Objective: To investigate the effect of peripheral sustained cooling on intent ion tremor in patients with multiple sclerosis(MS). MS induced upper limb intent ion tremor affects many functional activities and is extremely difficult to trea t. Materials/Methods: Deep (18°C) and moderate (25°C) cooling interventions we re applied for 15 minutes to 23 and 11 tremor arms of patients with MS, respecti vely. Deep and moderate cooling reduced skin temperature at the elbow by 13.5°C and 7°C, respectively. Evaluations of physiological variables, the finger tapp ing test, and a wrist step tracking task were performed before and up to 30 minu tes after cooling. Results:The heart rate and the central body temperature remai ned unchanged throughout. Both cooling interventions reduced overall tremor ampl itude and frequency proportional to cooling intensity. Tremor reduction persiste d during the 30 minute post cooling evaluation period. Nerve conduction velocity was decreased after deep cooling, but this does not fully explain the reduction in tremor amplitude or the effects of moderate cooling.Cooling did not substant ially hamper voluntary movement control required for accurate performance of the step tracking task. However, changes in the mechanical properties of musclesmay have contributed to the tremor amplitude reduction.Conclusions: Cooling induced tremor reduction is probably caused by a combination of decreased nerve conduct ion velocity,changed muscle properties, and reduced muscle spindle activity. Tre mor reduction is thought to relate to decreased long loop stretch reflexes, beca use muscle spindle discharge is temperature dependent. These findings are clinic ally important because applying peripheral cooling might enable patients to perf orm functional activities more efficiently.
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