Genioglossus Electromyography Research Articles

Association between overnight repetitive respiratory events and the accumulation of genioglossus fatigue in male patients with severe obstructive sleep apnea.

To evaluate the correlation between median frequency (MF) as a measure of genioglossus (GG) fatigue and overnight repetitive respiratory events in male patients with severe obstructive sleep apnea (OSA). GG electromyography (EMG) data were collected synchronously with polysomnography (PSG). Overnight respiratory events were divided based on whether they occurred during the first or second halves of the total number of overnight respiratory events, and differences in MF in the respiratory phase were compared in the same segments. Events were then sampled in pairs to compare MF. The correlation between MF and the order of respiratory events, as well as interindividual differences, were analyzed. Twenty-two male patients were enrolled in this study and 2210 respiratory events were recorded. Before and during respiratory events, MF decreased significantly in the second half, especially during the inspiratory phase (segments 1-4: P = 0.014, P < 0.001, P < 0.001, P < 0.001, respectively). This trend was observed in non-rapid eye movement sleep and lateral position, but not in rapid eye movement sleep or the supine position, and remained after pairing for duration, stage, and position. MF correlated negatively with the order of respiratory events during the inspiratory phase. The trend of decrease in MF only existed in patients with apnea-hypopnea index > 30 events/h. Overnight repetitive respiratory events were associated with increased GG fatigue, influenced by sleep stage and body position in male patients with severe OSA. GG fatigue depends on the order and frequency of respiratory events.

A Novel Method to Classify the Responses of Genioglossus to Negative Pressure in OSA Patients.

This study aims to develop a novel method to classify different genioglossus (GG) responses to upper airway (UA) negative pressure in obstructive sleep apnea (OSA) patients. A single-center, prospective, cohort study. Sleep Medical Center. Patients with OSA underwent drug-induced sleep endoscopy with synchronous genioglossus electromyography (ggEMG) and UA pressure monitoring. In spontaneous obstructive apnea events, the value of epiglottis negative pressure at the end of inspiration (Pepi ) and corresponding peak phasic ggEMG were recorded as pairing data for linear regression analysis to classify GG response modes: peak phasic ggEMG-Pepi linear mode (P < .05) were classified as group 1; others (P ≥ .05) were classified as group 2. Using nasopharyngeal tube (NPT) to reopen the palatopharyngeal cavity for comparing the improvement between the OSA patients with different GG response modes. Sixty subjects were analyzed for GG response modes: 22 patients were in group 1 (r2 = 0.233-0.867), and 38 patients were in group 2. The proportion of partial (63.16% vs 59.09%) or complete (36.84% vs 22.73%) collapse rate of the tongue base in group 2 was significantly higher (χ2 = 7.823, P = .020). The improvement of the apnea-hypopnea index after NPT placement in group 2 was significantly lower than in group 1 (59.09% vs 31.58%, χ2 = 4.339, P = .037). This novel method is advantageous for distinguishing OSA patients with different GG response abilities to UA negative pressure, whose GG responses conforming to peak phasic ggEMG-Pepi linear mode might be more suitable for palatopharyngeal surgery.

O054 Genioglossus neural drive and upper airway dilation in people with obstructive sleep apnoea during wakefulness

Abstract Introduction Genioglossus neural drive and the ensuing tongue dilatory movement may be dissociated in obstructive sleep apnoea (OSA), but this has not been studied. This study aimed to investigate this relationship and its potential role in OSA pathophysiology. Methods During awake nasal breathing in the supine position, inspiratory tongue dilatory movement, quantified with tagged magnetic resonance imaging, and inspiratory peak genioglossus electromyography (EMG) normalised to the maximum voluntary contraction (tongue protrusion), were measured in 4 tongue neuromuscular compartments from 8 controls [apnea-hypopnea index (AHI)&amp;lt;5 events/h] and 34 patients with untreated OSA [AHI&amp;gt;10 events/h]. Results Although larger inspiratory dilatory movement was associated with increased drive to genioglossus (partial Spearman, r=0.23, p=0.016, n=115/68% of compartments), in 14% of the compartments (n=16), there was a large dilatory (&amp;gt;1mm) movement but minimal EMG (&amp;lt;4th percentile). This occurred only in the horizontal compartment. In another group of 18 compartments (16%), there was a large peak EMG (&amp;gt;4th percentile) but minimal dilatory movement (&amp;lt;1mm). This occurred more commonly in the oblique compartments. Dissociation between the amplitude of the peak EMG and inspiratory tongue dilatory movement was most commonly seen in severe OSA patients (AHI&amp;gt;30 events/h, Fisher's exact test, p=0.047). Conclusions Inspiratory tongue dilatory function generally remains closely linked to muscle drive during wakefulness, with larger movement associated with higher peak EMG. However, for approximately one-third of the neuromuscular tongue compartments, neural drive was dissociated from the dilatory motion in severe OSA patients. This may contribute to OSA pathogenesis and have implications for neural stimulation therapy targets.

Electric field aspects in hypoglossal nerve stimulation for obstructive sleep apnea: A bilateral electrophysiological evaluation of unilateral electrode configuration changes.

Hypoglossal nerve stimulation is an established treatment option for obstructive sleep apnea in selected patients. A unilateral hypoglossal nerve stimulation system was approved a decade ago, yet the physiological effect of unilateral hypoglossal stimulation on bilateral tongue motion remains unclear. This study examined how electrode configuration, stimulation cuff position, or body mass index influenced the contralateral genioglossus electromyography (EMG) signal. Twenty-nine patients underwent three EMG recordings in a polysomnographic setting after being implanted with a unilateral hypoglossal nerve stimulator for at least 6 months. The ratio of EMG signals between the ipsi- and contralateral sides was evaluated. No difference in EMG signals was demonstrated based on electrode configurations, stimulation-cuff position, body-mass-index, or sleep apnea severity, even in patients with right tongue protrusion only. Our findings may be explained by a significant level of cross-innervation and by a smaller and less variable circumferential electric field than expected based on prior biophysical models. A patient's individual anatomy needs to be considered during therapy titration in order to achieve an optimal response.

Zolpidem increases sleep efficiency and the respiratory arousal threshold without changing sleep apnoea severity and pharyngeal muscle activity.

A decreased respiratory arousal threshold is one of the main contributors to obstructive sleep apnoea (OSA) pathogenesis. Several recent studies have sought to find a drug capable of increasing the respiratory arousal threshold without impairing pharyngeal muscle activity to reduce OSA severity, with variable success. Here we show that zolpidem increases the respiratory arousal threshold by ∼15%, an effect size which was insufficient to systematically decrease OSA severity as measured by the apnoea-hypopnoea index. Unlike recent physiological findings that showed paradoxical increases in pharyngeal muscle responsiveness during transient manipulations of airway pressure, zolpidem did not alter pharyngeal muscle responsiveness during natural sleep. It did, however, increase sleep efficiency without changing apnoea length, oxygen desaturation, next-day perceived sleepiness and alertness. These novel findings indicate that zolpidem was well tolerated and effective in promoting sleep in people with OSA, which may be therapeutically useful for people with OSA and comorbid insomnia. A recent physiology study performed using continuous positive airway pressure (CPAP) manipulations indicated that the hypnotic zolpidem increases the arousal threshold and genioglossus responsiveness in people with and without obstructive sleep apnoea (OSA). Thus, zolpidem may stabilise breathing and reduce OSA severity without CPAP. Accordingly, we sought to determine the effects of zolpidem on OSA severity, upper airway physiology and next-day sleepiness and alertness. Nineteen people with OSA with low-to-moderate arousal threshold received 10mgzolpidem or placebo according to a double-blind, randomised, cross-over design. Participants completed two overnight in-laboratory polysomnographies (1-week washout), with an epiglottic catheter, intramuscular genioglossus electromyography, nasal mask and pneumotachograph to measure OSA severity, arousal threshold and upper airway muscle responsiveness. Next-morning sleepiness and alertness were also assessed. Zolpidem did not change the apnoea-hypopnoea index versus placebo (40.6±12.3 vs. 40.3±16.4events/h (means±SD), p=0.938) or nadir oxyhaemoglobin saturation (79.6±6.6 vs. 79.7±7.4%,p=0.932), but was well tolerated. Zolpidem increased sleep efficiency by 9±14%(83±11 vs. 73±17%, p=0.010). Arousal threshold increased by 15±5% with zolpidem throughout all sleep stages (p=0.010), whereas genioglossus muscle responsiveness did not change. Next-morning sleepiness and alertness were not different between nights. In summary, a single night of 10mg zolpidem is well tolerated and does not cause next-day impairment in alertness or sleepiness, or overnight hypoxaemia in OSA. However, despite increases in arousal threshold without any change in pharyngeal muscle responsiveness, zolpidem does not alter OSA severity. It does, however, increase sleep efficiency by ∼10%, which may be beneficial in people with OSA and insomnia.

The Role of Genioglossus Activity in Predicting Uvulopalatopharyngoplasty Outcomes.

The aim of this study was to evaluate the association between genioglossus activity during sleep onset and the outcome of uvulopalatopharyngoplasty (UPPP) in patients with obstructive sleep apnea. Case series with planned data collection. Sleep medical center. Forty-four patients with obstructive sleep apnea underwent overnight polysomnography with synchronous genioglossus electromyography (GGEMG) with intraoral electrodes. In addition, all patients underwent revised UPPP with uvula preservation and were followed up with polysomnography at least 3 months after surgery. Twenty-five patients (56.8%) were responders. Multiple regression analysis revealed that increasing tonsil size (odds ratio [OR], 0.086; P = .038) and higher sleep-onset GGEMG (OR, 0.664; P = .04) were significant predictors for surgical success. The area under the receiver operating characteristic curve was 0.942 (OR, 0.040; P < .001) for those predictors, 0.884 for GGEMG, and 0.848 for tonsil size. Moreover, all patients were divided into 4 groups according to tonsil size and sleep-onset GGEMG. The success rate of patients with tonsil size III or IV and sleep-onset GGEMG >11.20% (maximal GGEMG) was optimal (92.9%, 13 of 14), while the success rate of patients with tonsil size I or II and sleep-onset GGEMG ≤11.20% was 0% (0 of 10). Sleep-onset GGEMG and tonsil size are both important in deciding outcomes of UPPP. Patients with tonsil size III or IV and higher sleep onset may be more suitable candidates for UPPP because of the higher probability of surgical success.

Effectiveness of continuous positive airway pressure ventilation in improving genioglossus electromyography in patients with moderate to severe obstructive sleep apnea

Objective: To compare the changes of genioglossus electromyography (GGEMG) with and without continuous positive airway pressure (CPAP) ventilation in moderate to severe obstructive sleep apnea (OSA) patients. Methods: Each of subjects, including male snorers and non-snorers, underwent polysomnography (PSG) with synchronous GGEMG recording with intra-oral bipolar silver ball electrodes at the Sleep Center of Beijing Tsinghua Changgung Hospital from August 2016 to Sepember 2017. Manual CPAP pressure titration and with GGEMG were performed in patients diagnosed moderate to severe OSA. T-test was used to compare the changes of GGEMG in OSA group (n=12, AHI (65.90+23.67) events/h) and control group (n=6, AHI(2.30+1.93) events/h) before and after CPAP treatment. Results: Variables of GGEMG (including tonic, peak and phasic GGEMG) were higher in OSA group than in control group during both wakefulness and non rapid eye movement(NREM) sleep. However, with CPAP treatment, the GGEMG variables were significantly decreased in OSA group during NREM sleep(tonic GGEMG: 1.23%±0.73% vs. 2.54%±1.12%, t=4.024, P=0.002; peak GGEMG: 12.37%±13.19% vs. 26.98%±15.52%, t=2.795, P=0.017; phasic GGEMG: 3.81%±2.47% vs. 8.82%±3.84%, t=5.113, P<0.001). Conclusions: CPAP treatment can eliminate respiratory events and maintain airway patency. It is helpful to normalize the excessive GGEMG response in OSA patients during sleep, which has therapeutic significance to alleviate and prevent genioglossal neuromuscular lesions.

Analysis of the myoelectric characteristics of genioglossus in REM sleep and its improvement by CPAP treatment in OSA patients.

To reveal the characteristics of genioglossus (GG) activation in moderate and severe obstructive sleep apnea (OSA) patients during rapid eye movement (REM) sleep compared with non-rapid eye movement (NREM) sleep and to determine whether continuous positive airway pressure (CPAP) could improve GG activation in OSA patients during sleep. All subjects underwent polysomnography (PSG) with synchronous GG electromyography (GGEMG) recording with intra-oral surface electrodes at baseline on the first night. Only those subjects diagnosed with moderate and severe OSA were included and were manually titrated with CPAP to achieve a therapeutic pressure (Pt) with GGEMG recording on the second night. Nine OSA patients and six normal controls were analyzed in this study. The tonic GGEMG was higher in OSA patients during wakefulness (p = 0.003) and NREM sleep (p = 0.015), but it was not higher in REM sleep (p = 0.862). The average phasic activity of OSA patients was significantly higher in all stages, including wakefulness (p = 0.007), NREM sleep (p = 0.005), and REM sleep (p = 0.021). The peak phasic GGEMG was not different in wakefulness compared with normal controls (p = 0.240), but it was higher in OSA patients in NREM sleep (p = 0.001) and REM sleep (p = 0.021), and it was significantly reduced by using CPAP during sleep (NREM sleep: p = 0.027; REM sleep: p = 0.001). Our results demonstrate that GG activation during NREM and REM sleep is associated with component differences. The tonic component of GGEMG exhibited less of a compensatory increase compared with the phasic component in REM sleep, suggesting that it may be one of the pathological mechanisms of UA collapsibility in REM sleep. In addition, treatment with CPAP can normalize GGEMG activity and mostly reduced the peak phasic GGEMG during sleep.

The effect of genioglossus activity to velopharyngeal surgery in patient with obstructive sleep apnea hypopnea syndrome

Objective: To investigate the effect of genioglossus (GG) activation at sleep onset on the outcome of velopharyngeal surgery in obstructive sleep apnea hypopnea syndrome (OSAHS) patients. Methods: Thirty-five patients between April 2014 and February 2015 in Beijing Tongren Hospital with OSAHS underwent overnight polysomnography with synchronous genioglossus electromyography (GGEMG) using intraoral electrodes. The upper airway (UA) anatomy was evaluated by three-dimensional computer tomography (3D-CT) in OSAHS patients. Then, all of the patients received velopharyngeal surgery, including revised uvulopalatopharyngoplasty (UPPP) with uvula preservation or UPPP combined transpalatal advancement pharyngoplasty. All patients were followed-up using polysomnography 3-6 months after surgery. T-test or Wilcoxon test were used to compare the variables between groups, and Spearman correlation analysis was used to test the correlation between parameters. Results: Thirty-five patients received velopharyngeal surgery. Twenty-two patients (62.86%) were responders, and 13 patients (37.14%) were non-responders. Responders had a higher mean GGEMG during sleep onset (15.31±3.74 vs. 9.92±2.93, t=4.504, P=0.001). The decreased AHI was significantly positively related to the sleep onset mean GGEMG (r=0.541, P=0.004) and the change in GGEMG (r=0.422, P=0.028). The decreased AHI was significantly negatively related to the minimal cross sectional airway area (mCSA,ρ=0.629,P=0.000) and the minimal lateral airway dimension (mLAT, ρ=0.484, P=0.009) at velopharynx. Conclusions: The outcome of velopharyngeal surgery was affected by the mean GGEMG during sleep onset. We speculated that the patient with higher GGEMG at sleep onset and narrower velopharynx were more suitable candidates for velopharyngeal surgery.

Neuromuscular properties of genioglossus activity in healthy adults and obstructive sleep apnea patients

Upper airway patency closely contact with neuromuscular airway regulation during respiratory, especially the activity of the pharyngeal dilators. The genioglossus is the largest pharyngeal dilators with its contraction playing the most important role in keeping the pharyngeal airway open. In healthy individuals, genioglossus activation shows a negative correlation with pharyngeal collapsibility and upper airway resistance. Negative pressure during inspiration can stimulate airway mechanoreceptors to produce a muscle reflex activity. However, in obstructive sleep apnea (OSA) patients, the muscles cannot always compensate for the increased mechanical load, resulting in frequent obstructive breathing events. A number of studies have shown that the collapsibility of upper airway during sleep in OSA patients is closely related to the activity of genioglossus electromyography(GGEMG). The present article describes the current understanding regarding the characters of GGEMG during sleep in healthy adults, as well as the pathophysiology of GGEMG in OSA patients.

Role of medullary astroglial glutamine synthesis in tooth pulp hypersensitivity associated with frequent masseter muscle contraction.

BackgroundThe mechanisms underlying tooth pulp hypersensitivity associated with masseter muscle hyperalgesia remain largely underinvestigated. In the present study, we aimed to determine whether masseter muscle contraction induced by daily electrical stimulation influences the mechanical head-withdrawal threshold and genioglossus electromyography activity caused by the application of capsaicin to the upper first molar tooth pulp. We further investigated whether astroglial glutamine synthesis is involved in first molar tooth pulp hypersensitivity associated with masseter muscle contraction.MethodsThe first molar tooth pulp was treated with capsaicin or vehicle in masseter muscle contraction or sham rats, following which the astroglial glutamine synthetase inhibitor methionine sulfoximine or Phosphate buffered saline (PBS) was applied. Astroglial activation was assessed via immunohistochemistry.ResultsThe mechanical head-withdrawal threshold of the ipsilateral masseter muscle was significantly decreased in masseter muscle contraction rats than in sham rats. Genioglossus electromyography activity was significantly higher in masseter muscle contraction rats than sham rats. Glial fibrillary acidic protein-immunoreactive cell density was significantly higher in masseter muscle contraction rats than in sham rats. Administration of methionine sulfoximine induced no significant changes in the density of glial fibrillary acidic protein-immunoreactive cells relative to PBS treatment. However, mechanical head-withdrawal threshold was significantly higher in masseter muscle contraction rats than PBS-treated rats after methionine sulfoximine administration. Genioglossus electromyography activity following first molar tooth pulp capsaicin treatment was significantly lower in methionine sulfoximine-treated rats than in PBS-treated rats. In the ipsilateral region, the total number of phosphorylated extracellular signal-regulated protein kinase immunoreactive cells in the medullary dorsal horn was significantly smaller upon first molar tooth pulp capsaicin application in methionine sulfoximine-treated rats than in PBS-treated rats.ConclusionsOur results suggest that masseter muscle contraction induces astroglial activation, and that this activation spreads from caudal to the obex in the medullary dorsal horn, resulting in enhanced neuronal excitability associated with astroglial glutamine synthesis in medullary dorsal horn neurons receiving inputs from the tooth pulp. These findings provide significant insight into the mechanisms underlying tooth pulp hypersensitivity associated with masseter muscle contraction.

The Combination of Anatomy and Genioglossus Activity in Predicting the Outcomes of Velopharyngeal Surgery.

Objective This study aims to evaluate the combination of genioglossus (GG) activity and anatomical characteristics in predicting outcomes of velopharyngeal surgery in patients with obstructive sleep apnea (OSA). Study Design Case series with planned data collection. Setting Sleep medical center. Subjects and Methods Forty patients with OSA underwent overnight polysomnography with synchronous genioglossus electromyography (GGEMG) using intraoral electrodes. The upper airway anatomy was evaluated by 3-dimensional computed tomography in patients with OSA. All patients received the same type of velopharyngeal surgery, consisting of revised uvulopalatopharyngoplasty with uvula preservation and concurrent transpalatal advancement pharyngoplasty. We followed up all patients using polysomnography for at least 3 months postoperatively. Results Twenty-five patients (62.50%) were responders, and 15 patients (37.50%) were nonresponders. The decreased apnea-hypopnea index was significantly positively correlated to the sleep onset GGEMG ( P = .006) but was negatively correlated to the change in GGEMG ( P = .013) and tonic GGEMG ( P = .018). Multiple regression analysis revealed that the minimal cross-sectional airway area at the velopharynx (VmCSA) (odds ratio [OR], 1.760; P = .019) and the sleep onset GGEMG (OR, 0.322; P = .043) were significant predictors for surgical outcomes. Combined the two predictors, the area under the ROC curve was 0.901 (OR, 0.789; P = .001) for surgical success, was more valuable than any one predictor. The area under the ROC curve with GGEMG was 0.843, VmCSA was 0.848. Conclusions The combination of sleep onset GGEMG and VmCSA can predict the outcome of velopharyngeal surgery in patients with OSA.

Effects of Depth of Propofol and Sevoflurane Anesthesia on Upper Airway Collapsibility, Respiratory Genioglossus Activation, and Breathing in Healthy Volunteers.

Volatile anesthetics and propofol impair upper airway stability and possibly respiratory upper airway dilator muscle activity. The magnitudes of these effects have not been compared at equivalent anesthetic doses. We hypothesized that upper airway closing pressure is less negative and genioglossus activity is lower during deep compared with shallow anesthesia. In a randomized controlled crossover study of 12 volunteers, anesthesia with propofol or sevoflurane was titrated using a pain stimulus to identify the threshold for suppression of motor response to electrical stimulation. Measurements included bispectral index, genioglossus electromyography, ventilation, hypopharyngeal pressure, upper airway closing pressure, and change in end-expiratory lung volume during mask pressure drops. A total of 393 attempted breaths during occlusion maneuvers were analyzed. Upper airway closing pressure was significantly less negative at deep versus shallow anesthesia (-10.8 ± 4.5 vs. -11.3 ± 4.4 cm H2O, respectively [mean ± SD]) and correlated with the bispectral index (P < 0.001), indicating a more collapsible airway at deep anesthesia. Respiratory genioglossus activity during airway occlusion was significantly lower at deep compared with light anesthesia (26 ± 21 vs. 35 ± 24% of maximal genioglossus activation, respectively; P < 0.001) and correlated with bispectral index (P < 0.001). Upper airway closing pressure and genioglossus activity during airway occlusion did not differ between sevoflurane and propofol anesthesia. Propofol and sevoflurane anesthesia increased upper airway collapsibility in a dose-dependent fashion with no difference at equivalent anesthetic concentrations. These effects can in part be explained by a dose-dependent inhibiting effect of anesthetics on respiratory genioglossus activity.

Relationship of genioglossus muscle activation and severity of obstructive sleep apnea and hypopnea syndrome among Chinese patients

Conclusion: Variability of GGEMG at sleep onset is associated with apnea severity in OSA patients. At sleep onset, a lower decline in GGEMG might suggest a more severe OSA. Objective: The goal of this study was to evaluate genioglossus (GG) activation in the Chinese population at early sleep onset, and clarify the relationship of GG activation and the apnea severity in patients with Obstructive Sleep Apnea (OSA). Methods: Thirty-five OSA patients and 10 normal controls underwent overnight polysomnography with synchronous genioglossus electromyography (GGEMG) using intra-oral electrodes. The upper airway (UA) anatomy was evaluated by three-dimensional computer tomography (3D-CT) in all subjects. Results: The average GGEMG and tonic GGEMG were higher in the apnea patients than in the normal controls during wakefulness and early sleep onset period (three breaths) (p < 0.01). Eight OSA patients had increased GGEMG at sleep onset and 27 patients had decreased GGEMG values. Between the two groups, there were significant differences in the apnea-hypopnea index (AHI), minimal cross-sectional airway area (mCAS) and minimal lateral airway dimension (mLAT) at velopharynx (p < 0.05). The change in GGEMG, phasic GGEMG and tonic GGEMG from awake to sleep showed positive correlations with AHI and negative correlations with velopharynx (mLAT and mCAS) (p < 0.05).

The effects of anesthesia and opioids on the upper airway: A systematic review.

Drug-induced sleep endoscopy (DISE) is used to determine surgical therapy for obstructive sleep apnea (OSA); however, the effects of anesthesia on the upper airway are poorly understood. Our aim was to systematically review existing literature on the effects of anesthetic agents on the upper airway. PubMed, CINAHL, EBM reviews and Scopus (all indexed years). Inclusion criteria included English language articles containing original human data. Two investigators independently reviewed all articles for outcomes related to upper airway morphology, dynamics, neuromuscular response, and respiratory control. The initial search yielded 180 abstracts; 56 articles were ultimately included (total population = 8,540). The anesthetic agents studied were: topical lidocaine, propofol, dexmedetomidine, midazolam, pentobarbital, sevoflurane, desflurane, ketamine, and opioids. Outcome measures were diverse and included imaging studies, genioglossus electromyography, endoscopic airway assessment, polysomnography, upper airway closing pressure, and clinical evidence of obstruction. All agents caused some degrees of airway collapse. Dexmedetomidine did not have dose-dependent effects when evaluated using cine magnetic resonance imaging, unlike sevoflurane, isoflurane, and propofol, and caused less dynamic collapse than propofol. Studies assessing the effect of anesthesia on the upper airway in patients with and without OSA are limited, and few compare effects between agents. Medications with minimal effect on respiratory control (e.g., dexmedetomidine) may work best for DISE.

Temporal characteristics of vowel articulation: Electromyographic investigation of the “articulatory period”

In speech, articulator movement precedes the acoustic signal [e.g., Meyer (1991); Gracco (1988); Lubker and Gay (1982); Bell-Berti and Harris (1981)]. The onset and offset of movement, i.e., the ‘articulatory period' (Bell-Berti and Harris, 1981, p. 13) is said to encompass the acoustic signal however the precise timing and variability of this period are not well understood. Using electromyography (EMG), we examine the onset/offset of the articulatory period as a function of phonetic context. We recorded EMG activity from the posterior and anterior regions of the genioglossus (GG) muscle of the tongue in subjects during the articulation of static vowels, static vowels with initial coronal or palatal fricatives and vowels embedded in the nonce word [∫pVp]. We show front and high vowels entail earlier onset of GG activation and that vowels preceded by coronal fricatives are associated with significantly earlier muscle activation than vowels preceded by palatal fricatives. We also note timing differences between GG regions. Thus, for these stimuli, posterior GG EMG activation encompasses the duration of anterior GG EMG activation. These findings underscore the dynamic nature of lingual movement wherein regional tongue muscle activities exhibit predictable differences determined in large part by phonetic context.

Experience of using electromyography of the genioglossus in the investigation of paediatric dysphagia

The aim of the study was to assess, retrospectively, the utility of genioglossus electromyography (gEMG) in evaluating children with suspected neurogenic feeding and swallowing difficulties. Children who were evaluated using gEMG at a tertiary paediatric neurology dysphagia service were reviewed. Data were analysed by the presence/absence of neurogenic changes on gEMG and the method of feeding at their most recent follow-up. The study group comprised 59 individuals (36 males, 23 females; median age 20 mo; range 1 mo-15 y). The study cohort included individuals with heterogeneous neurological phenotypes (n=40), craniofacial syndrome (n=10), and congenital bulbar palsy (n=9). gEMG identified 35 out of 59 (60%) with neurogenic changes. At follow-up, 24 individuals were on oral feeds and 35 were on alternative methods of feeding (nasogastric /gastrostomy). Eight out of 24 children on oral feeds showed neurogenic changes compared with 27 out of 35 on alternative feeds. χ(2) analysis of feeding method at follow-up and the presence or absence of neurogenic change on EMG was highly significant (p≤0.002). When confounding factors for alternative feeds were accounted for on univariate analysis, the neurogenic changes, severe gastro-oesophageal reflux disease, and respiratory comorbidities were statistically significant in predicting the alternative feeding, whereas growth failure and behavioural difficulties were not significant confounders. Moreover, multiple logistic regression analysis revealed that the neurogenic changes were independently predictive of an alternative method of feeding after adjusting for other confounders with an odds ratio of 29.6 (95% confidence interval 3.97-220; p<0.007). gEMG is a valuable complementary tool in the evaluation of children with neurogenic dysphagia as the degree of severity is independently correlated with long-term feeding outcomes.

Upper Airway Collapsibility

Upper Airway Collapsibility

Pharyngeal pressure and flow effects on genioglossus activation in normal subjects.

Pharyngeal dilator muscles are clearly important in the pathogenesis of obstructive sleep apnea syndrome. Substantial data support the role of local mechanisms in mediating pharyngeal dilator muscle activation in normal humans during wakefulness. Using a recently reported iron lung ventilation model, we sought to determine the stimuli modulating genioglossus activity, dissociating the influences of pharyngeal negative pressure, from inspiratory airflow, resistance, and CO(2). To achieve this aim, we used two gas densities at several levels of end-tidal CO(2) and a number of intrapharyngeal negative pressures. The correlations between genioglossus electromyography (GGEMG) and epiglottic pressure across a breath remained robust under all conditions (R values range from 0.71 +/- 0.07 to 0.83 +/- 0.05). In addition, there was no significant change in the slope of this relationship despite variable gas density or CO(2) levels. Although flow also showed strong correlations with genioglossus activity, there was a significant change in the slope of the GGEMG/flow relationship with altered gas density. For the group averages across conditions (between breath analysis), the correlation with GGEMG was robust for negative pressure (R(2) = 0.98) and less strong for other variables such as flow and resistance. These data suggest that independent of central pattern generator activity, intrapharyngeal negative pressure itself modulates genioglossus activity both within breaths and between breaths.