A spinal cord injury can change life suddenly and profoundly, not only for the person injured but also for their family and those closest to them. Alongside the physical and emotional impact, people often have to understand unfamiliar medical language at a time when they are already dealing with considerable uncertainty.
Terms such as complete injury, incomplete injury, AIS grade, tetraplegia and paraplegia help healthcare professionals describe an injury. However, they do not tell the whole story. Every person’s experience is different, and even people with injuries at a similar level may have different symptoms, abilities, rehabilitation goals and support needs.
Understanding these terms can nevertheless help injured people and families make sense of medical reports and conversations with rehabilitation teams. Accurate classification is also important in a spinal cord injury compensation claim because it helps experts assess the injury’s likely long-term effects and the care, rehabilitation, accommodation, equipment and financial support that may be needed.
This guide explains:
- what the spinal cord does;
- the difference between complete and incomplete spinal cord injury;
- AIS grades from A to E;
- tetraplegia and paraplegia;
- recognised spinal cord injury syndromes; and
- important complications, including autonomic dysreflexia and post-traumatic syringomyelia.
This article provides general information and is not a substitute for individual medical advice or a formal neurological assessment. Anyone concerned about new or changing symptoms should contact their spinal injuries team or another appropriate healthcare professional.
What is the spinal cord?
The spinal cord carries messages between the brain and the rest of the body. These messages include:
- sensory signals, allowing us to feel touch, pressure, pain and temperature;
- motor signals, controlling movement and muscle function; and
- autonomic signals, helping regulate functions that happen without conscious thought, such as blood pressure, sweating, temperature control and bladder and bowel function.
The spinal cord runs from the brainstem through the vertebral canal. It is protected by the vertebral column, surrounding membranes called the meninges, and cerebrospinal fluid.
In adults, the spinal cord usually ends at around the L1–L2 vertebral level. Below this point, the lumbar and sacral nerve roots continue through the spinal canal as a bundle known as the cauda equina.
The vertebral column has five main regions:
- cervical, at the neck;
- thoracic, through the upper and middle back;
- lumbar, in the lower back;
- sacral, at the base of the spine; and
- coccygeal, around the tailbone.
The location of an injury can influence which parts of the body are affected, although its impact will always depend on the individual circumstances.
What is the neurological level of injury?
Healthcare professionals assess spinal cord injuries using the International Standards for Neurological Classification of Spinal Cord Injury, usually shortened to ISNCSCI.
This structured examination assesses sensation and muscle function on both sides of the body. The neurological level of injury is the lowest spinal cord segment where sensory and motor function are found to be normal on both sides.
The neurological level is not necessarily the same as the vertebral level of a fracture, compression or other structural damage shown on an MRI or CT scan. A recorded level such as C4 or T10 will usually describe the findings of the neurological examination unless the clinical record specifically refers to an anatomical vertebral level.
This can be confusing for injured people and families when different levels appear in scan reports, clinical notes and rehabilitation records. The treating spinal injuries team should be able to explain what each recorded level means.
Complete vs incomplete spinal cord injury
Spinal cord injuries are commonly classified as either complete or incomplete. These words have specific medical meanings. They do not simply describe whether the spinal cord looks completely or partially damaged on a scan.
The distinction depends on whether qualifying sensory or motor function remains in the lowest sacral segments, S4–S5. This is known as sacral sparing.
A spinal cord injury is classified as neurologically complete when there is no sensory or motor function in those lowest sacral segments.
An injury is classified as incomplete when qualifying sensory or motor function remains at S4–S5. Clinicians assess this through sacral sensation, deep anal pressure or voluntary anal contraction in accordance with the ISNCSCI criteria.
The word “incomplete” should not be taken to mean that the injury is minor. An incomplete spinal cord injury may still have a profound effect on mobility, independence and day-to-day life. A person may require extensive rehabilitation, personal care, specialist equipment and suitable accommodation.
AIS grades explained
The results of the ISNCSCI examination are recorded using the American Spinal Injury Association Impairment Scale, commonly known as the AIS. Its grades range from AIS A to AIS E.
The AIS developed from the earlier Frankel classification, but the two systems are not interchangeable.
AIS A: complete spinal cord injury
AIS A describes a neurologically complete injury. There is no sensory or motor function preserved in the sacral segments S4–S5.
For example, C4 AIS A describes a complete injury with a neurological level of C4. It does not necessarily mean that structural damage is located at the C4 vertebral level on a scan.
AIS B: sensory-incomplete injury
AIS B describes a sensory-incomplete injury.
Some sensation remains below the neurological level, including qualifying sacral sparing through light-touch or pinprick sensation at S4–S5, or deep anal pressure. However, the criteria for a motor-incomplete injury are not met.
AIS C: motor-incomplete injury
AIS C describes a motor-incomplete injury.
Some muscle function remains below the neurological level, but more than half of the key muscle functions below the single neurological level have a muscle grade below 3. Broadly, this means that most of the key muscles being assessed cannot move through their full range against gravity.
AIS D: motor-incomplete injury
AIS D also describes a motor-incomplete injury.
At least half of the key muscle functions below the single neurological level have a muscle grade of 3 or above. This means that they can move through their full range against gravity.
AIS E: normal function on examination
AIS E indicates that sensory and motor function are normal on the ISNCSCI examination in somebody who previously had deficits arising from a spinal cord injury.
An AIS grade may change following further assessment, treatment or rehabilitation. It is therefore important to consider when an examination took place and whether more recent findings are available.
What is the difference between tetraplegia and paraplegia?
The terms tetraplegia and paraplegia describe the areas of the body affected by the spinal cord injury.
Tetraplegia / Quadriplegia
Tetraplegia, sometimes called quadriplegia, results from an injury to the cervical region of the spinal cord.
It can affect movement or sensation in the arms, trunk, legs and pelvic organs. The extent of those effects varies according to the neurological level and severity of the injury.
Paraplegia
Paraplegia results from an injury to the thoracic, lumbar or sacral regions of the spinal cord.
Arm function is preserved, but the injury may affect the trunk, legs and pelvic organs to varying degrees.
Even people whose injuries have the same recorded level and AIS grade can have very different experiences. Medical classification is important, but it cannot fully describe a person’s independence, challenges, relationships, goals or quality of life.
Hemiplegia, which affects one side of the body, more commonly results from a condition affecting the brain, such as a stroke, rather than from a spinal cord injury. Terms such as triplegia may occasionally be used descriptively but are not formal ISNCSCI classifications.
Recognised incomplete spinal cord injury syndromes
Some incomplete injuries produce recognisable patterns of symptoms.
Central cord syndrome
Central cord syndrome commonly affects the arms and hands more significantly than the legs. Its presentation and severity can nevertheless vary from person to person.
Brown-Séquard syndrome
Brown-Séquard syndrome results from damage mainly affecting one side of the spinal cord. It can cause different patterns of weakness and sensory loss on opposite sides of the body.
Anterior cord syndrome
Anterior cord syndrome affects the front part of the spinal cord. It may cause significant loss of movement and some forms of sensation below the injury.
Conus medullaris syndrome
Conus medullaris syndrome results from damage around the lower end of the spinal cord. It may affect movement and sensation as well as bladder, bowel and sexual function.
Cauda equina syndrome
Cauda equina syndrome affects the lumbosacral nerve roots below the end of the spinal cord. It is anatomically different from a spinal cord syndrome, although it can still cause serious weakness, sensory changes and disturbance of bladder, bowel and sexual function.
What causes a spinal cord injury?
The damaged area of the spinal cord may be described as a lesion.
A traumatic spinal cord injury may result from damage to the vertebrae, discs or ligaments. The spinal cord can be compressed, bruised or stretched and, in some cases, partly or completely severed.
Spinal cord injury can also have non-traumatic causes, including:
- a tumour;
- infection;
- inflammation; or
- interruption of the spinal cord’s blood supply.
Swelling, bleeding and reduced blood flow may contribute to secondary damage after the original event. The full effects of the injury may not therefore be clear immediately, making continued specialist assessment important.
Autonomic dysreflexia: recognising an emergency
Autonomic dysreflexia is a potentially life-threatening complication. It most commonly affects people with spinal cord injuries at or above T6, although it can occasionally occur following a lower injury.
It causes a sudden rise in blood pressure in response to a stimulus below the neurological level of injury. Bladder or bowel distension are common triggers, although there can be others.
Possible warning signs include:
- a sudden or pounding headache;
- sweating or flushing above the injury;
- pale skin or goosebumps below the injury;
- nasal congestion; and
- a slower or, less commonly, faster heart rate.
An increase in systolic blood pressure of around 20 mmHg or more above the person’s usual baseline may be significant.
Suspected autonomic dysreflexia requires immediate action in accordance with the person’s emergency plan and urgent medical assessment. People at risk, and their families or carers, should receive clear clinical advice about how to recognise and respond to an episode.
Post-traumatic syringomyelia
Post-traumatic syringomyelia is another possible complication of spinal cord injury. It occurs when a fluid-filled cavity, called a syrinx, develops within the spinal cord and may enlarge over time.
Symptoms depend on its location and extent. They can include:
- new or increasing pain;
- weakness;
- numbness or other sensory changes;
- loss of reflexes;
- worsening spasticity; or
- changes in bladder or bowel function.
Anyone experiencing new or worsening neurological symptoms after a spinal cord injury should seek prompt medical assessment, even if the original injury happened many years earlier.
Why classification matters in a compensation claim
A spinal cord injury claim is not simply about attaching a label or AIS grade to an injury. It is about understanding how that injury has changed the person’s life and what they may need to live as independently and fully as possible.
The neurological level, AIS grade and medical prognosis can help experts assess future requirements for:
- treatment and specialist rehabilitation;
- personal care and support;
- adapted or more suitable accommodation;
- wheelchairs, equipment and assistive technology;
- mobility and transport;
- education, employment support and loss of earnings; and
- long-term financial security.
The claim should always consider the person behind the medical classification. Two people with apparently similar injuries may have very different family circumstances, occupations, homes, priorities and rehabilitation goals.
Medical evidence may also identify a measurable risk of serious future deterioration, including post-traumatic syringomyelia. In some cases, the legal team may need to consider whether provisional damages are appropriate. This is not automatic and will depend on the individual medical evidence and the applicable legal test.
Spinal cord injury classifications can change
A rehabilitation discharge summary or clinical letter may record a person’s neurological level and AIS grade. Those findings can change as the person is reassessed during treatment and rehabilitation.
A classification recorded in the early stages should not automatically be treated as a complete or permanent account of the person’s condition. The timing of each assessment and the availability of more recent findings are important.
Anyone uncertain about their diagnosis or classification should ask their treating spinal injuries team or rehabilitation clinician for an explanation. In a compensation claim, the solicitor will usually review the relevant medical records and obtain appropriate expert evidence before relying on a particular classification.
How Brethertons can help
Living with a spinal cord injury often means learning unfamiliar medical and rehabilitation terminology at an exceptionally difficult time. Understanding that language may help, but the most important question is what the injury means for the individual and their family.
A spinal cord injury can affect independence, relationships, housing, employment and future plans. Access to suitable rehabilitation, care, equipment and accommodation can make a meaningful difference.
Brethertons’ specialist spinal cord injury solicitors work closely with injured people, their families, rehabilitation professionals and medical experts. We take time to understand the person’s life before the injury, the challenges they now face and what they hope to achieve in the future.
You can find further information on our specialist spinal cord injury solicitors page.
To speak with Jon Rees, Head of Practice Area at Brethertons, call 01788 557671 or email jonrees@brethertons.co.uk.