Validation of the optimal site in the neck region for detecting swallowing sounds

Recently, the swallowing sound has been used to detect swallowing events non‐invasively. A previous study, using an accelerometer, showed that the site over the lateral border of the trachea immediately inferior to the cricoid cartilage was the optimal site for detecting swallowing sounds. However, the optimal site for detection of the swallowing sound using a microphone remains undetermined. To validate the optimal site in the neck region for detecting swallowing sounds. Fourteen healthy subjects (mean age, 27·6 ± 2·2 years; seven male and seven female) participated in this study. Twenty condenser microphones were attached to 20 sites on the left neck surface to detect swallowing sounds. Participants were instructed to swallow five different stimuli three times as follows: Resting saliva, 1 and 5 mL of Japanese tea, and 1 and 5 mL of yoghurt. Mean relative peak intensity was used to indicate the magnitude of the swallowing sound. Sound spectrograms were used to illustrate differences in the properties of swallowing sounds. Mean relative peak intensity number was highest in sites at the inferior border of the mandible just above the sternocleidomastoid muscle (site 11) and sites over the lateral border of the trachea immediately inferior to the cricoid cartilage (site 8). Comparison of spectrograms showed a greater density distribution of higher frequency components at site 11 compared with site 8. These results indicate that the inferior border of the mandible just above the sternocleidomastoid muscle is the optimal site for the detection of swallowing sounds.     

Tongue‐mandible coupling movements during saliva swallowing

The purpose of this study was to measure the tongue and mandible positions and displacements in relation to the maxilla in the midsagittal plane to characterize the different saliva swallowing patterns by recording their kinematics. A 2D electromagnetic articulograph using four transducer coils, three attached to the upper surface of the tongue midline plus one attached to the chin anterior part allowed continuous evaluation of tongue and chin movements in twelve young adults in good general health. During 170 s sequences recorded at a frequency of 100 Hz, subjects were at rest, silently reading a text they had chosen. The subjects were free to swallow during the sequence. Deglutition of accumulated saliva was analysed after averaging all values obtained during successive 250 ms periods. We identified three elementary swallowing patterns. Mean duration of tongue‐mandible movements were 1·51 ± 0·17 s, 1·63 ± 0·14 s and 2·00 ± 0·08 s for the first, second and third patterns respectively. In the light of other studies based on intra‐oral pressure recordings, our results help to understand the tongue‐mandible coupling behaviours involved in managing an in‐mouth saliva bolus during the three elementary swallowing patterns identified.     

Incidence of temporomandibular joint clicking in adolescents with and without unilateral posterior cross‐bite: a 10‐year follow‐up study

Among different malocclusions, posterior cross‐bite is thought to have a strong impact on the correct functioning of the masticatory system. The association between unilateral posterior cross‐bite (UPCB) and temporomandibular joint (TMJ) clicking, however, remains still controversial. The aim of this study was to investigate whether the presence of UCPB during early adolescence increases the risk of reporting TMJ clicking after a long‐term follow‐up. A longitudinal survey design was carried out in a group of 12‐year‐old young adolescents, who were examined at baseline for TMJ clicking sounds and unilateral posterior cross‐bite. After 10 years, 519 subjects could be reached by a telephone survey. Standardised questions were used to collect self‐reported TMJ sounds and to determine whether participants had received an orthodontic treatment. Logistic regression analysis revealed a significant association between unilateral posterior cross‐bite and subjectively reported TMJ clicking (odds ratio = 6·0; 95% confidence limits = 3·4–10·8; P < 0·0001). The incidence of TMJ clicking was 12%. At a ten‐year follow‐up, self‐reports of TMJ clicking were significantly associated with the presence of UPCB at baseline, but not with the report of having received an orthodontic treatment. Within the limitation of this study, the presence of unilateral posterior cross‐bite in young adolescents may increase the risk of reporting TMJ sounds at a 10‐year follow‐up. The provision of an orthodontic treatment, however, does not appear to reduce the risk of reporting TMJ sounds.     

Determination of daytime clenching events in subjects with and without self‐reported clenching

To confirm the validity of self‐awareness of daytime clenching, specific electromyogram (EMG) characteristics of clenching behaviour were determined using surface EMG recordings. Temporal muscle EMGs were recorded for 5 h in 13 subjects with self‐reported clenching (clenching group: 27·5 ± 3·8 years old) and 12 subjects without self‐reported clenching (control group: 28·6 ± 7·1 years old). All EMG data were recorded and stored on a portable EMG apparatus. The device was similar in size to a hearing aid, and suitable to record daytime EMG without restriction of daily activities. A clenching event was defined as muscle activity exceeding 10% of the maximum voluntary contraction. Furthermore, simultaneous voice recording was also performed to identify the corresponding EMG event as functional or parafunctional. The mean number of clenching events was 192·8 ± 228·8 and 24·8 ± 26·5 in the clenching and the control groups, respectively (P < 0·05, Mann–Whitney U‐test); the number of functional events was not significantly different between the groups. Because there was a significant difference in the number of clenching events between the groups, self‐reported daytime clenching is considered to be a reliable screening parameter for awake bruxism.     

Evaluation of swallowing ability using swallowing sounds in maxillectomy patients

Maxillectomy for oral tumours often results in debilitating oral hypofunction, which markedly decreases quality of life. Dysphagia, in particular, is one of the most serious problems following maxillectomy. This study used swallowing sounds as a simple evaluation method to evaluate swallowing ability in maxillectomy patients with and without their obturator prosthesis placed. Twenty‐seven maxillectomy patients (15 men, 12 women; mean age 66.0 ± 12.1 years) and 30 healthy controls (14 men, 16 women; mean age 44.9 ± 21.3 years) were recruited for this study. Participants were asked to swallow 4 mL of water, and swallowing sounds were recorded using a throat microphone. Duration of the acoustic signal and duration of peak intensity (DPI) were measured. Duration of peak intensity was significantly longer in maxillectomy patients without their obturator than with it (P < .05) and was significantly longer in maxillectomy patients without their obturator than in healthy controls (P < .025 after Bonferroni correction). With the obturator placed, DPI was significantly longer in maxillectomy patients who had undergone soft palate resection than in those who had not (P < .05). These results suggest swallowing ability in maxillectomy patients could be improved by wearing an obturator prosthesis, particularly during the oral stage. However, it is difficult to improve the oral stage of swallowing in patients who have undergone soft palate resection even with obturator placement.     

Long‐term subjective tongue function after partial glossectomy

There have been limited studies of subjective tongue function over long‐term follow‐up in spite of swallowing and articulation disorders are common complications of glossectomy. To assess long‐term subjective swallowing and articulation function after partial glossectomy. A total of 63 patients with the mobile tongue cancer who underwent partial glossectomy without reconstruction were interviewed to score their swallowing and articulation function on a 100‐point scale. The relation of this subjective scoring to the perioperative data was subjected to multivariate analysis. The mean patient age was 53·4 (19–81) years, and the mean follow‐up duration was 78·9 (14–277) months. Mean swallowing and articulation function score was 87·7 ± 6·1 and 88·6 ± 5·4. Age, follow‐up duration, T stage and resection volume were significantly correlated with swallowing function (P = 0·026, 0·029, 0·016, 0·002, respectively); follow‐up duration was correlated with articulation function (P = 0·039). Patients who undergo partial glossectomy without reconstruction generally demonstrate good function on long‐term follow‐up. Subjective dysfunction was correlated with larger resection volume, older age and shorter follow‐up duration.     

Swallowing frequency in elderly people during daily life

Disuse atrophy of swallowing‐related organs due to an excessive decrease in swallowing frequency is suspected to occur in patients with poor oral intake, especially elderly people. However, swallowing frequency in daily life has not previously been examined in the elderly. This study examined swallowing frequency in elderly people and compared these findings to those in a younger population and differences in the degree of activity in daily life. (i) We compared swallowing frequency in 20 elderly people (82·0 ± 8·3 year) and 15 healthy young people (26·5 ± 3·5 year). (ii) 20 elderly people were divided into two groups according to the degree of activity in daily life: a semi‐bedridden group and bedridden group; the swallowing frequency was compared between these groups. (i) The swallowing frequency in the elderly people was 2–19 times per hour and the mean was 9·4 ± 4·9, and that in the healthy young people was 16–76 times per hour and the mean was 40·7 ± 19·5. Swallowing frequency in elderly people was significantly lower than that in young healthy people (P < 0·0001). (ii) The swallowing frequency in bedridden group was 2–11 times per hour and the mean was 6·8 ± 3·3, and that in semi‐bedridden group was 3–19 times per hour and the mean was 11·9 ± 5·1. Swallowing frequency in bedridden group was significantly lower than that in semi‐bedridden group (P < 0·05). These results indicate that in daily life, elderly people tend to swallow less frequently than young people. In addition, swallowing frequency was lower in elderly subjects with a low degree of activity in daily life.     

Effect of an impaired oral stage on swallowing in patients with Parkinson's disease

We investigated the swallowing function in patients with Parkinson's disease (PD) using deteriorated tongue control because patients with PD frequently exhibit an impaired oral stage of swallowing and the tongue movement affects oral and pharyngeal stage. In total, 201 patients with PD (106 men, 95 women; mean age 70·6 ± 8·0 years; median Hoehn‐Yahr Stage III) were studied. The patients swallowed 10 mL of liquid barium under videofluorography, and their oral transit time (OTT) was measured. Based on 20 healthy controls (mean age 70·3 ± 7·8 years) with an OTT + 2 standard deviation (0·89 + 2 × 0·46) of 1·81 s, the patients with PD were divided into 167 patients with an OTT < 1·81 s and 34 patients with an OTT ≥ 1·81 s. Swallowing function was compared between the groups and assessed using logistic regression analysis. The following factors were significantly associated with oral stage impairment in both groups: tongue‐to‐palate contact, tongue root‐to‐posterior pharyngeal wall contact, premature spillage into the pharynx, aspiration and onset of swallowing reflex. Logistic regression analysis showed that tongue root‐to‐posterior pharyngeal wall contact, onset of swallowing reflex and aspiration were independent factors. PD patients with prolonged OTT displayed poor lingual control and decreased range of motion of the tongue due to bradykinesia and rigidity. Such problems in the oral stage affected the subsequent pharyngeal stage of swallowing with aspiration. Lingual movement in the oral stage thus appears to play an important role in the sequential movement of swallowing in PD.     

Effects of the Paced Auditory Serial Addition Task (PASAT) with different rates on autonomic nervous system responses and self‐reported levels of stress

To characterise self‐reported levels of stress and autonomic responses in healthy humans evoked by different rates of the Paced Auditory Serial Addition Task (PASAT). Fifteen participants performed PASATs with different rates (3·6‐, 2·4‐, 1·6‐ or 1·2‐s intervals) and a control task, in random order. Correct responses, self‐reported levels of stress and autonomic responses to the PASATs were estimated. Increased PASAT rates were associated with decreases in correct responses (P < 0·001) and increases in self‐reported levels of stress (P < 0·001). For autonomic responses, significant changes were seen in 10 variables during 2·4‐s PASAT compared with the respective baseline; however, significant differences in relative changes from baseline were found between the 2·4‐s PASAT and control task only for mean RR‐intervals (P < 0·001), systolic and diastolic blood pressure (P = 0·002 and P = 0·006) and cardiac output (P < 0·001). Regarding comparison between the four PASATs, significant differences in the relative changes from baseline were seen between the 3·6‐s PASAT and faster PASATs, for example mean RR‐intervals, high‐frequency power and respiration rate; however, there were no differences between the faster PASATs. The autonomic responses during the PASATs with different rates were quite similar for the faster PASATs (intervals < 2·4 s); however, the slowest 3·6‐s PASAT evoked significantly less self‐reported stress and autonomic arousal compared with the faster PASATs. Standardization of the PASAT rate may be important for studies on autonomic nervous system function and self‐reported measures of stress. Future studies may test more complex interactions between stress, autonomic responses and pain responses.     

Self‐report of temporomandibular joint clicking and psychological factors: is there an association?

The objectives of this study were to test the hypothesis that self‐reported TMJ clicking sounds in adolescents are positively associated with non‐specific somatic symptoms, self‐perception of body image and care‐seeking behaviour. A cross‐sectional study was carried out in 353 young adolescents (48·4% females) recruited from community (N = 272) and orthodontic clinic (N = 81) settings. Assessments included self‐reported TMJ clicking, non‐specific physical symptoms, body image concerns and for the clinic sample only, the source of motivation for treatment. TMJ sounds were self‐reported by 19% of the sample and were associated with higher scores for non‐specific physical symptoms and body image concerns (P < 0·001). Adolescents who were self‐motivated to seek orthodontic treatment had greater scores for non‐specific physical symptoms, more body image concerns and tended to report TMJ sounds more often (26·3% and 7·7% respectively; P = 0·41) than those who were solely parent/family‐motivated to seek treatment. Self‐reported TMJ sounds in adolescents were associated with a propensity to somatisation and concerns with body image. Care‐seeking adolescents have greater non‐specific physical symptoms and body image concerns and tend to report more frequent TMJ sounds.     

Validity of functional diagnostic examination for temporomandibular joint disc displacement with reduction

The choice of approach for diagnosing temporomandibular joint (TMJ) anterior disc displacement with reduction (ADDR), viz. functional examination or TMJ imaging, is debatable and complicated by findings of low agreement between these approaches. Our aim was to investigate the validity of functional ADDR diagnostics using clinical examination and opto‐electronic mandibular movement recordings versus magnetic resonance imaging (MRI). 53 participants (32 women and 21 men, mean age ± s.d. of 28·7 ± 10·1 years) underwent a clinical examination, mandibular movement recording and MRI of their TMJs within 1 month. All were performed and analysed in a single‐blind design by different experienced examiners for each technique. The sensitivity and specificity of each functional diagnostic method was calculated, with MRI as the gold standard. Anterior disc displacement with reduction was diagnosed in 27·6% of the TMJs clinically, in 15·2% using the movement recordings and in 44·8% on MRI. The specificity of the clinical examination for diagnosing ADDR was 81·0%, and of the movement recordings, 96·6%. The sensitivity was 38·3% and 29·8%, respectively. The chance of having a false‐positive functional diagnosis of ADDR compared with MRI is low, and disagreement between the functional methods and MRI is mainly due to the high number of MRI diagnoses in asymptomatic subjects. In view of the fact that ADDR becomes clinically relevant only when it interferes with TMJ function, the functional diagnostic approach can be considered benchmark in ADDR recognition.     

A pilot study of nocturnal temporalis muscle activity in TMD diagnostic groups of women

Temporomandibular disorder (TMD) incidences are believed to be related to parafunctional behaviours like teeth clenching. This pilot study aimed to (i) develop an automated clench‐detection algorithm, and (ii) apply the algorithm to test for differences in nocturnal clenching in women with and without TMD. Subjects gave informed consent to participate. Adult women were categorised using Diagnostic Criteria for TMD according to presence/absence (+/?) of both TM joint disc placement (DD) and chronic pain (P) into two groups (+DD+P, ?DD?P) with 12 subjects each. Surface temporalis electromyography was recorded during oral tasks performed by subjects at two laboratory sessions. The data were used to characterise muscle activity per N of bite force (μV/N) for each subject, develop the clench‐detection algorithm and test its accuracy. Ambulatory surface temporalis electromyography was self‐recorded by each subject over three nights and analysed using the algorithm and bite force (N) versus muscle activity μV/N calibrations. Bonferroni‐adjusted homoscedastic t‐tests assessed for significant between‐group differences in clenching (P < 0·05). Sensitivity, specificity and accuracy of algorithm‐detected laboratory clenches were all ≥96%. During self‐recordings 95% of clenches had durations of <4 s and peak forces of <10 N in both groups. Mean clench durations were significantly longer (P = 0·042) in +DD+P (1·9 ± 0·8 s) than ?DD?P subjects (1·4 ± 0·4 s). Mean temporalis duty factors (%clench time/total recording time) were significantly larger (P = 0·041) in +DD+P (0·47 ± 0·34%) than ?DD?P (0·26 ±0·22%) subjects. Nocturnal temporalis muscle activities detected by a validated algorithm were longer per clench and recording time in +DD+P compared to ?DD?P women.     

Tongue‐to‐palate resistance training improves tongue strength and oropharyngeal swallowing function in subacute stroke survivors with dysphagia

Tongue function can affect both the oral and pharyngeal stages of the swallowing process, and proper tongue strength is vital for safe oropharyngeal swallowing. This trial investigated the effect of tongue‐to‐palate resistance training (TPRT) on tongue strength and oropharyngeal swallowing function in stroke with dysphagia patients. This trial was performed using a 4‐week, two‐group, pre–post‐design. Participants were allocated to the experimental group (n = 18) or the control group (n = 17). The experimental group performed TPRT for 4 weeks (5 days per week) and traditional dysphagia therapy, whereas the control group performed traditional dysphagia therapy on the same schedule. Tongue strength was measured using the Iowa Oral Performance Instrument. Swallowing function was measured using the videofluoroscopic dysphagia scale (VDS) and penetration–aspiration scale (PAS) based on a videofluoroscopic swallowing study. Experimental group showed more improved in the tongue strength (both anterior and posterior regions, P = 0·009, 0·015). In addition, the experimental group showed more improved scores on the oral and pharyngeal phase of VDS (P = 0·029, 0·007), but not on the PAS (P = 0·471), compared with the control group. This study demonstrated the effectiveness of TPRT in increasing tongue muscle strength and improving swallowing function in patients with post‐stroke dysphagia. Therefore, we recommend TPRT as an easy and simple rehabilitation strategy for improving swallowing in patients with dysphagia.     

Long‐term use of occlusal appliance has impact on sleep structure

Acrylic occlusal appliances (OAs) have been used for temporomandibular disorders and sleep bruxism, but the effects of the treatment are still insufficiently evaluated. Two all‐night polysomnographic recordings were made in a sleep laboratory on 14 bruxists (9 females and 5 males with mean age of 27·5 years). The measurement included basic polysomnography with additional masseter muscle electromyogram and movement recording (static charge‐sensitive bed method) using randomisation. The base night recording was followed by the second study night after 8 weeks regular use of OA. The OA was made on the occlusal surface of the teeth of the upper jaw, and it was used at night time during the study period. With the OA, rapid eye movement sleep changed from 23·3% to 19·6% (P = 0·078), and slow wave sleep increased significantly from 10·2% to 14·7% (P = 0·039). Masseter contraction (MC) episodes occurred with similar frequency (9·7 vs. 10·5 episodes per hour, P = 0·272). The intensity of the rhythmic MC bursts within an episode decreased from 5·5 to 4·4 (P = 0·027). The groups were post hoc divided into responders and non‐responders using a 20% change in MC episode per hour as a cut‐off point. The results indicated that 43% of bruxists increased activity (negative responders), while 36% decreased (positive responders), and in 21%, there was no change in the level. It is concluded that OA does not have significant feedback inhibition on masseter muscle motor activity during sleep. However, OA may increase slow wave sleep.     

Influences of swallowing volume and viscosity on regulation of levator veli palatini muscle activity during swallowing

This study examined the aspect of the regulation of velum movement in the transition from the oral to pharyngeal phases of swallowing in relation to changes in the swallowing volume and viscosity by means of measurment of levator veli palatini muscle activity. The subjects were nine normal adults, ranging in age from 24 to 30 years. The swallowing volume was set at 1/4, 1/2 and 1 volume of the optimum volume of green tea for swallowing determined in each subject, and the viscosity was adjusted to 0, 2·0 and 4·6 Pa·s by mixing with thickener. Nine test foods were prepared in total. The electromyographic activity of the levator veli palatini muscle was monitored using bipolar hooked wire electrodes. The levator veli palatini muscle activity was defined as the integrated electromyographic wave. The mean in swallowing each test food was determined in each subject. The levator veli palatini muscle activity increased with the swallowing volume for all subjects (P < 0·05) and decreased inversely with the viscosity for six subjects (P < 0·05), but no change with the increase in the viscosity was noted for three subjects. This study clarified the aspect of the regulation of velar movement with regard to the involvement of the levator veli palatini muscle in swallowing activity with changes in the swallowing volume and viscosity.     

Effects of the bolus volume on hyoid movements in normal individuals

The hyoid bone moves during swallowing due to contraction of suprahyoid muscles, which are critical components of normal swallowing function. It has been reported that the muscle force and shortening velocity decline gradually with age. Reduced hyoid velocities may delay the sealing of the laryngeal vestibule and opening of the cricopharyngeal muscle. We hypothesised that the hyoid velocity could be a factor influencing aspiration. This study evaluated effects of bolus volume changes on the hyoid distance and velocity in normal swallowing. The subjects were 21 healthy young adults. Lateral projection videofluorography was recorded while each subject swallowed 2·5, 5·0, 10 and 20 mL of liquid barium. We evaluated the maximum hyoid distance (Max d), anterior and superior distance (Max ad, Max sd). And, we evaluated the maximum velocity (Max v), anterior and superior velocity (Max av, Max sv). Two‐way anova test revealed that Max d, Max ad and Max sd for different bolus volumes are not significantly different. But, two‐way anova test showed statistically significant difference in Max v, Max av and Max sv among different bolus volume (P < 0·01). Tukey's test showed that there are significant differences in Max v between 2·5 and 20 mL, 5·0 and 20 mL, 10 and 20 mL, and 2·5 and 10 mL swallowing. And, Tukey's test showed significant differences in Max av and Max sv between 2·5 and 20 mL, 5·0 and 20 mL, and 10 and 20 mL swallowing. It is possible that a larger bolus volume requires greater maximum hyoid velocity. We plan to study hyoid velocity in elderly subjects and in those with dysphagia.     

Continuous measurement of intra‐oral pH and temperature: development,validation of an appliance and a pilot study

To describe a novel approach for continuous measurement of intra‐oral pH and temperature in individuals carrying out normal daily activities over 24 h. We designed, validated and constructed a custom‐made appliance fitted with a pH probe and a thermocouple. Six subjects wore the appliance over a 24‐h period for two non‐consecutive days, while the intra‐oral pH and temperature were measured continuously and recorded. Intra‐oral pH and temperature were very similar across different recording days, the difference being not statistically significant (P ≥ 0·14). There was a noticeable difference in the pattern of variation of pH between day and night. During the day, the mean pH was 7·3 (±0·4) and dropped markedly only after consumption of acidic food and drinks. The intra‐oral pH decreased slowly during sleep with an average pH of 6·6 (±0·4) being recorded. The difference between day and night was statistically significant (P = 0·002). The mean intra‐oral temperature was 33·9 °C (±0·9) during daytime and 35·9 °C (±0·5) during sleep (P = 0·013) with minor fluctuations occurring over 24 h. The continuous and simultaneous intra‐oral pH and temperature measurement system described in this report is reliable, easy to construct, able to measure variables over a sustained period and may serve as a future diagnostic tool in a number of applications.     

Validity of self‐reported sleep bruxism among myofascial temporomandibular disorder patients and controls

Sleep bruxism (SB), primarily involving rhythmic grinding of the teeth during sleep, has been advanced as a causal or maintenance factor for a variety of oro‐facial problems, including temporomandibular disorders (TMD). As laboratory polysomnographic (PSG) assessment is extremely expensive and time‐consuming, most research testing this belief has relied on patient self‐report of SB. The current case–control study examined the accuracy of those self‐reports relative to laboratory‐based PSG assessment of SB in a large sample of women suffering from chronic myofascial TMD (n = 124) and a demographically matched control group without TMD (n = 46). A clinical research coordinator administered a structured questionnaire to assess self‐reported SB. Participants then spent two consecutive nights in a sleep laboratory. Audiovisual and electromyographic data from the second night were scored to assess whether participants met criteria for the presence of 2 or more (2+) rhythmic masticatory muscle activity episodes accompanied by grinding sounds, moderate SB, or severe SB, using previously validated research scoring standards. Contingency tables were constructed to assess positive and negative predictive values, sensitivity and specificity, and 95% confidence intervals surrounding the point estimates. Results showed that self‐report significantly predicted 2+ grinding sounds during sleep for TMD cases. However, self‐reported SB failed to significantly predict the presence or absence of either moderate or severe SB as assessed by PSG, for both cases and controls. These data show that self‐report of tooth grinding awareness is highly unlikely to be a valid indicator of true SB. Studies relying on self‐report to assess SB must be viewed with extreme caution.     

Effect of nasal speaking valve on speech intelligibility under velopharyngeal incompetence: a questionnaire survey

Velopharyngeal incompetence is known as a contributing factor to speech disorders. Suwaki et al. reported that nasal speaking valve (NSV) could improve dysarthria by regulating nasal emission utilising one‐way valve. However, disease or condition which would be susceptible to treatment by NSV has not been clarified yet. This study aimed to evaluate the effect of NSV by questionnaire survey using ready‐made NSV. Subjects were recruited through the internet bulletin, and NSV survey set was sent to the applicant. Sixty‐six participants, who agreed to participate in this study, used NSV and mailed back the questionnaire which included self‐evaluation and third‐party evaluation of speech intelligibility. Statistical analysis revealed that the use of NSV resulted in significant speech intelligibility improvement in both self‐evaluation and third‐party evaluation (P < 0·01). Regarding the type of underlying disease of dysarthria, significant effect of NSV on self‐evaluation of speech intelligibility could be observed in cerebrovascular disease and neurodegenerative disease (P < 0·01) and that on third‐party evaluation in neurodegenerative disease (P < 0·01). Eighty‐six percent of subjects showed improvement of speech intelligibility by shutting up nostrils by fingers, and the significant effect of NSV on both self‐evaluation and third‐party evaluation of speech intelligibility was observed (P < 0·001). From the results of this study, it was suggested that NSV would be effective in cerebrovascular disease and neurodegenerative disease, as well as in subjects whose speech intelligibility was improved by closing nostrils.