Spinal Cord Injury Explained: Levels, Completeness and the Data

Spinal cord injury explained: levels, completeness, and why most injuries are not what people picture

Ask somebody to picture a spinal cord injury and they will describe a complete one. A clean break. Everything working above the line, nothing working below it.

The Australian data says otherwise. In the most recent Australian Institute of Health and Welfare report from the Australian Spinal Cord Injury Register, covering 2017–18, of 161 persisting traumatic injuries where completeness was recorded at discharge, 112 were incomplete and 49 were complete. Among cervical injuries — the ones that produce tetraplegia, the injuries people picture most vividly — 77.5 per cent were incomplete.

That matters for reasons well beyond accuracy. An incomplete injury means some signal still crosses the damaged segment. It means the picture is messier: patchy sensation, a leg that works better than the other, movement that is present but not useful, bladder function that is unpredictable rather than absent. It means two people with the same injury level can have entirely different function. And it means the generic assumptions — about what somebody can feel, what they can do, what they will need — are wrong more often than they are right.

It also means the single most common mistake in this field is treating the injury level as the whole answer. The level tells you where. Completeness tells you how much. You need both, and even then you need the person.

We support NDIS participants with spinal cord injury across New South Wales. We are not a spinal unit, we do not provide medical care, and nothing in this guide is medical advice. What we can set out is how the classification works, what the Australian numbers actually show, and what the terminology means when it appears in a discharge summary or an NDIS report — because people are handed these documents and left to decode them.

The anatomy, briefly, because the rest depends on it

The spinal cord runs from the base of the brain down through the bony canal of the spine. It is not a single cable but a bundle of tracts carrying different kinds of information in different directions — motor signals down, sensory signals up, and autonomic signals that control blood pressure, bladder, bowel, temperature and sexual function.

The cord is shorter than the spine it sits in. It ends around the first or second lumbar vertebra, below which the canal contains a bundle of nerve roots called the cauda equina. This is why a fracture at a particular vertebral level does not necessarily produce injury at the matching cord level, and why lower injuries sometimes damage nerve roots rather than cord — which behaves differently and matters clinically.

Nerves exit the cord in pairs at each segment, and each segment supplies a predictable region of skin and a predictable group of muscles. That predictability is the whole basis of the classification.

The segments, grouped:

Two terms worth getting right because they are used inconsistently. Tetraplegia and quadriplegia mean the same thing — a cervical injury affecting all four limbs. Tetraplegia is the term now preferred clinically; quadriplegia still appears in older records and in legislation, including on the NDIS access lists. Paraplegia means injury below the cervical segments, with the arms unaffected.

How the classification actually works

The international standard is the ISNCSCI — the International Standards for Neurological Classification of Spinal Cord Injury — which produces what most people know as the ASIA classification, after the American Spinal Injury Association.

The examination tests two things systematically, on both sides of the body:

Motor — the strength of a key muscle group for each of ten segments, graded 0 to 5. Zero is no contraction. Five is normal strength against full resistance. Three is the pivotal grade: movement against gravity but not against resistance, which is often the difference between a movement being present and being useful.

Sensory — light touch and pin prick at a specific point for each of 28 segments on each side, graded absent, altered or normal.

From that examination you get:

The neurological level of injury — the lowest segment with normal motor and sensory function on both sides. This is frequently different from the vertebral level named in the surgical notes, which is a common source of confusion.

The motor and sensory levels, which can differ from each other and between sides.

Whether sacral segments are spared — tested by sensation around the anus and voluntary anal contraction. This single finding largely determines the completeness grade, which is why an examination that skips it is incomplete.

The AIS grade — the headline letter:

• AIS A — complete. No motor or sensory function in the lowest sacral segments.
• AIS B — sensory incomplete. Some sensation below the level including the lowest sacral segments, but no motor function more than three levels below.
• AIS C — motor incomplete. Motor function preserved below the level, but more than half the key muscles below it are weaker than grade 3.
• AIS D — motor incomplete. At least half the key muscles below the level are grade 3 or better.
• AIS E — normal on examination, in somebody who had deficits previously.

The practical significance of that scale is enormous and routinely underappreciated. The gap between AIS C and AIS D is the gap between movement that exists and movement you can use. The gap between AIS A and AIS B is the gap between no information from the body below the injury and some — which affects pain, pressure injury risk, sexual function and how a person experiences their own body.

Two cautions about the grade. First, it is unreliable in the first days after injury, when spinal shock can mask preserved function; a grade recorded on day two is not a prognosis. Second, it describes the examination, not the person. Two people graded AIS C at C6 can have completely different lives.

The syndromes, which explain the odd presentations

Some incomplete injuries damage specific parts of the cord cross-section and produce recognisable patterns. These are worth knowing because they explain presentations that otherwise look inexplicable.

Central cord syndrome. The most common incomplete pattern, typically from a hyperextension injury in a neck with pre-existing degenerative narrowing — which is why it is common in older people after relatively minor falls. Arms are affected more than legs, and hands more than shoulders. The person may walk into a clinic unable to use their hands, which is the opposite of what people expect.

Brown-Séquard syndrome. Damage to one side of the cord. Weakness on the injured side, loss of pain and temperature sensation on the opposite side. Confusing to live with and to explain.

Anterior cord syndrome. Loss of motor function and pain and temperature sensation, with position sense and vibration preserved. Generally a poorer prognosis for motor recovery.

Cauda equina syndrome. Damage to the nerve root bundle below the cord itself. Produces leg weakness, saddle anaesthesia and bladder and bowel dysfunction. It is a surgical emergency, and because it involves nerve roots rather than cord, the recovery profile differs.

Conus medullaris syndrome. Injury at the very end of the cord, with a mixed picture of cord and nerve root features.

The Australian numbers, and what they say about who this happens to

From the AIHW’s 2017–18 Australian Spinal Cord Injury Register report:

New cases. 187 traumatic spinal cord injuries in people aged 15 and over, of which 176 were persisting. Separately, 131 non-traumatic cases were admitted to participating spinal units, and 13 cases arose as complications of medical care.

The register notes a caveat worth repeating: 2017–18 registrations were about 18 per cent lower than the previous year’s 230, and the drop was not fully explained. Single-year figures from this register should be read with that in mind.

Incidence rate. The age-standardised rate of persisting traumatic injury was 8.6 per million population in 2017–18, down from 11.1 the year before. The three-year rate across 2015–16 to 2017–18 was 10.6 per million. The long-run trend is a decline of roughly 2.5 per cent a year since 1995–96, which is a genuine public health achievement attributable largely to road safety.

Where it happens. This is the finding that should get more attention than it does. Across the three-year period, the rate in remote Australia was 25.8 per million against 8.6 in major cities — three times higher. By jurisdiction, Western Australia was highest at 14.6 and the ACT lowest at 5.9. Rural and remote Australians are injured more and then live further from the spinal units, specialist clinics and equipment services that the rest of this library assumes access to.

Who. Of the 176 persisting traumatic injuries, 140 were male and 36 female — 80 per cent male, with male rates higher in every single age group. The age distribution has two peaks: the largest group was 25 to 34 (37 cases, 21 per cent), followed by 55 to 64 (32 cases, 18 per cent). Age-specific rates were actually highest at 55 to 64 (11.2 per million) and then 65 to 74 (10.1).

That second peak is the important one, and it is growing. It is largely older people having low falls.

How.

Three things stand out.

Unprotected road users are the single largest cause — motorcyclists, cyclists, quad bike riders and pedestrians, at 29 per cent of all cases and 33 per cent of male cases.

Low falls were concentrated in people aged 65 and over. A fall of less than a metre, in an older neck with existing degenerative change, is a mechanism for central cord syndrome. This is the demographic shift in spinal cord injury that the service system has not caught up with, and it collides directly with the NDIS age limit of 65.

All 14 water-related injuries were cervical. Every one. Diving and surfing were the main activities, and 86 per cent were male. There is no such thing as a mild diving injury to the neck; the mechanism delivers an axial load to a flexed cervical spine and the result is tetraplegia. If there is one piece of prevention messaging in this guide, it is that.

Activity at the time of injury: 43 cases (23 per cent) were in sport or leisure, almost all male; 20 cases (11 per cent) were working for income.

Level and completeness at discharge, for 161 persisting cases with known level:

Cervical injuries are the majority. Incomplete injuries are the majority. And completeness varies sharply by level — cervical injuries are far more likely to be incomplete than thoracic ones.

How many Australians are living with this

Incidence is small. Prevalence is not, because people live for decades.

A 2020 report prepared by AlphaBeta for SpinalCure Australia estimated that around 20,800 Australians were living with spinal cord injury, excluding children under 15, with about 380 new incidences expected that year.

Its other findings:

• 42 per cent have tetraplegia, 58 per cent paraplegia.
• About a third — 6,910 people — have a severe injury, graded AIS A or B.
• Almost 23 per cent are under 35, and most are under 65.
• Around 70 per cent of new incidences are in men.
• For people under 65, over 80 per cent of injuries are traumatic. Above 65, non-traumatic causes lead — tumours, degenerative conditions, vascular events, infections.

That last split is worth holding onto, because non-traumatic spinal cord injury is substantially under-discussed. It does not come with a crash, a compensation scheme or a news story. It often comes with a slow diagnosis and no spinal unit admission at all, and the person ends up with the same functional consequences and considerably less support.

The number that should reframe the whole conversation

The same report costed spinal cord injury in Australia at approximately $74.5 billion in total lifetime cost, or around $3.7 billion a year.

Here is how that breaks down:

Personal care is nearly ten times the health care cost.

And the health care trajectory makes the point sharper. The report estimated health care costs of roughly $52,000 to $82,000 in the year of injury — and then about $5,000 to $10,000 a year from year seven onwards.

So spinal cord injury is expensive at the start and then medically inexpensive for the following forty years. What it is for those forty years is support-intensive. The cost is somebody helping with a bowel programme, a transfer, a shower, a catheter, getting to work.

That reframing matters because it tells you where the harm concentrates when the system underfunds. Nobody in Australia is denied the acute surgery. What gets rationed is the hours.

Lifetime cost per person, from the same report:

Severe tetraplegia costs up to 148 per cent more than AIS D tetraplegia. Which is another way of saying that completeness, not just level, drives everything.

Informal care carried an opportunity cost of $5.6 billion, and up to 70 per cent of people with spinal cord injury have an informal carer — usually a family member, usually unpaid, frequently in place because the funded hours do not cover the need.

What else comes with it

Spinal cord injury is not only about movement, and the secondary consequences are where most of the long-term harm sits. From the AlphaBeta report:

• Bladder or bowel control loss affects 80 per cent of people with spinal cord injury, and is identified as the leading cause of rehospitalisation due to infection.
• Chronic pain lasting more than six months affects 70 per cent, with about a third reporting severe pain.
• Respiratory failure affects 70 per cent of people hospitalised with spinal cord injury.
• PTSD affects up to 40 per cent after traumatic injury, and up to 30 per cent are at risk of depression.

Each of those has its own guide in this library, because each is routinely under-treated. The pain figure in particular deserves attention: 70 per cent with chronic pain and a third of those severe, in a population whose pain is frequently assumed to be impossible because of the sensory loss.

Add to those the autonomic consequences that do not appear in cost reports: blood pressure instability, impaired temperature regulation, and autonomic dysreflexia in injuries at T6 and above — which is a medical emergency and which has its own guide here because everybody around the person needs to recognise it.

The terminology you will see on paper

A short decoder, because people are handed documents full of this.

• C6 AIS B — cervical injury at C6, sensory incomplete.
• T4 complete — thoracic injury at T4, no sacral sparing.
• Sacral sparing — some sensation or motor function in the lowest sacral segments. Determines incompleteness.
• Zone of partial preservation — segments below the level with some remaining function, in a complete injury.
• Spinal shock — the temporary loss of reflexes after acute injury, which resolves and makes early classification unreliable.
• Neurogenic bladder / neurogenic bowel — bladder or bowel dysfunction caused by nerve damage rather than by the organ itself.
• Reflexic versus areflexic — whether reflexes below the injury are present (typically injuries above the sacral segments) or absent (typically injuries affecting the sacral segments or cauda equina). This determines how bladder and bowel programmes are designed.
• Upper motor neuron / lower motor neuron — broadly the same distinction, and a key one for bowel and bladder management.
• Tetraplegia / quadriplegia — the same thing.

Where the NDIS sits

Briefly, because it has its own guide here.

Spinal cord injury causing paraplegia, quadriplegia or tetraplegia is named on NDIS List A. List A is the set of conditions where permanent impairment with substantially reduced functional capacity is taken as given rather than assessed from scratch.

This makes spinal cord injury almost unique in this library. Most of the conditions we write about — epilepsy, cancer-related impairment, brain tumours, Down syndrome — are not on List A, and access is the fight. Here, access generally is not.

What is the fight is adequacy: whether the plan funds enough hours for a bowel programme that takes an hour every second day, the right wheelchair and cushion rather than the cheapest that meets the brief, home modifications that actually work, and workers who are competent in the specific supports the injury requires.

The AlphaBeta report put average annualised NDIS committed supports for spinal cord injury at $142,600 per person, with lifetime government spending on NDIS supports for people with spinal cord injury under 65 estimated at $17.2 billion.

The hard boundary is age. You cannot join the NDIS after turning 65, and the age test applies at the date of application. Given that age-specific incidence peaks at 55 to 64 and remains high at 65 to 74, and that low falls in older people are a growing mechanism, a substantial number of Australians acquire a spinal cord injury on the wrong side of that line. Their pathway is Support at Home through My Aged Care on 1800 200 422, capped at roughly $108,000 a year at the highest classification and means tested — against a scheme with no such cap built on assessed need.

What actually changes outcomes

Having read a great many clinical summaries and plans, the things that distinguish people doing well from people doing badly are consistent, and almost none of them are about the injury.

Specialist spinal unit follow-up that continues. Not just the initial admission. Annual or regular review at a spinal service catches the bladder, skin, shoulder and metabolic problems before they become emergencies.

Renal surveillance that never stops. This is the one most often dropped and it has the clearest historical evidence behind it, set out in the bladder guide here.

Skin that gets looked at by somebody who knows what they are looking at.

Enough funded hours that the bowel programme is not rushed and the person is not transferred by one worker where two are needed.

Shoulders that are protected from year one, not treated from year fifteen.

Equipment prescribed by somebody who knows spinal cord injury, and reviewed when the person or the equipment changes.

Pain and mood treated as real.

Something to do. The productivity loss figure — $21.7 billion, 29 per cent of total cost — is partly a measure of people not working who could.