It destroyed the neural pathways in the affected area of the target's body on a cellular level, turning the tissue into a jelly-like mass and leaving little to repair with traditional means. Additionally, the weapon often inflicted serious brain damage, or simply crashed the autonomous nervous system entirely.
Alfred Harrington saw the damage neural disruptor could cause on a mission to Clematis, and decided to go to medical school on Beowulf in order to search for ways to repair disruptor-affected tissue. Doctor Penelope Mwo-chi took him in as her personal student so they could work on the project together. (HHA6.3: BATB)