Clearly, it is important to make sure that the patient and the physician have come to some agreement on their treatment goals and that technically this is something that is achievable. For example, if you have a patient who has generalized spastic quadraparesis and the patient hopes to walk again, that treatment objective may not be possible simply with the phenol block. On the other hand, if you have a patient with a focal area of profound spasticity such as elbow flexion or thigh adduction, then a phenol block may be very successful in achieving that treatment goal. Wallerian degeneration of neurons occurs in the weeks following injection. The microcirculation around the nerve may also be affected, possibly accounting for longer-term effects.
Most axons eventually regrow, over a variable period of time.
These are very different procedures with different outcomes and different technical requirements. Both techniques require that the injector understand the functional anatomy of the limb that they are treating, understand how to do electrical stimulation to isolate the nerve, and be skilled in using the needle to put the phenol where it is desired. The motor point block is an intramuscular injection done generally in the belly of the muscle, utilizing electrical stimulation techniques to isolate the small motor branches of the nerve innervating muscle fascicles. This requires multiple small dose injections using a very careful technique. This gives you a graded response, that is you can get partial or more complete reduction in muscle contraction using this technically very difficult form of injection.