An incomplete spinal cord injury means that some messages can still travel to or from the brain below the injury. A person may retain some sensation, function, or muscle control, but the pattern can be very uneven: a hand may be weaker than a leg, pain sensation may differ from light touch, or movement may return without normal feeling. The defining question is not simply whether a person can move. It is whether sensory or motor function remains in the lowest sacral segments, S4–S5.
What an incomplete spinal cord injury means in a neurological exam
Clinicians call an injury incomplete when there is sacral sparing: sensory or motor function is preserved at S4–S5. With this finding, at least some pathways across the injured area are still functioning. By itself, it does not tell the whole story of strength, independence, pain, bladder function, or walking. Instead, it establishes a starting point for a more detailed neurological classification.
For that classification, clinicians use the International Standards for Neurological Classification of Spinal Cord Injury, or ISNCSCI. During the examination, they test 28 dermatomes for sensation and 10 key muscles on each side of the body. Taken together, those results identify the neurologic level of injury, determine whether the injury is complete or incomplete, and assign an AIS grade.
For example, someone with a thoracic injury may have no useful leg movement yet still report sensation at S4–S5 or show a voluntary anal contraction. The injury is then incomplete by definition. Conversely, a little movement elsewhere below an injury does not, by itself, establish that the injury is incomplete.
A spinal cord injury needs formal medical assessment, not self-testing. Seek medical care promptly for new or changing weakness, sensation, bowel or bladder function, or other symptoms after a spinal injury.
Complete versus incomplete injury: why sacral sparing decides the label
When no sensory or motor function is preserved in S4–S5, a complete injury is classified as AIS A. By contrast, an incomplete injury has preserved sacral sensory or motor function. In clinical classification, the distinction rests on this sacral examination, not on a quick observation of whether a person can move a toe or feel an area of skin below the injury.
What clinicians check at S4–S5
- Light-touch sensation
- Pinprick sensation
- Deep anal pressure
- Voluntary anal contraction
Together, these four findings can clarify a classification that otherwise looks confusing. In studies in which the first examination occurred 72 hours after injury, 84% of people initially classified AIS A remained complete; about 10% changed to AIS B and 5% to AIS C. When the first exam took place at 30 days, 95% remained complete. For prognosis, the neurological exam at 72 hours has more value than an exam during the first 24 hours.
How ASIA Impairment Scale B, C, and D describe remaining function
The ASIA Impairment Scale, usually shortened to AIS, turns the examination into a common language for the rehabilitation team. Rather than promise one person’s recovery, it describes exam findings. In sensory testing, each point is scored from 0 for absent to 1 for impaired and 2 for normal. Together, light touch and pinprick can total 112 points.
| AIS grade | What the grade means |
|---|---|
| AIS B | Sensory incomplete: sensory function is preserved at S4–S5, but not motor function; no motor function is preserved more than three levels below the motor level on either side. |
| AIS C | Motor incomplete: motor function is preserved through voluntary anal contraction or through motor function more than three levels below the motor level with sensory sparing; fewer than half of key muscles below the neurologic level have strength of at least 3/5. |
| AIS D | Motor incomplete: the motor-incomplete criteria are met, and at least half of key muscles below the neurologic level have strength of at least 3/5. |
In six steps, the process determines the neurologic level of injury (NLI), tests sensation, tests motor function, establishes complete or incomplete status, assigns the AIS grade, and documents the zone of partial preservation. By definition, the NLI is the lowest spinal cord segment with normal sensory and motor function on both sides. It is not interchangeable with the bony level seen on imaging or with a person’s day-to-day abilities.
Spinal cord injury levels and syndromes reveal different patterns
On the standardized exam, spinal cord injury levels describe where normal sensory and motor function ends. Alone, they do not explain every symptom. Affected pathways can also produce an incomplete syndrome. In clinical practice, the five incomplete syndromes are central cord syndrome, Brown-Séquard syndrome, anterior cord syndrome, posterior cord syndrome, and cauda equina syndrome.
Central cord syndrome can affect the arms more than the legs
Central cord syndrome accounts for about 44% of traumatic incomplete spinal cord injuries. It is the most common incomplete syndrome and is especially associated with older adults who have cervical stenosis after a low-energy hyperextension fall. Its hallmark is greater motor impairment in the upper limbs than in the lower limbs. Dissociated sensory loss and bladder dysfunction are also common. Spontaneous improvement is typical, and many people regain walking ability, particularly when there is no instability and treatment is conservative.
Three less common pathway patterns
- Brown-Séquard syndrome: injury to one half of the cord. The classic pattern combines same-side spastic paralysis and loss of proprioception with opposite-side loss of pain and temperature. Pure hemisection is rare; most cases are partial.
- Anterior cord syndrome: affects the front two-thirds of the cord, often from ischemia in the anterior spinal artery territory. Motor function and pain and temperature sensation are lost while proprioception and vibration are preserved. Its prognosis is the poorest among incomplete syndromes because motor pathways are directly affected.
- Posterior cord syndrome: the rarest incomplete syndrome, with an incidence below 1%. Loss of proprioception, fine touch, pressure, and vibration below the lesion can lead to ataxia and an unsteady gait.
These labels describe recognizable patterns; they do not replace the full ISNCSCI examination.
Recovery has a fast early phase and a longer course
Motor recovery is generally fastest during the first three months. Most motor recovery occurs within six to nine months, and spontaneous motor recovery commonly reaches a plateau between 12 and 18 months. Still, that timeline is useful for setting expectations, not a deadline or an individual forecast.
During rehabilitation, AIS grade can change. Among people with AIS C injuries, as many as 85% improved to AIS D or E within six to 12 months, while about 10% to 20% remained AIS C. Across all injury types, the amount and pattern of preserved sensation and strength, age, injury level, and the timing of the examination all matter. Through repeated examinations, a rehabilitation team can explain what has changed rather than treating an early grade as a fixed future.
Can you walk with incomplete paraplegia?
With incomplete paraplegia, some people regain walking, sometimes with orthoses or assistive devices. Even so, the term incomplete does not guarantee walking. At the group level, the strongest clues include AIS grade, preserved pinprick sensation, early leg strength, and age.
In one set of findings, all people with AIS D were able to walk at discharge from inpatient rehabilitation. At six months, independent walking with devices was reported in 92% of people with AIS C injuries involving an upper motor neuron pattern, 35% of people with AIS B injuries, and 100% of people with AIS D injuries. For AIS C, reported walking rates were 71% to 91% for people younger than 50 and 25% to 42% for people older than 50.
Within AIS B, the overall walking recovery rate was about 33%, but sensory details made a large difference. When pinprick sensation was preserved, reported rates were 66% to 89%; with light touch alone, they were 0% to 33%. A lower-extremity motor score of at least 10 out of 50 after one month strongly predicted walking at one year in people with incomplete paraplegia. Reaching quadriceps strength of at least 3/5 within two months was also a strong predictor; only 25% of people without that strength achieved walking ability. These are outcomes in groups, not a forecast for any individual.
Locomotor training puts repeated practice to work
After incomplete SCI, locomotor training uses repeated, task-specific sensory input and movement practice to improve walking function. In body-weight-supported treadmill training (BWSTT), body-weight support is adjusted for the individual while stepping practice continues. As another approach, defined overground mobility training builds mobility practice away from the treadmill.
In the multicenter SCILT trial of 146 participants, BWSTT and defined overground mobility training produced no significant difference in outcomes at six months; both improved walking ability. In a chronic incomplete SCI group that averaged 7.4 years after injury, 12 months of BWSTT three times each week, or 144 sessions, reduced the required body-weight support by 54% and increased treadmill speed by 180%. Six of 14 participants improved overground walking, and the gains remained stable eight months after training ended.
Behind this approach is activity-dependent neuroplasticity: repeated, task-specific sensory stimulation can improve motor output. Within the spinal cord, a central pattern generator for locomotion can produce rhythmic movement. Training does not erase an injury, and a method should be chosen with the rehabilitation team around a person’s safety, goals, and changing exam findings.
Four misconceptions can obscure the next useful question
- Incomplete means I will walk. Incomplete means sacral function is preserved. Walking outcomes vary widely, and some people need braces or assistive devices.
- Any movement proves the injury is incomplete. By definition, completeness is decided by S4–S5 sensory or motor function, not movement alone.
- One AIS grade tells me exactly what will happen. AIS grades describe a standardized exam. Added context comes from age, sensory findings, early strength, injury pattern, and repeated assessments.
- If the first weeks pass, recovery is over. Although motor change is fastest early, recovery commonly continues through six to nine months and may plateau at 12 to 18 months.
Frequently Asked Questions
What is an incomplete spinal cord injury?
It is a spinal cord injury with preserved sensory or motor function in S4–S5. A person may have some sensation, function, or muscle control below the injury, but the pattern can differ greatly from one person to another.
What is the difference between complete and incomplete spinal cord injury?
A complete AIS A injury has no sensory or motor function at S4–S5. An incomplete injury has sacral sparing. The distinction is based on the sacral exam, not simply on visible movement below the injury.
Can you recover from an incomplete spinal cord injury?
Incomplete injuries generally show more recovery than complete injuries. Motor recovery is fastest in the first three months, commonly continues through six to nine months, and often reaches a plateau by 12 to 18 months.
Can you walk with incomplete paraplegia?
Some people can walk, often with therapy, orthoses, or other devices. AIS grade, age, preserved pinprick sensation, and early leg strength are among the findings associated with group-level walking outcomes.
What are the types of incomplete spinal cord injury?
The five clinical incomplete syndromes are central cord, Brown-Séquard, anterior cord, posterior cord, and cauda equina syndromes. A formal neurological examination is needed to classify an individual injury.
