森 志乃

OBJECTIVE: Head lift exercise is a widely known form of training in the rehabilitation of patients with dysphagia. This study aimed to compare muscular strength reinforcement training of the suprahyoid muscles using repetitive peripheral magnetic stimulation (rPMS) with head lift exercises in a randomized controlled trial. MATERIALS AND METHODS: Twenty-four healthy adults were randomly assigned to either the magnetic stimulation group (M group) or the head lift exercise group (H group). Both groups underwent training five days a week for two weeks. The primary outcome was the cervical flexor strength, and secondary outcomes were jaw-opening force, tongue pressure, muscle fatigue of the hyoid and laryngeal muscles, displacement of the hyoid bone and opening width of the upper esophageal sphincter (UES) while swallowing 10 mL of liquid, training performance rate, and pain. RESULTS: No dropouts were reported during the two-week intervention period. Cervical flexor strength significantly increased solely in the M group. Tongue pressure significantly improved in both groups. There were no significant differences in the jaw-opening force, median frequency rate of the anterior belly of the digastric muscle, sternohyoid muscle, sternocleidomastoid muscle, anterior and superior hyoid bone displacement, and UES opening width in both groups. CONCLUSIONS: Two-week rPMS of the suprahyoid muscles increased the strength of these muscles compared with the head lift exercise during the same period.

OBJECTIVES: Neuromuscular electrical stimulation has been widely used in patients with dysphagia. However, obtaining sufficient hyoid bone movement through surface electrodes seems difficult. The aim of this study was to evaluate hyoid bone movement at rest through peripheral magnetic stimulation of the suprahyoid muscles in normal individuals. METHODS: Healthy adult men were recruited. A specially designed coil was connected to the peripheral magnetic stimulator. The coil was placed on the submental area of the subjects. Magnetic stimulation was performed at 30 Hz for 2 sec. The intensity level selected induces hyoid bone movement without causing intolerable pain to the subjects. The hyoid bone at rest between on- and off-magnetic stimulations of the suprahyoid muscles were identified using fluoroscopy at 30 frames/sec in lateral projection. Pain during peripheral magnetic stimulation was evaluated using the numerical rating scale (NRS). RESULTS: Eleven subjects aged 32 ± 9 years participated in this study. Magnetic stimulation resulted in 10.9 ± 2.8 mm forward displacement and 8.3 ± 4.1 mm (mean ± SD) upward displacement of the hyoid bone. The median NRS score during magnetic stimulation was 1. CONCLUSIONS: Peripheral magnetic stimulation is noninvasive and easy to perform. It does not require skin preparation, facilitates sufficient hyoid bone movement, and causes minimum level of pain.