The bad news about nerve damage is that the top often has no way to know when it is happening, other than communicating with their bottoms! This means that rope tops have a serious responsibility to educate their bottoms to alert them when they have bad pain/sensations so that they can release/adjust the bondage.
Other than educating and empowering their bottoms, tops can help prevent these injuries by knowing basic nerve anatomy and symptoms of nerve damage. Anecdotally, it seems that most problems with bondage are caused by damage to the radial nerve (aka “honeymoon palsy” or “Saturday night palsy”), in most cases due to tight or load bearing ties across the upper arms. The radial nerve wraps around the upper arm and is close to the surface around the bottom of the deltoid, where people love to put rope (especially in box ties and the like). Other forearm nerves include the medial and ulnar nerves. Note that the exact location of these nerves varies from person to person, and both location and degree of exposure will vary based on position!
Tops should watch for signs of trouble – signs like wiggling fingers and adjusting ropes are good cues that it’s time to check in with the bottom and adjust the bondage.During the scene a bondage top can check CSM (circulation, sensation, and movement) in all sorts of fancy medical ways (capillary refill, point differentiation, etc)- however, it's important to keep in mind that the main predictor of bad outcomes seems to be the bottom’s subjective experience in the bondage. Pay attention to body language and check in frequently.
In addition to testing for sensation, there are several motor "tests" the top can do:
The Kumar Test is designed to check all three of the nerves of the hand (radial, ulnar, and median). This test basically involves making the "OK" sign with the hand/fingers – please follow the link for details. 17
Ask the bottom to touch the tip of each finger to their thumb. Inability to do this can indicate a problem with the radial, ulnar, or median nerve. 16
If the bottom is in a position to do so, have them make their wrist and fingers a straight line with their forearm. Put your hand on the fingernail side of their hand. Have them extend their wrist (bend at the wrist towards your hand, away from the direction of their palm- this is called "wrist extension"). Inability to do this generally indicates a problem with the radial nerve (often from a box/TK tie).
Ask the bottom to spread out ("extend") their fingers, by themselves and against resistance. Inability to do this indicates a problem with the radial nerve, or if they specifically cannot extend the thumb, the median nerve.
Ask the bottom to squeeze your fingers and *maintain* a grip. Inability to do this can indicate damage to the medial nerve or the ulnar nerve.2
If the bottom "fails" any of these tests, that is an indication that they have some nerve impairment and should be untied.
However, “passing” any of these tests is NOT an “all-clear” that would indicate everything is definitely OK.
Making frequent shifts in the rope – just a slight reposition, adjusting the tension, or temporarily releasing the pressure to allow the underlying tissues to readjust- can make all the difference. This may be as simple as running fingers under the rope or as complicated as rearranging a suspension so the bottom is in an entirely different position.