Pharyngeal Stimulation Research Articles

A Comparative Study in Assessing the Improvement of Dysphagia in between Ischemic and Hemorrhagic Stroke of Subacute Stage Using Pharyngeal Neuromuscular Electrical Stimulation and Mendelsohn Manuever

A Comparative Study in Assessing the Improvement of Dysphagia in between Ischemic and Hemorrhagic Stroke of Subacute Stage Using Pharyngeal Neuromuscular Electrical Stimulation and Mendelsohn Manuever

Effects of pharyngeal electrical stimulation on swallowing performance.

Pharyngeal electrical stimulation (PEStim) has been found to facilitate voluntary swallowing. This study investigated how PEStim contributed to modulation of swallowing function in 15 healthy humans. In the involuntary swallowing test, water was injected onto the pharynx at 0.05 ml/s and the onset latency of the first swallow was measured. In the voluntary swallowing test, subjects swallowed their own saliva as quickly as possible for 30 s and the number of swallows was counted. Voluntary and involuntary swallowing was evaluated before (baseline), immediately after, and every 10 min after 10-min PEStim for 60 min. A voluntary swallowing test with simultaneous 30-s PEStim was also conducted before and 60 min after 10-min PEStim. The number of voluntary swallows with simultaneous PEStim significantly increased over 60 min after 10-min PEStim compared with the baseline. The onset latency of the first swallow in the involuntary swallowing test was not affected by 10-min PEStim. The results suggest that PEStim may have a long-term facilitatory effect on the initiation of voluntary swallowing in healthy humans, but not on peripherally-evoked swallowing. The physiological implications of this modulation are discussed.

Pharyngeal electrical stimulation device for the treatment of neurogenic dysphagia: technology update.

Neurogenic dysphagia (ND) can occur in patients with nervous system diseases of varying etiologies. Moreover, recovery from ND is not guaranteed. The therapeutic approaches for oropharyngeal ND have drastically changed over the last decade, mainly due to a better knowledge of the neurophysiology of swallowing along with the progress of neuroimaging and neurophysiological studies. For this reason, it is a priority to develop a treatment that is repeatable, safe, and can be carried out at the bedside as well as for outpatients. Pharyngeal electrical stimulation (PES) is a novel rehabilitation treatment for ND. PES is carried out via location-specific intraluminal catheters that are introduced transnasally and enable clinicians to stimulate the pharynx directly. This technique has demonstrated increasingly promising evidence in improving swallowing performance in patients with ND associated with stroke and multiple sclerosis, probably by increasing the corticobulbar excitability and inducing cortical reorganization of swallowing motor cortex. In this article, we update the reader as to both the physiologic background and past and current studies of PES in an effort to highlight the clinical progress of this important technique.

Early Endoscopic Intervention for an Accidentally Swallowed Toothbrush: A Case Report

INTRODUCTION Esophageal foreign bodies can be diagnosed at any age, especially in childhood. The most efficient treatment method is the endoscopic removal of the object. Early diagnosis and treatment of the esophageal foreign bodies are crucial regarding the possible fatal outcome due to complications. In the literature, there has been a few cases which were presenting ingested huge foreign bodies like swallowing toothbrush. The aim of this case report is to presenting a successful minimally invasive emergency management of this rarely emerging clinical entity. CASE SUMMARY We presented a case of a 23-year-old female patient, who accidentally ingested toothbrush while trying to induce emesis by pharyngeal stimulation using it. After physical, laboratory and radiological examinations were done, obstructed toothbrush was successfully removed endoscopically within two hours, and she was discharged without any complications after 24-h observation. CONCLUSION Emergent endoscopic intervention is a promising minimally invasive approach for retrieving of the ingested esophageal foreign bodies to prevent possible fatal course of the complications.

Introducing a Virtual Lesion Model of Dysphagia Resulting from Pharyngeal Sensory Impairment

Background/Aims: Performing neurophysiological and functional imaging studies in severely affected patients to investigate novel neurostimulation techniques for the treatment of neurogenic dysphagia is difficult. Therefore, basic research needs to be conducted in healthy subjects. Swallowing is a motor function highly dependent on sensory afferent input. Here we propose a virtual peripheral sensory lesion model to mimic pharyngeal sensory impairment, which is known as a major contributor to dysphagia in neurological disease. Methods: In this randomized crossover study on 11 healthy volunteers, cortical activation during pneumatic pharyngeal stimulation was measured applying magnetoencephalography in two separate sessions, with and without pharyngeal surface anesthesia. Results: Stimulation evoked bilateral event-related desynchronization (ERD) mainly in the caudolateral pericentral cortex. In comparison to the no-anesthesia condition, topical anesthesia led to a reduction of ERD in beta (13-30 Hz) and low gamma (30-60 Hz) frequency ranges (p<0.05) in sensory but also motor cortical areas. Conclusions: Withdrawal of sensory afferent information by topical anesthesia leads to reduced response to pneumatic pharyngeal stimulation in a distributed cortical sensorimotor network in healthy subjects. The proposed paradigm may serve to investigate the effect of neuromodulatory treatments specifically on pharyngeal sensory impairment as relevant cause of neurogenic dysphagia.

Chronic post-stroke oropharyngeal dysphagia is associated with impaired cortical activation to pharyngeal sensory inputs.

The role of afferent sensory pathways in the pathophysiology of post-stroke oropharyngeal dysphagia is not known. We hypothesized that patients with chronic post-stroke dysphagia (PSD) would show impaired sensory cortical activation in the ipsilesional hemisphere. We studied 28 chronic unilateral post-stroke patients [17 PSD and 11 post-stroke non-dysphagic patients (PSnD)] and 11 age-matched healthy volunteers. Event-related sensory-evoked potentials to pharyngeal stimulation (pSEP) and sensory thresholds were assessed. We analyzed pSEP peak latency and amplitude (N1, P1, N2 and P2), and neurotopographic stroke characteristics from brain magnetic resonance imaging. Healthy volunteers presented a highly symmetric bihemispheric cortical pattern of brain activation at centroparietal areas (N1-P1 and N2-P2) to pharyngeal stimuli. In contrast, an asymmetric pattern of reduced ipsilesional activation was found in PSD (N2-P2; P = 0.026) but not in PSnD. PSD presented impaired safety of swallow (penetration-aspiration score: 4.3 ± 1.6), delayed laryngeal vestibule closure (360.0 ± 70.0 ms) and higher National Institute of Health Stroke Scale (7.0 ± 6.2 vs. 1.9 ± 1.4, P = 0.001) and Fazekas scores (3.0 ± 1.4 vs. 2.0 ± 1.1; P < 0.05) than PSnD. pSEP showed a unilateral delay at stroke site exclusively for PSD (peak-latency interhemispheric difference vs. PSnD: N1, 6.5 ± 6.7 vs. 1.1 ± 1.0 ms; N2, 32.0 ± 15.8 vs. 4.5 ± 4.9 ms; P < 0.05). Chronic post-stroke oropharyngeal dysphagia is associated with stroke severity and degree of leukoaraoisis. Impaired conduction and cortical integration of pharyngeal sensory inputs at stroke site are key features of chronic PSD. These findings highlight the role of sensory pathways in the pathophysiology of post-stroke oropharyngeal dysphagia and offer a potential target for future treatments.

The BDNF polymorphism Val66Met may be predictive of swallowing improvement post pharyngeal electrical stimulation in dysphagic stroke patients.

The aim of this study was to explore the effect of brain-derived neurotrophic factor (BDNF) polymorphism rs6265 (Val66Met) in both "natural" and treatment induced recovery of swallowing after dysphagic stroke. Sixteen dysphagic stroke patients that completed a single-blind randomized sham controlled trial of pharyngeal electrical stimulation (PES) within 6weeks of their stroke (N=38), were genotyped for the BDNF SNP Val66Met (rs6265) from saliva samples. These patients received active or sham PES according to randomized allocation. PES was delivered at a set frequency (5Hz), intensity (75% of maximal tolerated), and duration (10minutes) once a day for three consecutive days. Clinical measurements were taken from patients at baseline, 2weeks and 3months post entering the study. Changes in swallowing ability based on the dysphagia severity rating scale (DSRS) were compared between active and sham groups and associated with BDNF SNP status. In the active stimulation group, patients with the Met BDNF allele demonstrated significantly greater improvements in DSRS at 3months compared to patients homozygous for the Val allele (P=.009). By comparison, there were no significant associations at the 2week stage in either the active or sham group, or at 3month in the sham group. Functional scores including the Barthel Index and modified Rankin scale were also unaffected by BDNF status. Our findings suggest an association between BDNF and stimulation induced swallowing recovery. Further work will be required to validate these observations and demonstrate clinical utility in patients.

Pharyngeal stimulus‐induced reflexes are impaired in infants with perinatal asphyxia: Does maturation modify?

Development of pharyngo-esophageal protective reflexes among infants with hypoxic ischemic encephalopathy (HIE) is unclear. Our aim was to distinguish these reflexes from controls and examine the maturational changes in HIE infants. We evaluated 14 HIE infants (seven males) at 41.4±0.6 (HIE Time-1) and 46.5±0.6 (HIE Time-2) weeks postmenstrual age (PMA). Seven controls (three males) were evaluated at 43.5±1.3weeks PMA. Graded pharyngeal stimulation with liquids (0.1, 0.3, 0.5mL in triplicate) concurrent with high-resolution manometry was used to analyze sensory-motor components of pharyngeal reflexive swallowing (PRS), upper esophageal sphincter (UES), contractile reflex (PUCR), and esophageal body characteristics. Linear mixed and generalized estimating equation models were used for comparison among groups. Compared to controls, HIE infants (Time-1 and Time-2) exhibited decreased number of pharyngeal peaks and latency to terminal swallow. HIE Time-1 infants showed increased UES resting tone and distal latency, compared to controls and HIE Time-2. Contractile vigor was increasingly abnormal during maturation, compared to healthy controls. Threshold volumes and frequency distribution of primary responses (PRS: PUCR: None) were not significant among all groups. Compared to controls, HIE infants display significant hypertonicity of skeletal muscle components, impairment of pharyngeal provocation-induced reflexes and smooth muscle contractile vigor, reflecting poor propagation with maturation. These mechanisms may be responsible for inadequate clearance of secretions, ascending refluxate, and oropharyngeal bolus in HIE infants.

Increase of Substance P Concentration in Saliva after Pharyngeal Electrical Stimulation in Severely Dysphagic Stroke Patients – an Indicator of Decannulation Success?

Background/Aims: Substance P (SP) is a neuropeptide, likely acting as a neurotransmitter in the pharyngeal mucosa enhancing the swallow and cough reflex. Pharyngeal Electrical Stimulation (PES) induces a temporary increase of salivary SP levels in healthy adults. Previous evidence suggests that post-stroke dysphagia is related to reduced SP levels. Here, we investigated the effects of PES on SP levels in severely dysphagic stroke patients and a possible link between increase of SP and treatment success. Methods: 23 tracheotomized stroke patients who could not be decannulated due to severe and persisting dysphagia according to endoscopic evaluation received PES for 10 minutes a day over three consecutive days in this prospective single-center study. If initial treatment failed, repetitive stimulation cycles were provided. Saliva samples were collected before and directly after each PES. Results: 61% of participants were decannulated after the first treatment cycle. Increase of SP levels post-stimulation was closely related to treatment success, i.e. decannulation with 79% of successfully treated patients showing increase of SP, whereas 89% of unsuccessfully treated patients had stable or decreased SP levels. Applying logistic regression analysis, increase of SP level remained the only independent predictor of decannulation after PES. All 3 repetitively treated patients showed increased SP levels when progressing from the 1^st to the 2^nd cycle, two of whom were decannulated hereafter. Conclusions: The physiological mechanism of PES may consist in restoration of sensory feedback, which is known to be crucial for the execution of a safe swallow. SP possibly acts as a biomarker for indicating response to PES.

Design and implementation of Pharyngeal electrical Stimulation for early de-cannulation in TRACheotomized (PHAST-TRAC) stroke patients with neurogenic dysphagia: a prospective randomized single-blinded interventional study.

Rationale Ongoing dysphagia in stroke patients weaned from mechanical ventilation often requires long-term tracheotomy to protect the airway from aspiration. In a recently reported single-centre pilot study, a significantly larger proportion (75%) of tracheotomized dysphagic stroke patients regained sufficient control of airway management allowing tracheotomy tube removal (decannulation) 24-72 h after pharyngeal electrical stimulation (PES) compared to controls who received standard therapy over the same time period (20%). Aim To assess the safety and efficacy of PES in accelerating dysphagia rehabilitation and enabling decannulation of tracheotomized stroke patients. Design International multi-centre prospective randomized controlled single-blind trial in approximately 126 ICU patients (the 90th percentile of the calculated maximum sample size). Study outcomes Primary outcome: proportion of stroke patients considered safe for decannulation 24-72 h after PES compared to control patients who do not receive PES. Key secondary outcomes focus on: dysphagia severity, decannulation rates, decannulation rate after a repeat PES treatment in patients persistently dysphagic after an initial PES treatment, stroke severity, duration of ICU-stay, occurrence of adverse events including pneumonia and need for recannulation over 30 days or until hospital discharge (if earlier). Discussion Dysphagia and related airway complications are reported as one of the main reasons for stroke patients remaining tracheotomized once successfully weaned from ventilation. This study will evaluate if PES can improve airway safety sufficiently enough to allow earlier tracheotomy tube removal.

Spatiotemporal characteristics of the pharyngeal event-related potential in healthy subjects and older patients with oropharyngeal dysfunction.

Oropharyngeal dysphagia (OD) is a highly prevalent symptom in older people. Appropriate oropharyngeal sensory feedback is essential for safe and efficient swallowing. However, pharyngeal sensitivity decreases with advancing age and could play a fundamental role in the physiopathology of swallowing dysfunction associated with aging. We aimed to characterize pharyngeal sensitivity and cortical response to a pharyngeal electrical stimulus in healthy volunteers (HV) and older patients with and without OD. Eight young HV, eight older HV without OD, and 14 older patients with OD were studied by electroencephalography through 32 scalp electrodes. Pharyngeal event-related potentials (ERP) were assessed following electrical stimulation of the pharynx. Sensory and tolerance thresholds to the electrical stimulus and latency, amplitude, and scalp current density of each ERP component were analyzed and compared. An ERP source localization study was also performed using the sLORETA software. Older participants (with and without OD) presented an increased sensory threshold to pharyngeal electrical stimulation (10.2±1.7mA and 11.5±1.9mA respectively), compared with young HV (6.0±1.2mA). The cortical activation of older HV in response to pharyngeal electrical stimulus was reduced compared with young HV (N2 amplitude: 0.22±0.79 vs -3.10±0.59, P<.05). Older patients with OD also presented disturbances to the pharyngo-cortical connection together with disrupted pattern of cortical activation. Older people present a decline in pharyngeal sensory function, more severe in older patients with OD. This sensory impairment might be a critical pathophysiological element and a potential target for treatment of swallowing dysfunction in older patients.

Neurorehabilitation strategies for poststroke oropharyngeal dysphagia: from compensation to the recovery of swallowing function.

Oropharyngeal dysphagia (OD) is very prevalent among poststroke patients, causing severe complications but lacking specific neurorehabilitation treatment. This review covers advances in the pathophysiology, diagnosis, and physiologically based neurorehabilitation strategies for poststroke OD. The pathophysiology of oropharyngeal biomechanics can be assessed by videofluoroscopy, as delayed laryngeal vestibule closure is closely associated with aspiration. Stroke may affect afferent or efferent neuronal circuits participating in deglutition. The integrity of oropharyngeal-cortical afferent pathways can be assessed by electroencephalography through sensory-evoked potentials by pharyngeal electrical stimulation, while corticopharyngeal efferent pathways can be characterized by electromyography through motor-evoked potentials by transcranial magnetic stimulation. Dysfunction in both cortico-mediated evoked responses is associated with delayed swallow response and aspiration. Studies have reported hemispherical asymmetry on motor control of swallowing and the relevance of impaired oropharyngeal sensitivity on aspiration. Advances in treatment include improvements in compensatory strategies but are mainly focused on (1) peripheral stimulation strategies and (2) central, noninvasive stimulation strategies with evidence of their clinical benefits. Characterization of poststroke OD is evolving from the assessment of impaired biomechanics to the sensorimotor integration processes involved in deglutition. Treatment is also changing from compensatory strategies to promoting brain plasticity, both to recover swallow function and to improve brain-related swallowing dysfunction.

Pharyngeal Electrical Stimulation in Dysphagia Poststroke

Background. Pharyngeal electrical stimulation (PES) appears to promote cortical plasticity and swallowing recovery poststroke. Objective. We aimed to assess clinical effectiveness with longer follow-up. Methods. Dysphagic patients (n = 36; median = 71 years; 61% male) recruited from 3 trial centers within 6 weeks of stroke, received active or sham PES in a single-blinded randomized design via an intraluminal pharyngeal catheter (10 minutes, for 3days). The primary outcome measure was the Dysphagia Severity Rating (DSR) scale (<4, no-mild; ≥4, moderate-severe). Secondary outcomes included unsafe swallows on the Penetration-Aspiration Scale (PAS ≥ 3), times to hospital discharge, and nasogastric tube (NGT) removal. Data were analyzed using logistic regression. Odds/hazard ratios (ORs/HRs) >1 for DSR <4, hospital discharge, and NGT removal and OR <1 for PAS ≥3, indicated favorable outcomes for active PES. Results. Two weeks post–active PES, 11/18 (61%) had DSR <4: OR (95% CI) = 2.5 (0.52, 14). Effects of active versus sham for secondary outcomes included the following: PAS ≥3 at 2 weeks, OR (95% CI) = 0.61 (0.27, 1.4); times to hospital discharge, 39 days versus 52 days, HR (95% CI) = 1.2 (0.55, 2.5); NGT removal 8 versus 14 days, HR (95% CI) = 2.0 (0.51, 7.9); and DSR <4 at 3 months, OR (95% CI) = 0.97 (0.13, 7.0). PES was well tolerated, without adverse effects or associations with serious complications (chest infections/death). Conclusions. Although the direction of observed differences were consistent with PES accelerating swallowing recovery over the first 2 weeks postintervention, suboptimal recruitment prevents definitive conclusions. Our study design experience and outcome data are essential to inform a definitive, multicenter randomized trial.

Effect comparison of different nursing methods on swallowing function of patients with stroke coma

Objective To explore the effect of pharyngeal chili sauce and cold stimulation on swallowing function of patients with stroke coma. Methods A total of 93 patients with stroke coma were included and randomly divided into three groups. The oral nursing and glossopharyngeal massage were performed in control group (n=30). The oral nursing and cold stimulation were performed in cold stimulation group (n=32). The oral nursing and chili sauce stimulation were performed in chili sauce stimulation group (n=31). The swallowing movement, duration of tracheotomy and incidence of stroke-associated pneumonia were compared among three groups. Results Ten minutes after oral nursing, the swallowing frequency in control group, cold stimulation group and chili sauce stimulation group was (21.09±9.16), (34.16±20.43) and (49.31±25.17), respectively. The difference was statistically significant (F=12.962, P 0.05). Conclusions Both pharyngeal chili sauce and cold stimulation can improve swallowing function of patients with stroke coma. The pharyngeal chili sauce stimulation can stimulate swallowing movement for a longer time to help the recovery of swallowing function, and can shorten the duration of tracheotomy. Key words: Stroke; Swallowing function; Cold stimulation; Chili sauce

PTU-140 Exciting the Human Swallowing Motor System by Combination Stimuli: Effects of Pharyngeal Stimulation and Carbonated Liquids

Introduction Previous reports have revealed that excitation of human pharyngeal motor cortex can be induced by pharyngeal electrical stimulation (PES) 1 and swallowing carbonated water (CW). 2 This study is aimed to investigate whether synchronously combining PES with swallowing (of still water, SW or CW) can potentiate this excitation in pharyngeal cortical area and brainstem. Our hypothesis was that combining inputs would potentiate cortico-pharyngeal excitability compared to each alone which would be more advantageous in the rehabilitation of dysphagic patients. For the evaluation of the excitation in pharyngeal cortex or brainstem, Transcranial or transcutaneous Magnetic Stimulation (TMS) was used to stimulate the corticobulbar and craniobulbar neural networks. Methods Fourteen healthy volunteers (4 females, age range 19–35 yrs) participated and were intubated with an intraluminal catheter for delivering PES and recording pharyngeal electromyography. Each participants underwent the baseline corticobulbar, craniobulbar and hand motor evoked potential (MEP) measurements with TMS. Subjects were then randomised to receive one of four 10 minute interventions (PES only, ShamPES+CW, PES+CW and PES+SW). Corticobulbar, craniobulbar and hand MEPs were then re-measured for up to 60 minutes. Data were analysed using ANOVA and post hoc t-tests. Results Two way rmANOVA comparing pharyngeal MEP amplitude changes in the dominant hemisphere for Interventions×Time showed a significant interaction, F(15, 195) =2.826, P Conclusion Of the interventions applied, only PES alone was able to induce sustained changes in pharyngeal cortical excitability that built up over time. By contrast, combination stimuli were less effective in promoting enhanced cortical excitability. Of interest, combination stimuli did produce short-term increases in excitability in brain stem reflexes. Our data suggest that PES alone may be most advantageous in dysphagic patients who have a difficulty in performing voluntary swallows. References 1 Fraser, et al . Neuron 2002; 34 :831–40. 2 Elshukri, et al . J Appl Physiol 2016 ; 15;120:408–15. Disclosure of Interest None Declared

Pharyngeal Electrical Stimulation for Treatment of Dysphagia in Subacute Stroke: A Randomized Controlled Trial.

Dysphagia is common after stroke, associated with increased death and dependency, and treatment options are limited. Pharyngeal electric stimulation (PES) is a novel treatment for poststroke dysphagia that has shown promise in 3 pilot randomized controlled trials. We randomly assigned 162 patients with a recent ischemic or hemorrhagic stroke and dysphagia, defined as a penetration aspiration score (PAS) of ≥3 on video fluoroscopy, to PES or sham treatment given on 3 consecutive days. The primary outcome was swallowing safety, assessed using the PAS, at 2 weeks. Secondary outcomes included dysphagia severity, function, quality of life, and serious adverse events at 6 and 12 weeks. In randomized patients, the mean age was 74 years, male 58%, ischemic stroke 89%, and PAS 4.8. The mean treatment current was 14.8 (7.9) mA and duration 9.9 (1.2) minutes per session. On the basis of previous data, 45 patients (58.4%) randomized to PES seemed to receive suboptimal stimulation. The PAS at 2 weeks, adjusted for baseline, did not differ between the randomized groups: PES 3.7 (2.0) versus sham 3.6 (1.9), P=0.60. Similarly, the secondary outcomes did not differ, including clinical swallowing and functional outcome. No serious adverse device-related events occurred. In patients with subacute stroke and dysphagia, PES was safe but did not improve dysphagia. Undertreatment of patients receiving PES may have contributed to the neutral result. URL: http://www.controlled-trials.com. Unique identifier: ISRCTN25681641.

Exploring the effects of synchronous pharyngeal electrical stimulation with swallowing carbonated water on cortical excitability in the human pharyngeal motor system.

Previous reports have revealed that excitation of human pharyngeal motor cortex can be induced by pharyngeal electrical stimulation (PES) and swallowing carbonated water (CW). This study investigated whether combining PES with swallowing (of still water, SW or CW) can potentiate this excitation in either cortical and/or brain stem areas assessed with transcranial and transcutaneous magnetic stimulation (TMS). Fourteen healthy volunteers participated and were intubated with an intraluminal catheter to record pharyngeal electromyography and deliver PES. Each participant underwent baseline corticopharyngeal, hand and craniobulbar motor-evoked potential (MEP) measurements. Subjects were then randomized to receive each of four 10-min interventions (PES only, ShamPES+CW, PES+CW, and PES+SW). Corticobulbar, craniobulbar and hand MEPs were then remeasured for up to 60 min and data analyzed using anova and post hoc t-tests. A two-way rmanova for Interventions × Time-point showed a significant corticopharyngeal interaction (p = 0.010). One-way anova with post hoc t-tests indicated significant cortical changes with PES only at 45 (p = 0.038) and 60 min (p = 0.023) and ShamPES+CW immediately (p = 0.008) but not with PES+CW or PES+SW. By contrast, there were immediate craniobulbar amplitude changes only with PES+CW (p = 0.020) which were not sustained. We conclude that only PES produced long-term changes in corticopharyngeal excitability whereas combination stimuli were less effective. Our data suggest that PES alone rather than in combination, may be better for the patients who have difficulty in performing voluntary swallows.

Tu1254 Does Combining Pharyngeal Electrical Stimulation With Simultaneous Swallowing of Carbonated Liquids Enhance the Cortical Swallowing Motor System?

Tu1254 Does Combining Pharyngeal Electrical Stimulation With Simultaneous Swallowing of Carbonated Liquids Enhance the Cortical Swallowing Motor System?

Electrical pharyngeal stimulation increases substance P level in saliva.

Substance P (SP) is a neuropeptide known to enhance the swallow response. It likely acts as a neurotransmitter in the pharyngeal mucosa in response to local stimuli. It has been proposed that dysphagia after stroke may be related to reduced levels of SP, which therefore constitutes a therapeutic target. In the present pilot study, we evaluated whether electrical pharyngeal stimulation (EPS), a neuromodulation device to enhance cortical reorganization for the restoration of swallowing function after brain injury, is able to increase SP in saliva or serum. In a randomized crossover study design, 20 healthy volunteers were treated with 10 min of real (0.2-ms pulses, 5 Hz, 280 V, stimulation intensity (mA) individually adjusted to tolerance level) or sham EPS on two separate sessions. Stimulation was delivered via a pair of bipolar ring electrodes mounted on an intraluminal catheter positioned in the pharynx. Blood and saliva samples were taken prior to, during, and up to 1 h after EPS and analyzed for their SP concentration by ELISA. Following real EPS but not sham stimulation, SP levels in saliva increased immediately and significantly about 28% (p < 0.01) compared to baseline. Serum levels remained unchanged. Electrical pharyngeal stimulation is able to induce pharyngeal SP release in healthy subjects.

Peripheral and central control of swallowing initiation in healthy humans

We investigated (1) how peripheral inputs might assist central inputs in the control of voluntary evoked swallowing, (2) inter-individual variation in involuntary and voluntary swallowing initiation, and (3) whether natural chewing behavior affects the initiation of involuntary swallowing in healthy humans. Eleven participants completed a repetitive saliva swallowing test (RSST), chewing test (CHEW), and rest period (REST). In RSST, participants repetitively swallowed as quickly as possible. In CHEW, subjects chewed gum freely. We delivered pharyngeal electrical stimulation (PEStim) to the laryngopharynx and compared the number of swallows that occurred with and without PEStim. PEStim significantly increased the number of voluntary evoked swallows in RSST, as well as the number of swallows in CHEW and REST trials, although this facilitatory effect was larger in REST trials. We found a positive correlation between the number of swallows at RSST without PEStim and that at REST with PEStim within individuals. Additionally, we found a significant positive correlation between the number of swallows at RSST with PEStim and the sum of that at RSST without PEStim and at REST with PES. Based on the current results, we suggest that (1) peripheral inputs within a certain range appear to facilitate the central inputs that control voluntary swallowing, (2) inter-individual variations in swallowing initiation may arise from differences in the excitability of the common neural network in the lower brainstem, and (3) during chewing, food reduction in the oral cavity is prioritized, such that the neural network associated with chewing may regulate swallowing initiation.