Effects of repetitive peripheral magnetic stimulation on a patient with severe lower limb muscle weakness due to coronavirus disease-2019.

Kamiue M, Tsubahara A, Ito T. Effects of repetitive peripheral magnetic stimulation on a patient with severe lower limb muscle weakness due to coronavirus disease-2019. Jpn J Compr Rehabil Sci 2024; 15: 27-33. Introduction: A patient developed severe lower limb muscle weakness and gait disturbance after receiving mechanical ventilation in the intensive care unit (ICU) due to coronavirus disease 2019 (COVID-19). We describe the effect of repetitive peripheral magnetic stimulation (rPMS) to strengthen his lower limb muscles. Case: A 70-year-old man was mechanically ventilated due to COVID-19-related breathing difficulties. He was weaned off mechanical ventilation after 54 days, and the tracheostomy was closed after 225 days. However, his lower limbs remained significantly weak, and he was wheelchair-bound for daily activities. Despite approximately 6 months of functional training at a day-service center, his physical function and movement abilities did not improve. Therefore, 30-Hz rPMS was applied to both quadriceps for 20 minutes/day, three times a week, for 4 weeks (12 times). Knee extensor torque (KET) during maximum voluntary contraction (MVC) was greater after (right: 42.1 Nm, left: 40.7 Nm) than before the intervention (right: 33.7 Nm, left: 36.2 Nm). Before the intervention, KET induced by rPMS (rPMS-induced torque) was 0 Nm on both sides, the 30-second chair stand test (CS-30) was challenging to perform, and the walking item score of the Functional Independence Measure (FIM) was 2 points (endurance 30 m). Post-intervention, rPMS-induced torque was 6.5 Nm on the right and 4.7 Nm on the left side, CS-30 could be performed once, and the FIM walking score was improved to 6 points (endurance 60 m). Discussion: The use of rPMS improved lower limb muscle strength in a patient who developed ICU-acquired muscle weakness after COVID-19.

Measurement of Knee Extensor Torque During Repetitive Peripheral Magnetic Stimulation: Comparison of the Forces Induced by Different Stimulators.

OBJECTIVE: To investigate the factors that induce strong contractions during repetitive peripheral magnetic stimulation (rPMS) and compare the muscle torque induced by two stimulators (Stim A and Stim B) with different coil properties. METHODS: rPMS was applied to the right vastus lateralis of 30 healthy young adults. Stim A contained a 10.1 cm2 rectangular iron core coil, while Stim B contained a 191 cm2 round coil. The knee extensor torque (KET) induced by rPMS at 30 Hz was measured isometrically and divided by the maximum voluntary contraction (MVC) to obtain a relative value of MVC (%MVC). KET at 100% intensity of Stim A (A100%, 1.08 T) was compared to those at 100% or 70% intensity of Stim B (B100%, 1.47 T vs. B70%, 1.07 T). Additionally, we conducted a comprehensive literature search for studies that measured the KET during rPMS. RESULTS: Both the mean values of %MVC using B100% and B70% were significantly greater than that using A100%. Furthermore, the KET induced by Stim B was found to be larger than that described in previous reports, unless booster units were used to directly stimulate the main trunk of the femoral nerve. CONCLUSION: Stim B induced a stronger muscle contraction force than Stim A did. This may be because the larger the coil area, the wider the area that can be stimulated. Additionally, a circular coil allows for deeper stimulation.

Factors Involved in Higher Knee Extension Torque Induced by Repetitive Peripheral Magnetic Stimulation.

OBJECTIVE: The study aimed to determine the relationship between knee extension torque induced by repetitive peripheral magnetic stimulation and the characteristics of the participants. DESIGN: This was a basic study with noninvasive intervention. Knee extension torque induced by repetitive peripheral magnetic stimulation (repetitive peripheral magnetic stimulation-induced torque) and maximum voluntary contraction were measured. Stepwise method of multiple regression was performed to determine the factors affecting repetitive peripheral magnetic stimulation-induced torque at 100% intensity and repetitive peripheral magnetic stimulation-induced torque divided by maximum voluntary contraction (percent maximum voluntary contraction). Subcutaneous fat thickness, vastus lateralis muscle thickness measured by ultrasound, maximum voluntary contraction, and mean power frequency of electromyography during maximum voluntary contraction were selected as independent variables. RESULTS: Repetitive peripheral magnetic stimulation was applied to the right vastus lateralis of 30 young healthy adults (average age, 21.1 ± 0.3 yrs). In the multiple regression analysis, repetitive peripheral magnetic stimulation-induced torque ( P < 0.001) was shown to be independently and significantly associated with maximum voluntary contraction (ß = 0.510), subcutaneous fat thickness (ß = -0.358), and vastus lateralis muscle thickness (ß = 0.208), while percent maximum voluntary contraction value ( P < 0.05) was independently and significantly associated with vastus lateralis muscle thickness (ß = 1.059). CONCLUSIONS: Repetitive peripheral magnetic stimulation-induced torque decreases with thicker subcutaneous fat and increases with stronger maximum voluntary contraction or with thicker muscle.

Individual differences in processing ability to transform visual stimuli during the mental rotation task are closely related to individual motor adaptation ability.

Mental rotation (MR) is a well-established experimental paradigm for exploring human spatial ability. Although MR tasks are assumed to be involved in several cognitive processes, it remains unclear which cognitive processes are related to the individual ability of motor adaptation. Therefore, we aimed to elucidate the relationship between the response time (RT) of MR using body parts and the adaptive motor learning capability of gait. In the MR task, dorsal hand, palmar plane, dorsal foot, and plantar plane images rotated in 45° increments were utilized to measure the RTs required for judging hand/foot laterality. A split-belt treadmill paradigm was applied, and the number of strides until the value of the asymmetrical ground reaction force reached a steady state was calculated to evaluate the individual motor adaptation ability. No significant relationship was found between the mean RT of the egocentric perspectives (0°, 45°, and 315°) or allocentric perspectives (135°, 180°, and 225°) and adaptive learning ability of gait, irrespective of body parts or image planes. Contrarily, the change rate of RTs obtained by subtracting the RT of the egocentric perspective from that of the allocentric perspective in dorsal hand/foot images that reflect the time to mentally transform a rotated visual stimulus correlated only with adaptive learning ability. Interestingly, the change rate of RTs calculated using the palmar and plantar images, assumed to reflect the three-dimensional transformation process, was not correlated. These findings suggest that individual differences in the processing capability of visual stimuli during the transformation process involved in the pure motor simulation of MR tasks are precisely related to individual motor adaptation ability.

Foundational Study on the Simple Detection of Impairment Resulting in Dangerous Driving in Patients with Higher Brain Dysfunction.

OBJECTIVES: We performed a survey of medical records to reveal the cognitive deficits behind dangerous driving in patients with higher brain dysfunction. METHODS: Thirty-four patients with higher brain dysfunction were included in this study. Patients' basic characteristics, neuropsychological test results, scores on two types of driving aptitude tests, and accident/near miss data from a driving simulator were extracted from medical records. We conducted χ2 tests for independence between comprehensive driving aptitude scores and "traffic accidents" / "being prohibited from driving as defined by the number of traffic accidents and near misses." Backward logistic regression analysis was carried out to assess correlations of "traffic accidents" and "being prohibited from driving as defined by the number of traffic accidents and near misses" with neuropsychological test scores. RESULTS: No significant correlation was observed between the comprehensive driving aptitude score and "traffic accidents" / "being prohibited from driving as defined by the number of traffic accidents and near misses." The score on the Raven's Colored Progressive Matrices test was the only factor identified as a significant predictor of "being prohibited from driving as defined by the number of traffic accidents and near misses." CONCLUSIONS: The results of this study suggest that it is important to focus on the decline in problem-solving ability as a predictor of "being prohibited from driving as defined by the number of traffic accidents and near misses."

Visual Attention and Motion Visibility Modulate Motor Resonance during Observation of Human Walking in Different Manners.

To advance our knowledge on the motor system during cyclic gait observation, we aimed to explore the effects of gaze fixation on corticospinal excitability evaluated by single-pulse transcranial magnetic stimulation (TMS). Fourteen healthy adult volunteers watched a video of a demonstrator walking on a treadmill under three different conditions: (1) observing the right lower limb, (2) observing the right ankle joint, and (3) observing the right lower limb on a video focused on the area below the knee. In each condition, motor-evoked potentials elicited by TMS in the tibialis anterior (TA) muscle were measured synchronously with the demonstrator's initial contact and toe-off points. Directing visual attention to the ankle joint and focusing on its movements caused corticospinal facilitation in the TA muscle compared with watching the video without any visual fixation. In addition, phase-dependent differences in corticospinal excitability between the initial contact and toe-off points were only detected when the visibility range was restricted to below the knee. Our findings indicated that motor resonance during cyclic gait observation is modulated by visual attention and motion visibility in different activation manners.

Measurement of maximal muscle contraction force induced by high-frequency magnetic stimulation: a preliminary study on the identification of the optimal stimulation site.

Tsubahara A, Kamiue M, Ito T, Kishimoto T, Kurozumi C. Measurement of maximal muscle contraction force induced by high-frequency magnetic stimulation: a preliminary study on the identification of the optimal stimulation site. Jpn J Compr Rehabil Sci 2021; 12: 27-31. Purpose: To identify the optimal stimulation site and technique for inducing strong muscle contraction using a high-frequency magnetic stimulator. Methods: High-frequency magnetic stimulation was administered to the right vastus lateralis (VL) of eight healthy adults at maximal intensity within the range of tolerable pain. The stimulation sites were as follows: section A, the area between the lateral edge of the base of the patella (LEBP) and the distal one-third of the thigh (point D); section B, the area between point D and the proximal one-third of the thigh (point P). Isometric maximal muscle contraction forces induced by magnetic stimulation (Stim-MCF) were compared between the two sections. Results: The Stim-MCF was significantly higher in section B than in section A. Additionally, the sites susceptible to stimulation were confined to a narrow area near point D in section A and the central part between points D and P in section B. The degree of pain was very low in both sections. Conclusion: The optimal site for magnetic stimulation of the VL was limited to the central part of the thigh. In addition to the superficial proximal sub-branch, the deep proximal sub-branch and/or deeply clustered motor nerve endings may have been stimulated. Our results suggested that moving the probe was a useful way to identify the site that elicited the strongest muscle contraction force.

Preventive Effects of Repetitive Peripheral Magnetic Stimulation on Muscle Atrophy in the Paretic Lower Limb of Acute Stroke Patients: A Pilot Study.

OBJECTIVE: The aim of this study was to investigate the effect of repetitive peripheral magnetic stimulation (rPMS) on muscle atrophy prevention in the rectus femoris muscle (RF) of the paretic limb in acute stroke patients. METHODS: Twelve acute stroke patients with a National Institute of Health Stroke Scale score >5 and a motor score of the paretic lower limb >2 at admission were divided into an intervention group (rPMS: mean age, 75±6.4 years) and a conventional care group (non-rPMS: mean age, 62±11.8 years). Baseline measurements were performed within 4 days of stroke onset. In the rPMS group, treatment was applied to the paretic thigh only for 2 weeks, 5 days a week, in addition to conventional care. The cross-sectional area (CSA) of the RF was assessed in both limbs using ultrasound at baseline and 2 weeks later. Data on patient characteristics were collected from the clinical records to assess correlations with the CSA rate of change. RESULTS: Patients in the rPMS group were significantly older. Although the CSA of the RF did not change significantly on either side in the rPMS group, there was a significant decrease in the CSA on the paretic side in the non-rPMS group. However, no significant difference was observed in the CSA rate of change in the rPMS and non-rPMS groups. The CSA rate of change on the paretic side correlated negatively with age in the rPMS group. CONCLUSIONS: Our results suggest that rPMS prevents muscle atrophy more effectively in patients in their 60s than in patients more than 70 years old.

Motor activation is modulated by visual experience during cyclic gait observation: A transcranial magnetic stimulation study.

Transcranial magnetic stimulation (TMS) has been widely utilized to noninvasively explore the motor system during the observation of human movement. However, few studies have characterized motor cortex activity during periodic gait observation. Thus, this study examined the effects of an observer's visual experience and/or intention to imitate on corticospinal excitability during the observation of another's gait. Twenty-six healthy volunteers were included in this study and allocated to two different groups. Participants in the visual experience group had formal experience with gait observation (physical therapist training), while those in the control group did not. Motor-evoked potentials induced by TMS in the tibialis anterior and soleus muscles were measured as surrogates of corticospinal excitability. Participants were seated and, while resting, they observed a demonstrator's gait or observed it with the intention to subsequently reproduce it. Compared with the resting state, cyclic gait observation led to significant corticospinal facilitation in the tibialis anterior and soleus muscles. However, this pattern of corticospinal facilitation in the measured muscles was not coupled to the pattern of crural muscle activity during actual gait and was independent of the step cycle. This motor cortex facilitation effect during gait observation was enhanced by the observer's visual experience in a manner that was not step cycle-dependent, while the observer's intent to imitate did not affect corticospinal excitatory input to either muscle. In addition, visual experience did not modulate corticospinal excitability in gait-related crural muscles. Our findings indicate that motor cortex activity during gait observation is not in line with the timing of muscle activity during gait execution and is modulated by an individual's gait observation experience. These results suggest that visual experience acquired from repetitive gait observation may facilitate the motor system's control on bipedal walking, but may not promote the learning of muscle activity patterns.

Effects of Tongue-Strengthening Exercise on the Geniohyoid Muscle in Young Healthy Adults.

The activities of the suprahyoid muscles have been reported to be induced by tongue muscle contraction. The purpose of this research was to investigate whether tongue-strengthening exercises using a device cause hypertrophy of the geniohyoid muscle in healthy adults. Seven healthy young adults (3 men and 4 women, 21.0 ± 1.3 years old) received 8-week tongue muscle training with the JMS Tongue Pressure Measuring Device. The participants were instructed to press the anterior tongue against the hard palate 30 times in each session, three sessions a day, and 3 days a week. The exercise intensity was set to 60% of maximum tongue pressure in the first week, and to 80% of maximum tongue pressure for the remaining period. The training effect was evaluated by measuring (1) maximum tongue pressure value with the JMS Tongue Pressure Measuring Device, and (2) the area at rest, shortening amount, and contraction ratio of the geniohyoid muscle using ultrasonic imaging. After the 8-week training program, the maximum tongue pressure increased significantly from 44.9 to 61.6 kPa. The area of the geniohyoid muscle at rest also increased significantly from 2.3 to 2.6 cm2 after the program. There were no significant differences in the shortening amounts and the contraction ratios of the geniohyoid muscle between the values before and after the program. The tongue-strengthening exercise was useful to increase the muscle power of the geniohyoid, as well as the tongue muscles, in healthy young adults.

A novel fluoroscopic method for multidimensional evaluation of swallowing function.

OBJECTIVE: Dynamic videofluoroscopic swallow study (VFSS) is used to investigate swallowing movements. However, it requires prolonged radiation exposure and mainly provides qualitative information. Herein, we present a multi-dimensional method for analyzing swallowing based on a pulsed, low-dose fluoroscopy technique that uses serial-shot images and evaluates the size, position, and temporal profile of the bolus to obtain a more comprehensive and realistic analysis of swallowing movements. METHODS: Fifteen healthy adults drank two liquids: 20mL of pure water followed by 20mL of contrast medium mixture in a fluoroscopic study. Data were recorded in serial-shot images (7.5 frames/second, 1024×1024-pixel resolution, DICOM format). The images from the water and contrast swallows were inverted, synchronized, and subtracted to visualize the bolus in each frame. The pathway of the bolus was divided into 15 parts traversing the oropharynx, hypopharynx, and upper esophagus, and the total gray value was measured in each section. The results were presented as contour graphs. RESULTS: The contour graphs allowed for information on the size, anatomical location, and temporal location of the bolus during swallowing to be displayed simultaneously. Two distinct swallowing patterns were observed in the subjects. The bolus showed two peaks-one in the hypopharynx and one in the upper esophagus-in all subjects. However, in nine of the 15 subjects, the two peaks were in different frames, whereas in six of the subjects, the two peaks were in the same frame. CONCLUSION: We developed a new method for quantitatively evaluating swallowing. The technique allows for multidimensional assessment of the size, position, and temporal profile of the movement of the bolus across the pharynx. This method evaluates the swallowing movements using sharp, high-resolution images obtained by serial-shot, pulsed fluoroscopy with low radiation exposure. Additional studies are required to further clarify the variability of swallowing patterns and their clinical relevance in the evaluation of swallowing movements in healthy subjects and in patients with swallowing disorders.

Effects of anterior tongue strengthening exercises on posterior tongue strength in healthy young adults.

OBJECTIVE: The aim of the present study was to investigate whether anterior tongue muscle strengthening exercises can affect the strength of posterior tongue muscles. DESIGN: Eleven healthy subjects (20.6 ± 1.2 years) were included. The subjects exercised by pushing the anterior tongue to the palate 30 times, three times a day, 3 days a week for 8 weeks. The exercise intensity was set at 60% of maximum tongue pressure (MTP) in the first week and 80% of MTP for the remainder of training. After the completion of training, MTP measurements were continued every month for another 3 months to evaluate whether training effects were sustained. RESULTS: MTP was significantly increased after 8 weeks of training compared with before training. No significant differences were seen between MTP immediately after completion of training and MTP 1-3 months after completion of training. However, MTP was significantly higher 1-3 months after completion of training than before training. CONCLUSIONS: The present study showed significant increases in both anterior and posterior MTPs by anterior tongue muscle strengthening exercises. In the future, a database on tongue muscle strengthening exercises in elderly persons, patients with dysphagia, etc. will need to be generated, with the aim of preventing frailty.

Food transit duration is associated with the number of stage II transport cycles when eating solid food.

OBJECTIVE: When eating solids, stage II transport (St2Tr) propels triturated food into the pharynx for bolus formation and storage before swallowing. Although the existence of St2Tr is acknowledged, the reason for its existence remains unclear. Understanding it may facilitate development of food appropriate for individuals with dysphagia. The purpose of this study was to explore how measures of duration of eating and swallowing affect the number of St2Tr cycles. DESIGN: Videofluorography was performed on 13 healthy subjects eating 6-g squares of banana, tofu, and cookies. Measurements included the number of St2Tr cycles, duration of processing (from food entering the mouth to onset of swallowing), pre-upper esophageal sphincter (UES) transit duration (from onset of swallowing to onset of UES transit), UES transit duration (leading edge to trailing edge passing the UES), and total sequence duration (from onset of swallowing to terminal swallow). Principal component (PC) analysis was used to identify factors affecting the number of St2Tr cycles. Analysis of covariance was performed using the 1st PC as an independent variable for predicting the number of St2Tr cycles. RESULTS: All four duration measures were significantly positively correlated with the number of St2Tr cycles. Analysis revealed two orthogonal PCs with variable loading. The 1st PC was a function of the timing variables. The 2nd PC was a function of the number of swallows. CONCLUSIONS: The number of St2Tr cycles was associated with measures of food transit duration and was greater with harder foods before processing and more viscous foods just before swallowing.

Excitability changes in intracortical neural circuits induced by differentially controlled walking patterns.

Our previous single-pulse transcranial magnetic stimulation (TMS) study revealed that excitability in the motor cortex can be altered by conscious control of walking relative to less conscious normal walking. However, substantial elements and underlying mechanisms for inducing walking-related cortical plasticity are still unknown. Hence, in this study we aimed to examine the characteristics of electromyographic (EMG) recordings obtained during different walking conditions, namely, symmetrical walking (SW), asymmetrical walking 1 (AW1), and asymmetrical walking 2 (AW2), with left to right stance duration ratios of 1:1, 1:2, and 2:1, respectively. Furthermore, we investigated the influence of three types of walking control on subsequent changes in the intracortical neural circuits. Prior to each type of 7-min walking task, EMG analyses of the left tibialis anterior (TA) and soleus (SOL) muscles during walking were performed following approximately 3 min of preparative walking. Paired-pulse TMS was used to measure short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) in the left TA and SOL at baseline, immediately after the 7-min walking task, and 30 min post-task. EMG activity in the TA was significantly increased during AW1 and AW2 compared to during SW, whereas a significant difference in EMG activity of the SOL was observed only between AW1 and AW2. As for intracortical excitability, there was a significant alteration in SICI in the TA between SW and AW1, but not between SW and AW2. For the same amount of walking exercise, we found that the different methods used to control walking patterns induced different excitability changes in SICI. Our research shows that activation patterns associated with controlled leg muscles can alter post-exercise excitability in intracortical circuits. Therefore, how leg muscles are activated in a clinical setting could influence the outcome of walking in patients with stroke.

Factors related to low back pain in patients with hip osteoarthritis.

BACKGROUND: The incidence of low back pain (LBP) is high in patients with hip osteoarthritis (OA). Evidence from previous studies suggests that lumbar alignments and hip range of motion (ROM) are important etiological factors for LBP. However, no studies have investigated which factors that have the greatest influence on LBP. OBJECTIVE: This investigation aimed to collectively examine factors related to LBP in patients with hip OA, including lumbar lordosis angle (LLA), leg length discrepancy (LLD), and hip ROM. METHODS: Thirty-five patients participated in this study. LBP was treated as a dependent variable, whereas hip ROMs were treated as independent variables. Patients' age and body mass index (BMI) were recorded as confounding factors, as were LLA and LLD. A logistic regression model was performed to determine the most accurate set of variables to predict LBP. RESULTS: BMI and ROM of hip flexion on the affected side were identified as significant variables. CONCLUSIONS: Our results suggest that BMI and ROM of hip flexion on the affected side are related to LBP in patients with hip OA and need to be assessed.

Effects of volitional walking control on postexercise changes in motor cortical excitability.

To explore the effects of qualitative or quantitative changes in walking on motor cortical excitability, a transcranial magnetic stimulation procedure was used to examine the alterations of motor-evoked potential (MEP) amplitude following walking. Eight healthy participants completed a series of two walking tasks on a treadmill at 2 km/h. The ratio of the left stance duration to the right stance duration was 1 : 2 in the asymmetrical walking task and 1 : 1 in the symmetrical walking task. In each task, walking for 10 min followed by MEP measurement for ∼4 min was repeated three times. MEP measurements were also performed before a walking task as a baseline and continued every 10 min for a further 30 min after the completion of the walking task. During slight voluntary contraction of the left tibialis anterior muscle, MEP measurements were conducted four times. Although a significant MEP depression was found after the asymmetrical walking task with increasing amount of walking, no significant decrease in MEP below baseline was observed after the symmetrical walking task throughout all measurement sessions. This MEP depression was the prominent response to the asymmetrical walking task compared with the symmetrical walking task. These findings indicate that the intentional control of walking pattern has both temporal and task-specific influences on excitability changes in the cerebral cortex, and suggest that motor cortical excitability may be altered by controlling the amount of central commands to the legs even during gait exercise.

Sequential coordination between lingual and pharyngeal pressures produced during dry swallowing.

The aim of this study was to investigate oropharyngeal pressure flow dynamics during dry swallowing in ten healthy subjects. Tongue pressure (TP) was measured using a sensor sheet system with five measuring points on the hard palate, and pharyngeal pressure (PP) was measured using a manometric catheter with four measuring points. The order and correlations of sequential events, such as onset, peak, and offset times of pressure production, at each pressure measuring point were analyzed on the synchronized waveforms. Onset of TP was earlier than that of PP. The peak of TP did not show significant differences with the onset of PP, and it was earlier than that of PP. There was no significant difference between the offset of TP and PP. The onset of PP was temporally time-locked to the peak of TP, and there was an especially strong correlation between the onset of PP and TP at the posterior-median part on the hard palate. The offset of PP was temporally time-locked to that of TP. These results could be interpreted as providing an explanation for the generation of oropharyngeal pressure flow to ensure efficient bolus transport and safe swallowing.

Use of electrical or magnetic stimulation for generating hip flexion torque.

OBJECTIVE: The purpose of this study was to investigate the most suitable site and method to effectively generate isometric hip flexion torque (torque value) using transcutaneous electrical or magnetic stimulation. DESIGN: Eleven healthy volunteers underwent torque value and pain degree measurements during magnetic stimulation of the iliopsoas using three coil placements. After that, the peak torque values generated under three conditions of electrical stimulation of the sartorius, the tensor fasciae latae, and the rectus femoris or that generated by magnetic stimulation of the iliopsoas were recorded at maximum tolerance intensity. RESULTS: No significant differences in torque values were observed among the three coil placements. Magnetic stimulation of the point below the inguinal ligament caused significantly more pain than the other points. Magnetic stimulation of the iliopsoas generated significantly higher torque values than did the electrical stimulation of the two hip flexor muscles together. CONCLUSIONS: The hip joint was one of the most suitable regions for application of magnetic stimulation as an alternative method to electrical stimulation.

Observation of arytenoid movement during laryngeal elevation using videoendoscopic evaluation of swallowing.

The purpose of this study was to confirm that the arytenoid regions dynamically adduct and extend upward toward the epiglottis during laryngeal elevation. While 14 healthy volunteers aged 19-32 years old swallowed 5 ml of white soft yogurt in one gulp without chewing, the movement of the arytenoid regions was observed for videoendoscopic evaluation of swallowing (VE). Each moving image was stored simultaneously on videotape. A cross-sectional area surrounded by the epiglottis and the bilateral arytenoid regions (S) and the length of a straight line passing through the anterior borders of the left and right arytenoid regions (L) were measured. The relative area of the entrance in the laryngeal vestibule was calculated as [S/L (2)] before the swallowing reflex (resting condition), just before laryngeal closure, and just after laryngeal closure. [S/L (2)] was smaller just before epiglottal descent than at the resting condition, and became smallest just after the epiglottis started to ascend. The mean area narrowed to 37.9% of the resting area just after laryngeal closure and in the most extreme case to 8.7% of the resting area. It was demonstrated that the arytenoid regions adducted and extended up toward the epiglottis during laryngeal elevation. The technique used to measure the cross-sectional area of the entrance in the laryngeal vestibule employing VE was an effective analytical procedure.