in the United States there are between 183 000 and 230 000 people with traumatic spinal cord injuries, it is thought that if you included nontraumatic cases then this number would more than quadruple.

In Australia, the rate is thought to be about the same as overseas, with a rate of nearly 31 injuries for every million people per year; twice that of traumatic injuries.

Predisposing Factors

One of the major factors that predisposes to NTSCI is simply age, the older you are the more likely it is to have an injury of this type. This is because many of the causes (listed below) increase with age. For this reason, as our population ages and a greater percentage of people are in an older age bracket, it is likely that the number of nontraumatic spinal cord injuries will begin to rise.

To understand the factors that can predispose to nontraumatic spinal cord injury, it is important to first understand what the many causes are.

Causes

Causes of NTSCI can be divided into five categories:

Vascular: this makes up about 25% of all NTSCI and these causes are due to things that involve blood and the blood vessels. Examples of this include:

Epidural Haemorrhage: bleeding into the area around the spinal cord can compress the nerves and cause damage
Severe Hypotension: if the heart cannot pump blood well enough, then sometimes the blood pressure can fall so low that not enough blood gets to the spinal cord, causing damage.
Cardiac arrest: can cause the heart to stop pumping blood efficiently, leading to a loss of blood supply to the cord
Atherosclerosis: a build up of fatty plaque in the vessels leading to the cord can block blood supply. This could be thought of as like a 'heart attack' of the spinal cord.
Embolism: a clot can break off from somewhere in the body - usually the heart - and block off the arteries that supply and area of the spinal cord.

Neoplastic (Cancerous): This makes up another 25% of all NTSCI. Around 5% of all cancers can lead to spinal cord compression, either from local cancers in the bone or cord or having spread (metastasised) from another location:

Vertebral cancers can either have spread from another site, or can cause local damage such as with myeloma.
Most cancers that compress the cord are ones that have spread from another site. The most common cancers that spread to the spine are lung, breast, prostate, lymphoma, thyroid or melanoma.
Cancers can also form from the structures inside or surrounding the spinal cord and this can also compress it and cause damage. Examples of these include meningiomas (cancers of the membrane covering the spinal cord) and gliomas (cancers of supporting cells)

Inflammatory and Infections: these account for about 20% of all NTSCI injuries. Damage is from big masses of inflammatory cells or localised areas of infection:

Epidural abscess: a build up of pus and bacteria outside the spinal cord can cause compression and damage
Tuberculosis: TB causes localised areas of inflammation and growth that leads to compression.
Granuloma: a granuloma is a localised area of inflammation that does not go away and can be caused by a condition like Sarcoidosis
Transverse Myelitis: a condition where a previous infection leads to a loss of a protective coating that covers nerve cells. This can lead to poor signal transmission through the nerves.

Degenerative: these conditions are due to general breakdown due to wear and tear or other damaging process occurring to the bones and accounts for about 18% of all NTSCI.