TRADITIONAL PHARMACOLOGICAL TREATMENTS FOR SPASTICITY - PART-1 - LOCAL TREATMENTS

Spasticity is a velocity-dependent increase in stretch reflex activity . It is one of the forms of muscle overactivity that may affect patien ts with damage to the central nervous system. Spasticity monitoring is relevant to function because the degree of spasticity may reflect the intensity of other disabling types of muscle overactivity such as unw anted antagonistic co-contractions, permanent muscle activity in the a bsence of any stretch or volitional command (spastic dystonia), or ina ppropriate responses to cutaneous or vegetative inputs. In addition, s pasticity like other muscle overactivity can cause muscle shortening, which is another significant source of disability. Finally, spasticity is the only form of muscle overactivity easily quantifiable at the be dside. Under the name pharmacological treatments of spasticity, we und erstand the use of agents designed to reduce all types of muscle overa ctivity, by reducing excitability of motor pathways, at the level of t he central nervous system, the neuromuscular junctions, or the muscle. Pharmacologic treatment should be an adjunct to muscle lengthening an d training of antagonists. Localized muscle overactivity of specific m uscle groups is often seen in a number of common pathologies, includin g stroke and traumatic brain injury. In these cases, we favor the use of local treatments in those muscles where overactivity is most disabl ing, by injection into muscle (neuromuscular block) or close to the ne rve supplying the muscle (perineural block). Two types of local agents have been used in addition to the newly emerged botulinum toxin: loca l anesthetics (lidocaine and congeners), with a fully reversible actio n of short duration, and alcohols (ethanol and phenol), with a longer duration of action. Local anesthetics block both afferent and efferent messages. The onset of action is within minutes and duration of actio n varies between one and several hours according to the agent used. Th eir use requires resuscitation equipment available close by. When a lo ng-lasting blocking agent is being considered, we favor the use of tra nsient blocks with local anesthetics for therapeutic tests or diagnost ic procedures to answer the following questions: Can function be impro ved by the block? What are the roles played by overactivity and contra cture in the impairment of function! Which muscle is contributing to p athologic posturing? What is the true level of performance of antagoni stic muscles! A short-acting anesthetic can also serve as preparation to casting or as an analgesic for intramuscular injections of other an tispastic treatment. Alcohol and phenol provide long-term chemical neu rolysis through destruction of peripheral nerve. Experience with ethan ol is more developed in children using intramuscular injection, while experience with phenol is greater in adults with perineural injection. In both cases, there are anecdotal reports of efficacy but studies ha ve rarely been controlled. Side effects are numerous and include pain during injection, chronic dysesthesia and chronic pain, and episodes o f local or regional vascular complications by vessel toxicity. In the absence of controlled studies, a theoretical comparison of neurolytic agents with botulinum toxin is proposed. Neurolytic agents may be pref erred to botulinum toxin on a number of grounds, including earlier ons et, potentially longer duration of effect, lower cost, and easier stor age. Conversely, pain during injection, tissue destruction with chroni c sensory side effects, and lack of selectivity on motor function with neurolytic agents may favor the use of botulinum toxin. Neurolytic ag ents and botulinum toxin may be used in combination, the former for la rger proximal muscles and the latter for selective injection into dist al muscles. In the future, neurolytic agents may prove more appropriat e in very severely affected patients for whom the purposes of the bloc k are comfort and hygiene. Conversely, botulinum toxin may be better i ndicated in patients for whom there is hope for functional improvement in the affected limb, since the integrity of sensory afferents is ind ispensable. Controlled comparative studies between neurolytic agents a nd botulinum toxin are needed in specific patient populations to help determine the most appropriate applications of each. (C) 1997 John Wil ey & Sons, Inc.