A decrease in clonus amplitude by topical anesthesia.
Skin desensitization by topical anesthetic was studied for its effects on the frequency and amplitude of 3 overt involuntary oscillations of the ankle: pathological clonus, physiological clonus, and physiological action tremor. Pathological clonus was studied in two spinal cord patients, physiological clonus in 3 normal subjects following prolonged exercise, and physiological action tremor in 7 normal subjects performing voluntary movements. Topical anesthetic applied to the skin of the leg, ankle and proximal half of the foot resulted in a significant decrease in the amplitude of all 3 oscillations with no significant change in frequency. The effect of topical anesthetic on pathological clonus amplitude was so profound that neither patient could initiate clonus for approximately 30 min, despite repeated attempts to do so. While the mechanism determining the frequencies of these oscillations is a matter of considerable debate, the consistency in their response to topical anesthetic suggests that a common mechanism may exist. A possible clinical application is suggested. Topical anesthetic may be a non-invasive means of attenuating undesirable large amplitude tremors and clonus.
Mills
W J
WJ
Pozos
R S
RS
D000200:Action Potentials / Q000187:drug effects; D000293:Adolescent; D000328:Adult; D000777:Anesthetics / Q000008:administration & dosage; D000842:Ankle / Q000502:physiology*; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D009068:Movement / Q000187:drug effects; D009207:Myoclonus / Q000503:physiopathology; D013116:Spinal Cord / Q000502:physiology
D000777:Anesthetics