A family with paramyotonia congenita (PC) is presented. At least 10 family members were affected in an autosomal dominant inheritance pattern. The proband had cold-sensitive muscle stiffness, paradoxical myotonia, and intermittent muscle weakness since childhood. The serum level of creatine kinase was mildly elevated and short exercise test with cooling revealed a drastic reduction of compound muscle action potentials with repetitive discharges. Muscle biopsy revealed marked variation in the fiber size and increased internal nuclei. The molecular biological study revealed a common missense mutation (Arg1448Cys) at the voltage-gated sodium channel gene (SCN4A). The repetitive CMAP discharges during short exercise test with cooling observed in the proband has not been reported previously. This observation needs to be confirmed among PC patients with different mutations. This is the first report on a PC family confirmed by the molecular biological technique in Korea.

Normal walking on staircases is a very important ordinary activity. It is a complicated motion that requires a big muscular strength and moment, and a big joint exercise scope. Due to such characteristics, staircase walking may be an obstacle to those with weakened lower limb muscle strength, and actually, fall injury accidents occur. Existing studies focus on dynamic changes in staircase walking. However, this study aimed to analyze staircase-walking characteristics evidenced when applying vibratory somatosensory stimulus to the ankle joint in a bid to reduce the risk of fall injuries associated with staircase walking. Five elderly male subjects, who had no disease related to the musculoskeletal system, participated in experiments. Experiments were held in a motion analysis laboratory equipped with 3-D motion analysis systems, force platforms, etc. In order to gather motion data, subjects wore markers and vibratory stimulation devices designed to apply somatosensory stimulus to ankle joints, and climbed down a staircase with the height adjusted appropriately. Using motion data gathered from staircase-walking, the ankle joint, knee joint and hip joint angles were obtained, and thus each joint's contribution to the motion was calculated. In the case of vibratory somatosensory stimuli being applied to the Achilles's tendon, the ankle joint contributed more to the motion of climbing down a staircase than the knee joint and the hip joint did. On the other hand, in the case of vibratory somatosensory stimulus being applied to the anterior tibialis, the ankle joint contribution was lowered, and to make up for it, the knee joint and the hip joint contribution increased. This outcome revealed that the effect of the vibratory somatosensory stimulation applied to the ankle joint can appear in not only the ankle joint, but also in the whole lower limbs due to chain reaction.