What condition is characterized by a persistent erection resulting from spinal nerve injury?

Priapism is the correct answer because it refers to a prolonged and often painful erection that lasts for several hours and is unrelated to sexual desire or stimulation. This condition can arise from a variety of causes, including spinal cord injuries, which can disrupt the normal function of the nerves responsible for regulating blood flow to the penis.

In cases of spinal nerve injury, the disruption can lead to an imbalance in the mechanisms that control penile erection, causing it to remain engorged with blood for an extended period. This prolonged erection can potentially lead to tissue damage and other complications if not treated.

The other options do not pertain to the condition described. Erectile dysfunction involves difficulty achieving or maintaining an erection, hemorrhoids are swollen veins in the rectal area, and testicular torsion is a condition where the spermatic cord becomes twisted, leading to loss of blood supply to the testicle. None of those conditions involve the prolonged and uncontrolled erection characteristic of priapism.