Which statement correctly describes complete versus incomplete spinal injuries?

• A. Complete injuries have total loss below the injury level; incomplete injuries show variable deficits depending on tract involvement.
• B. Incomplete injuries show the same deficits as complete injuries.
• C. Complete injuries have only sensory loss.
• D. There is no difference between complete and incomplete injuries.

Answer: (A)

The key idea is distinguishing how function below the injury differs when all pathways are disrupted versus when some are spared. A complete spinal injury means a total loss of motor and sensory function below the level of injury—no function preserved in the affected segments. An incomplete injury means some neural pathways remain intact below the injury, so there are partial or variable deficits that depend on which tracts are damaged or spared. Different tracts carry different modalities: motor signals travel in the corticospinal tract, fine touch and proprioception in the dorsal columns, and pain and temperature in the spinothalamic tract. If only certain tracts are affected, you’ll see a mix of preserved and lost functions below the injury, rather than a uniform loss.

That’s why this statement is the best: complete injuries produce a total loss below the lesion, while incomplete injuries show variable deficits based on tract involvement. The other ideas don’t fit because incomplete injuries do not produce the same deficits as complete injuries, complete injuries do not involve only sensory loss, and there is a meaningful difference between complete and incomplete injuries.