Normal swallowing and functional magnetic resonance imaging: a systematic review

Repetitive Transcranial Magnetic Stimulation on individualized spots based on task fMRI improves swallowing function in post-stroke dysphagia

BACKGROUND

Functional magnetic resonance imaging (fMRI) has not previously been used to localize the swallowing functional area in repetitive transcranial magnetic stimulation (rTMS) treatment for post-stroke dysphagia; Traditionally, the target area for rTMS is the hotspot, which is defined as the specific region of the brain identified as the optimal location for transcranial magnetic stimulation (TMS). This study aims to compare the network differences between the TMS hotspot and the saliva swallowing fMRI activation to determine the better rTMS treatment site and investigate changes in functional connectivity related to post-stroke dysphagia using resting-state fMRI.

METHODS

Using an information-based approach, we conducted a single case study to explore neural functional connectivity in a patient with post-stroke dysphagia before, immediately after rTMS, and four weeks after rTMS intervention. 20 healthy participants underwent fMRI and TMS hotspot localization as a control group. Neural network alterations were assessed , and functional connections related to post-stroke dysphagia were examined using resting-state fMRI.

RESULTS

Compared to the TMS-induced hotspots, the fMRI activation peaks were located significantly more posteriorly and exhibited stronger functional connectivity with bilateral postcentral gyri. Following rTMS treatment, this patient developed functional connection between the brainstem and the bilateral insula, caudate, anterior cingulate cortex, and cerebellum.

CONCLUSION

The saliva swallowing fMRI activation peaks show more intense functional connectivity with bilateral postcentral gyri compared to the TMS hotspots. Activation peak-guided rTMS treatment improves swallowing function in post-stroke dysphagia. This study proposes a novel and potentially more efficacious therapeutic target for rTMS, expanding its therapeutic options for treating post-stroke dysphagia.

The Cortical and Subcortical Neural Control of Swallowing: A Narrative Review

Swallowing is a sophisticated process involving the precise and timely coordination of the central and peripheral nervous systems, along with the musculatures of the oral cavity, pharynx, and airway. The role of the infratentorial neural structure, including the swallowing central pattern generator and cranial nerve nuclei, has been described in greater detail compared with both the cortical and subcortical neural structures. Nonetheless, accumulated data from analysis of swallowing performance in patients with different neurological diseases and conditions, along with results from neurophysiological studies of normal swallowing have gradually enhanced understanding of the role of cortical and subcortical neural structures in swallowing, potentially leading to the development of treatment modalities for patients suffering from dysphagia. This review article summarizes findings about the role of both cortical and subcortical neural structures in swallowing based on results from neurophysiological studies and studies of various neurological diseases. In sum, cortical regions are mainly in charge of initiation and coordination of swallowing after receiving afferent information, while subcortical structures including basal ganglia and thalamus are responsible for movement control and regulation during swallowing through the cortico-basal ganglia-thalamo-cortical loop. This article also presents how cortical and subcortical neural structures interact with each other to generate the swallowing response. In addition, we provided the updated evidence about the clinical applications and efficacy of neuromodulation techniques, including both non-invasive brain stimulation and deep brain stimulation on dysphagia.

Biomechanical and Cortical Control of Tongue Movements During Chewing and Swallowing

Tongue function is vital for chewing and swallowing and lingual dysfunction is often associated with dysphagia. Better treatment of dysphagia depends on a better understanding of hyolingual morphology, biomechanics, and neural control in humans and animal models. Recent research has revealed significant variation among animal models in morphology of the hyoid chain and suprahyoid muscles which may be associated with variation in swallowing mechanisms. The recent deployment of XROMM (X-ray Reconstruction of Moving Morphology) to quantify 3D hyolingual kinematics has revealed new details on flexion and roll of the tongue during chewing in animal models, movements similar to those used by humans. XROMM-based studies of swallowing in macaques have falsified traditional hypotheses of mechanisms of tongue base retraction during swallowing, and literature review suggests that other animal models may employ a diversity of mechanisms of tongue base retraction. There is variation among animal models in distribution of hyolingual proprioceptors but how that might be related to lingual mechanics is unknown. In macaque monkeys, tongue kinematics-shape and movement-are strongly encoded in neural activity in orofacial primary motor cortex, giving optimism for development of brain-machine interfaces for assisting recovery of lingual function after stroke. However, more research on hyolingual biomechanics and control is needed for technologies interfacing the nervous system with the hyolingual apparatus to become a reality.

Dedicated odor-taste stimulation design for fMRI flavor studies

BACKGROUND

Flavor is a mental representation that results from the brain's integration of at least odor and taste, and fMRI can highlight brain-related areas. However, delivering stimuli during fMRI can be challenging especially when administrating liquid stimuli in supine position. It remains unclear how and when odorants are released in the nose and how to improve odorant release.

NEW METHOD

We used a proton transfer reaction mass spectrometer (PTR-MS) to monitor the in vivo release of odorants via the retronasal pathway during retronasal odor-taste stimulation in a supine position. We tested techniques to improve odorant release, including avoiding or delaying swallowing and velum open training (VOT).

RESULTS

Odorant release was observed during retronasal stimulation, before swallowing, and in a supine position. VOT did not improve odorant release. Odorant release during stimulation had a latency more optimal for fitting with BOLD timing than after swallowing.

COMPARISON WITH EXISTING METHOD(S)

Previous in vivo measurements of odorant release under fMRI-like conditions showed that odorant release occurred only after swallowing. On the contrary, a second study found that aroma release could occur before swallowing, but participants were sitting.

CONCLUSION

Our method shows optimal odorant release during the stimulation phase, meeting the criteria for high-quality brain imaging of flavor processing without swallowing-related motion artifacts. These findings provide an important advancement in understanding the mechanisms underlying flavor processing in the brain.

Utility of Dual Monitoring of the Lower Cranial Nerve Motor-Evoked Potentials Threshold Level Criterion to Predict Swallowing Function in Skull Base and Brainstem Surgery

PURPOSE

Evaluate the value of bilateral final/baseline threshold level changes of lower cranial nerve MEPs in postoperative swallowing function deterioration prediction.

METHODS

Bilateral lower cranial nerve motor-evoked potentials (MEPs) were recorded in 51 patients who underwent treatment for skull base and brainstem tumors. Corkscrew-like electrodes were positione 2 cm below C3/C4 and Cz. The MEPs were recorded from different muscle groups, including the posterior pharyngeal wall muscle, tongue muscle, genioglossus muscle, and cricothyroid muscle through paired needle electrodes. Swallowing function was assessed clinically using the Mann Assessment of Swallowing Ability score before and after the procedure at 7 days, 1 month, and 3 months.

RESULTS

Bilateral final/baseline threshold level increases in lower cranial nerve MEPs under the dual monitoring were significantly correlated with postoperative swallowing function deterioration ( r = 0.660 at 7 days, r = 0.735 at 1 month, and r = 0.717 at 3 months; p < 0.05). Bilateral final/baseline threshold level changes of more than 20% were recorded in 23 of the 51 patients, with 21 patients experiencing swallowing function deterioration postoperatively. The other 28 patients had bilateral threshold level changes of less than 20%, with 26 patients maintaining or improving their swallowing function, and 12 of those patients presented transient deterioration of swallowing function in the early postoperative period.

CONCLUSIONS

Dual monitoring of lower cranial nerves and their different muscle groups MEPs was a safe and effective way to predict postoperative swallowing function. An increase in bilateral final/baseline threshold level change of more than 20% was predictive of permanent swallowing deterioration, especially in patients with poor swallowing function preoperatively.

Brain functional activity of swallowing: A meta-analysis of functional magnetic resonance imaging

BACKGROUND

Swallowing is one of the most important activities in our life and serves the dual roles of nutritional intake and eating enjoyment.

OBJECTIVE

The study aimed to conduct a meta-analysis to investigate the brain activity of swallowing.

METHODS

Studies of swallowing using functional magnetic resonance imaging were reviewed in PubMed, Web of Science, China National Knowledge Infrastructure (CNKI), Chinese Science and Technology Periodical Database (VIP) and Wan Fang before 30 November 2021. Two authors analysed the studies for eligibility criteria. The final inclusion of studies was decided by consensus. An activation likelihood estimation (ALE) meta-analysis of these studies was performed with GingerALE, including 16 studies.

RESULTS

For swallowing, clusters with high activation likelihood were found in the bilateral insula, bilateral pre-central gyrus, bilateral post-central gyrus, left transverse temporal gyrus, right medial front gyrus, bilateral inferior frontal gyrus and bilateral cingulate gyrus. For water swallowing, clusters with high activation likelihood were found in the bilateral inferior frontal gyrus and the left pre-central gyrus. For saliva swallowing, clusters with high activation likelihood were found in the bilateral cingulate gyrus, bilateral pre-central gyrus, left post-central gyrus and left transverse gyrus.

CONCLUSION

This meta-analysis reflects that swallowing is regulated by both sensory and motor cortex, and saliva swallowing activates more brain areas than water swallowing, which would promote our knowledge of swallowing and provide some direction for clinical and other research.

Network alterations in eating epilepsy during resting state and during eating using Magnetoencephalography

OBJECTIVE

Eating epilepsy presents various imaging and electrophysiological features along with various seizure triggers. As such, network changes in eating epilepsy have not been comprehensively explored. This study was conducted to illustrate resting state network changes in eating epilepsy and to study the changes in network configurations during eating.

METHODS

Magnetoencephalography recordings of nineteen patients with drug-resistant eating epilepsy were compared with healthy controls during resting state. A subgroup of nine patients and 12 controls had MEG recordings during eating. Network changes were analyzed using phase lag index across 5 frequency bands [delta, theta, alpha, beta, and gamma] using clustering coefficient (CC), betweenness centrality (BC), path length (PL), modularity (Q), and small worldness (SW).

RESULTS

During the resting state, PL was decreased in patients with epilepsy in the delta, theta, and gamma band. Q was lower in patients with epilepsy in the beta and gamma bands. During eating, in patients with epilepsy, PL and SW were increased in all frequency bands, and Q was decreased in the beta band and increased in the rest of the frequency bands. Patients with mixed types of seizures showed higher PL in all bands except alpha, higher Q in all bands, and higher SW in the alpha and beta bands. Node-wise changes in CC and BC implicated changes in DMN and 'eating' networks.

CONCLUSION

Reflex Eating epilepsy presents with a hyperconnected network that exacerbates during eating. The cause of seizure onset and loss of consciousness in eating epilepsy might be due to aberrant network interaction between the regions of the brain involved with eating, such as the sensorimotor cortex, lateral parietal cortex, and insula with the limbic cortex and default mode network across multiple frequency bands.

Electrophysiological Measures of Swallowing Functions: A Systematic Review

The purpose of this systematic review was to examine the application of event-related potentials (ERPs) to investigate neural processes of swallowing functions in adults with and without dysphagia. Computerized literature searches were performed from three search engines. Studies were screened using Covidence (Cochrane tool) and followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement standards (PRISMA-2009). A total of 759 studies were initially retrieved, of which 12 studies met inclusion criteria. Electrophysiological measures assessing swallowing functions were identified in two major ERP categories: (1) sensory potentials and (2) pre-motor potentials. Approximately 80% of eligible studies demonstrated strong methodological quality, although most employed a case series or case-control study design. Pharyngeal sensory-evoked potentials (PSEPs) were used to assess pharyngeal afferent cortical processing. The temporal sequence of the PSEP waveforms varied based on the sensory stimuli. PSEPs were delayed with localized scalp maps in patients with dysphagia as compared to healthy controls. The pre-motor ERPs assessed the cortical substrates involved in motor planning for swallowing, with the following major neural substrates identified: pre-motor cortex, supplementary motor area, and primary sensorimotor cortex. The pre-motor ERPs differed in amplitude for the swallow task (saliva versus liquid swallow), and the neural networks differed for cued versus non-cued task of swallowing suggesting differences in cognitive processes. This systematic review describes the application of electrophysiological measures to assess swallowing function and the promising application for furthering understanding of the neural substrates of swallowing. Standardization of protocols for use of electrophysiological measures to examine swallowing would allow for aggregation of study data to inform clinical practice for dysphagia rehabilitation.

Comprehensive Approaches to Aspiration Pneumonia and Dysphagia in the Elderly on the Disease Time-Axis

Pneumonia in the elderly has been increasing on an annual basis. To a greater or lesser extent, aspiration is a major contributor to the development of pneumonia in the elderly. Antimicrobials alone are not sufficient for the treatment of pneumonia, and the condition may become intractable or even recur repeatedly. In addition, some patients with pneumonia may have no problems with eating, while others are unable to receive the necessary nutrition due to severe dysphagia. It has recently been found that pneumonia decreases both the muscle mass and strength of the swallowing and respiratory muscles, a condition named pneumonia-associated sarcopenia. This contributes to a pathophysiological time-axis of aspiration pneumonia and dysphagia in the elderly, in which silent aspiration leads to the development of pneumonia, and further to dysphagia, malnutrition, and low immunity. Therefore, it is recommended that the treatment and prevention of developing pneumonia should also differ according to an individual’s placement in the disease time-axis. In particular, approaches for preventing aspiration based on scientific findings are able to be implemented at home.

High-Frequency Cerebellar rTMS Improves the Swallowing Function of Patients with Dysphagia after Brainstem Stroke

Objective

To explore the efficacy of high-frequency repetitive transcranial magnetic stimulation (rTMS) of the swallowing motor area of the cerebellum in patients with dysphagia after brainstem stroke.

Methods

A total of 36 patients with dysphagia after brainstem stroke were recruited and divided into 3 groups. Before stimulation, single-pulse transcranial magnetic stimulation (TMS) was used to determine the swallowing dominant cerebellar hemisphere and the representation of the mylohyoid muscle. The three groups of patients received bilateral cerebellar sham stimulation, dominant cerebellar rTMS + contralateral sham stimulation, or bilateral cerebellar rTMS. The stimulus plan for each side was 10 Hz, 80% resting movement threshold (rMT), 250 pulses, 1 s per stimulus, and 9 s intervals. Sham rTMS was performed with the coil held at 90° to the scalp. The changes in the motor evoked potential (MEP) amplitude and the clinical swallowing function scales of the patients after stimulation were compared among the three groups.

Results

34 patients were finally included for statistical analysis. The scores of penetration aspiration scale (PAS) and functional dysphagia scale (FDS) of the patients after 2 weeks of rTMS in the unilateral stimulation group and bilateral stimulation group were better than that in the sham stimulation group, and there was no significant difference between the two groups. The increase in the MEP amplitude of the cerebral hemisphere in the bilateral stimulation group was higher than that in the other two groups, and the increase in the MEP amplitude in the unilateral stimulation group was higher than that in sham stimulation group. There was no correlation between the improvement in patients' clinical swallowing function (PAS scores and FDS scores) and the increase in MEP amplitude in either the unilateral stimulation group or the bilateral stimulation group.

Conclusion

High-frequency rTMS in the cerebellum can improve swallowing function in PSD patients and increase the excitability of the representation of swallowing in the bilateral cerebral hemispheres. Compared with unilateral cerebellar rTMS, bilateral stimulation increased the excitability of the cerebral swallowing cortex more significantly, but there was no significant difference in clinical swallowing function.

Swallowing function in the chronic stage following stroke is associated with white matter integrity of the callosal tract between the interhemispheric S1 swallowing representation areas

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Swallowing performance was tested in dysphagic patients following stroke.

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M1 and S1 callosal tracts relevant for swallowing was mapped in the HCP-dataset.

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S1 and M1 swallowing tracts were overlapping between in house and HCP datasets.

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Swallowing specific callosal tracts showed lower FA for patients compared to HCs.

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Integrity of S1 callosal fibres (FA) was associated with swallowing performance.

Sensorimotor representations of swallowing in pre- and postcentral gyri of both cerebral hemispheres are interconnected by callosal tracts. We were interested in (1) the callosal location of fibers interconnecting the precentral gyri (with the primary motor cortex; M1) and the postcentral gyri (with the primary somatosensory cortex; S1) relevant for swallowing, and (2) the importance of their integrity given the challenges of swallowing compliance after recovery of dysphagia following stroke. We investigated 17 patients who had almost recovered from dysphagia in the chronic stage following stroke and age-matched and gender-matched healthy controls. We assessed their swallowing compliance, investigating swallowing of a predefined bolus in one swallowing movement in response to a ‘go’ signal when in a lying position. A somatotopic representation of swallowing was mapped for the pre- and postcentral gyrus, and callosal tract location between these regions was compared to results for healthy participants. We applied multi-directional diffusion-weighted imaging of the brain in patients and matched controls to calculate fractional anisotropy (FA) as a tract integrity marker for M1/S1 callosal fibers. Firstly, interconnecting callosal tract maps were well spatially separated for M1 and S1, but were overlapped for somatotopic differentiation within M1 and S1 in healthy participants’ data (HCP: head/face representation; in house dataset: fMRI-swallowing representation in healthy volunteers). Secondly, the FA for both callosal tracts, connecting M1 and S1 swallowing representations, were decreased for patients when compared to healthy volunteers. Thirdly, integrity of callosal fibers interconnecting S1 swallowing representation sites was associated with effective swallowing compliance. We conclude that somatosensory interaction between hemispheres is important for effective swallowing in the case of a demanding task undertaken by stroke survivors with good swallowing outcome from dysphagia.

Occurrence of speech-language disorders in the acute phase following pediatric acquired brain injury: results from the Ghent University Hospital

AIMS

This study investigated the occurrence of speech-language disorders during the acute phase of recovery in children with acquired brain injury (ABI) with an age between 0 and 16 years.

METHODS

A retrospective chart analysis was performed including 228 children (n = 118 boys, n = 110 girls) who consecutively presented with ABI over a 10-year period (2006-2016) at the children's rehabilitation center at Ghent University Hospital. Descriptive statistical analyses were applied.

RESULTS

71.1% (162/228) of the children who were admitted to the rehabilitation center presented with a speech-language disorder. Within this sample (n = 162), results demonstrated the occurrence of acquired disorders in language (48.9%), speech (35.1%), learning (33.3%), swallowing (21.5%), and early communicative functions (17.4%). The proportion of children presenting with disturbances in early communicative functions differed by ABI cause. More than half (10/18, 58.8%) of the children who presented with ABI following inflammatory processes demonstrated disorders in early communicative functions.

CONCLUSIONS

Especially in young children who present with inflammatory processes as the ABI cause, speech-language pathologists (SLPs) must be aware of disorders in early speech-language development. The present findings allow the SLP to appropriately plan research, education, and clinical management.

Medical aromatherapy in geriatric syndrome

Geriatric syndromes are symptoms and signs, such as falls, incontinence, delirium, pressure ulcers, dysphagia and so on, that often threaten the independence of older adults, rather than the disease itself. Although the syndromes are very common in older people, it is difficult to treat those by modern medicine due to their complexity. To mitigate the intractable geriatric symptoms, we review the efficacy of aromatherapy, especially for dysphagia, dyspnea, cognitive dysfunction and falls in geriatric syndrome. Olfactory stimulation using a volatile black pepper oil on institutional residents improved the swallowing reflex, which is a crucial risk factor of aspiration pneumonia. Brain imaging study showed that olfactory stimulation using volatile black pepper oil activated cerebral regions of the anterior cingulate and the insular cortex, which play a role in controlling appetite and swallowing. Also, aromatherapy with volatile l-menthol decreased the sense of dyspnea and improved the efficacy of exercise therapy. The fragrance of the combination of rosemary and lemon oils in the morning, and the combination of lavender and orange oils in the night-time were reported to improve cognition and behavioural and psychological symptoms of dementia, respectively. Also, the combination of lavender and lemon balm oils was reported to be effective for irritability-related agitation in older adults. Furthermore, aromatherapy with lavender fragrance could improve both static and dynamic balance, resulting in a reduction in the number of fallers and the incidence rate in older people. Thus, aromatherapy is a promising remedy for geriatric syndrome. Geriatr Gerontol Int 2021; 21: 377-385.

A Novel Method for Triggering the Swallowing Reflex in Patients with Amyotrophic Lateral Sclerosis: the Ishizaki Press Method

This study describes the identification of specific maxillofacial points triggering the swallowing reflex by finger pressure in a patient with severe amyotrophic lateral sclerosis. This method has been named as the "Ishizaki Press Method." The first point was identified in a serendipitous encounter during training sessions to aid communication. This led to the search for such additional points, after obtaining informed consent from the patient and his relatives. Seven effective points were identified: the depressions in front of the left and right tragus (Ting gong points), bilateral points over the parotid and submandibular glands, and a point over the mentum in the midline of the face. The efficacy of these trigger points was noted to be ≥ 70%. The mean time taken for swallowing to occur in response to the stimulation at each of these points was less than 10 s, and the induction of a rapid swallowing reflex was recognized. Alternating left and right stimulations of the Ting gong points and the parotid points triggered the swallowing reflex significantly faster than unilateral stimulations alone. The Ishizaki Press Method may improve the management of dysphagia in patients with amyotrophic lateral sclerosis.

Effects of aging on brain networks during swallowing: general linear model and independent component analyses

Swallowing disorders occur more frequently in older adults. However, the effects of the aging process on neural activation when swallowing are unclear. We aimed to identify neural regions activated during swallowing and evaluate changes in neural activation and neural networks with aging. Using a general linear model (GLM) and independent component (IC) analyses, blood oxygen level-dependent (BOLD) signals were observed in the lateral precentral gyrus, postcentral gyrus, anterior insular cortices, supramarginal gyri, and medial frontal gyrus during swallowing. The right thalamus and anterior cingulate gyri were found to be active areas by GLM and IC analyses, respectively. In the correlational analyses, age was negatively correlated with BOLD signals of the lateral precentral gyri, postcentral gyri, and insular cortices in swallowing tasks. Additionally, correlation analyses between ICs of all participants and age revealed negative correlations in the right supramarginal gyrus, both anterior cingulate cortices, putamen, and cerebellum. In the network analysis, the BOLD signal positively correlated with age in the default mode network (DMN), and was negatively correlated in the lateral precentral gyri, postcentral gyri, and insular cortices. The amplitude of low-frequency fluctuations was significantly decreased in the DMN and increased in swallowing-related areas during swallowing tasks. These results suggest that aging has negative effects on the activation of swallowing-related regions and task-induced deactivation of the DMN. These changes may be used to detect early functional decline during swallowing.

Regional brain responses associated with using imagination to evoke and satiate thirst

In response to dehydration, humans experience thirst. This subjective state is fundamental to survival as it motivates drinking, which subsequently corrects the fluid deficit. To elicit thirst, previous studies have manipulated blood chemistry to produce a physiological thirst stimulus. In the present study, we investigated whether a physiological stimulus is indeed required for thirst to be experienced. Functional MRI (fMRI) was used to scan fully hydrated participants while they imagined a state of intense thirst and while they imagined drinking to satiate thirst. Subjective ratings of thirst were significantly higher for imagining thirst compared with imagining drinking or baseline, revealing a successful dissociation of thirst from underlying physiology. The imagine thirst condition activated brain regions similar to those reported in previous studies of physiologically evoked thirst, including the anterior midcingulate cortex (aMCC), anterior insula, precentral gyrus, inferior frontal gyrus, middle frontal gyrus, and operculum, indicating a similar neural network underlies both imagined thirst and physiologically evoked thirst. Analogous brain regions were also activated during imagined drinking, suggesting the neural representation of thirst contains a drinking-related component. Finally, the aMCC showed an increase in functional connectivity with the insula during imagined thirst relative to imagined drinking, implying functional connectivity between these two regions is needed before thirst can be experienced. As a result of these findings, this study provides important insight into how the neural representation of subjective thirst is generated and how it subsequently motivates drinking behavior.

Effects of Motor Imagery and Visual Neurofeedback on Activation in the Swallowing Network: A Real-Time fMRI Study

Motor imagery of movements is used as mental strategy in neurofeedback applications to gain voluntary control over activity in motor areas of the brain. In the present functional magnetic resonance imaging (fMRI) study, we first addressed the question whether motor imagery and execution of swallowing activate comparable brain areas, which has been already proven for hand and foot movements. Prior near-infrared spectroscopy (NIRS) studies provide evidence that this is the case in the outer layer of the cortex. With the present fMRI study, we want to expand these prior NIRS findings to the whole brain. Second, we used motor imagery of swallowing as mental strategy during visual neurofeedback to investigate whether one can learn to modulate voluntarily activity in brain regions, which are associated with active swallowing, using real-time fMRI. Eleven healthy adults performed one offline session, in which they executed swallowing movements and imagined swallowing on command during fMRI scanning. Based on this functional localizer task, we identified brain areas active during both tasks and defined individually regions for feedback. During the second session, participants performed two real-time fMRI neurofeedback runs (each run comprised 10 motor imagery trials), in which they should increase voluntarily the activity in the left precentral gyrus by means of motor imagery of swallowing while receiving visual feedback (the visual feedback depicted one's own fMRI signal changes in real-time). Motor execution and imagery of swallowing activated a comparable network of brain areas including the bilateral pre- and postcentral gyrus, inferior frontal gyrus, basal ganglia, insula, SMA, and the cerebellum compared to a resting condition. During neurofeedback training, participants were able to increase the activity in the feedback region (left lateral precentral gyrus) but also in other brain regions, which are generally active during swallowing, compared to the motor imagery offline task. Our results indicate that motor imagery of swallowing is an adequate mental strategy to activate the swallowing network of the whole brain, which might be useful for future treatments of swallowing disorders.

The Initiation of Swallowing Can Indicate the Prognosis of Disorders of Consciousness: A Self-Controlled Study

Objective: To detect the initiation of swallowing in patients with disorders of consciousness (DOC) as well as the relationship between the initiation of swallowing and the prognosis of DOC patients. Methods: Nineteen DOC patients were included in this study, and a self-controlled trial compared five different stimuli. The five different stimuli were as follows: (1) one command, as recommended by the Coma Recovery Scale-Revised (CRS-R), which was "open your mouth"; (2) placing a spoon in front of the patient's mouth without a command; (3) placing a spoon filled with water in front of the patient's mouth without a command; (4) one command-"there is a spoon; open your mouth"-with a spoon in front of the patient's mouth; (5) one command, "there is a spoon with water; open your mouth," with a spoon filled with water in front of the patient's mouth. All 19 patients were given these five stimuli randomly, and any one of the commands was presented four times to a patient, one at a time, at 15-s intervals. The sensitivity and specificity of the initiation of swallowing in detecting conscious awareness were determined. Results: None of the patients responded to the first four stimuli. However, six patients showed initiated swallowing toward the fifth stimulus. Among those six, five patients showed improvement in their consciousness state 6 months later. The sensitivity and specificity of the initiation of swallowing for DOC patients was 83.33% [95% CIs (36%, 100%)] and 92.31% [95% CIs (64%, 100%)], respectively. Conclusions: The initiation of swallowing can be an early indication of conscious behavior and can likely provide evidence of conscious awareness. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT03508336; Date of registration: 2018/4/16.

Functional Characterization of the Human Speech Articulation Network

A number of brain regions have been implicated in articulation, but their precise computations remain debated. Using functional magnetic resonance imaging, we examine the degree of functional specificity of articulation-responsive brain regions to constrain hypotheses about their contributions to speech production. We find that articulation-responsive regions (1) are sensitive to articulatory complexity, but (2) are largely nonoverlapping with nearby domain-general regions that support diverse goal-directed behaviors. Furthermore, premotor articulation regions show selectivity for speech production over some related tasks (respiration control), but not others (nonspeech oral-motor [NSO] movements). This overlap between speech and nonspeech movements concords with electrocorticographic evidence that these regions encode articulators and their states, and with patient evidence whereby articulatory deficits are often accompanied by oral-motor deficits. In contrast, the superior temporal regions show strong selectivity for articulation relative to nonspeech movements, suggesting that these regions play a specific role in speech planning/production. Finally, articulation-responsive portions of posterior inferior frontal gyrus show some selectivity for articulation, in line with the hypothesis that this region prepares an articulatory code that is passed to the premotor cortex. Taken together, these results inform the architecture of the human articulation system.

Relationship between pharyngeal response time and lateralized brain lesion in stroke

Objectives: To analyze the relationship between pharyngeal response time (PRT) and lateralization of brain lesions. Methods: A Cross-sectional study. 73 videofluoroscopic swallow studies (VFSS)were conducted on patients after stroke The study subjects were divided into : group 1 (G1) consisting of 39 individuals with left cortical lesion and group 2 (G2) consisting of 34 individuals with right cortical lesions. The VFSS of G1 and G2 subjects were analyzed using puree (A) and liquid (B) consistencies, and  were also subdivided into young adults and older persons. . The mean PRT was divided into times shorter and longer than 250 ms. Results: No statistically significant difference was observed between G1 and G2 for the A and B consistencies, being obtained : G1 (A mean: 56.6 ms; B mean: 99.5 ms; A mean: 3627 ms; B mean: 1712 ms) and G2 (A mean: 79.6 ms; B mean: 110.7 ms; A mean: 2040 ms, B mean: 1529 ms), for PRT shorter (A:p = .673; B: p = 1.000) and longer (A: p = .435; B: p = .847) than 250 ms, respectively. No statistically significant difference was found regarding the variable age in the comparison between young and old adults for mean PRT according to the A and B consistencies in G1 (A: p = .260; B: p = .732) and G2 (A: p = .586; B: p = .104). Conclusion: No relationship between PRT and lateralization of brain lesion was observed with respect to subject age and to the swallowing of different food consistencies.

Factors Influencing Oral Intake Improvement and Feeding Tube Dependency in Patients with Poststroke Dysphagia

OBJECTIVE

To assess ischemic stroke patients regarding the relationship between lesion locations, swallowing impairment, medical and demographic factors and (1) oral intake improvement and (2) feeding tube dependency at discharge from their acute hospital stay.

METHODS

We conducted an exploratory, retrospective observational longitudinal cohort study of acute, first-ever, ischemic stroke patients. Patients who had an initial nonoral feeding recommendation from a speech and language pathologist and who underwent a modified barium swallow study within their hospital stay were included. Oral intake status was measured with the Functional Oral Intake Scale (FOIS) as the change in FOIS during the hospital stay and as feeding tube dependency at hospital discharge. Associations were assessed with multiple linear regression modeling controlling for age, comorbidities, and hospital length of stay.

RESULTS

We included 44 stroke patients. At hospital discharge, 93% of patients had oral intake restrictions and 30% were feeding tube dependent. Following multiple linear regression modeling, age, damage to the left superior frontal gyrus, dorsal anterior cingulate gyrus, hypothalamus, and nucleus accumbens were significant predictors for FOIS change. Feeding tube dependency showed no significant associations with any prognostic variables when controlling for confounders.

CONCLUSIONS

The vast majority of patients with an initial nonoral feeding recommendation are discharged with oral intake restrictions indicating a continued need for swallowing assessments and treatment after discharge. Lesion locations associated with motivation, reward, and drive to consume food as well as swallowing impairment, higher age, and more comorbidities were related to less oral intake improvement.

The After-Effects of Theta Burst Stimulation Over the Cortex of the Suprahyoid Muscle on Regional Homogeneity in Healthy Subjects

Theta burst stimulation (TBS) is a powerful variant of repetitive transcranial magnetic stimulation (rTMS), making it potentially useful for the treatment of swallowing disorders. However, how dose TBS modulate human swallowing cortical excitability remains unclear. Here, we aim to measure the after-effects of spontaneous brain activity at resting-state using the regional homogeneity (ReHo) approach in healthy subjects who underwent different TBS protocols over the suprahyoid muscle cortex. Sixty healthy subjects (23.45 ± 2.73 years, 30 males) were randomized into three groups which completed different TBS protocols. The TMS coil was applied over the cortex of the suprahyoid muscles. Data of resting-state functional MRI (Rs-fMRI) of the subjects were acquired before and after TBS. The ReHo was compared across sessions [continuous TBS (cTBS), intermittent TBS (iTBS) and cTBS/iTBS] and runs (pre/post TBS). In the comparison between pre- and post-TBS, increased ReHo was observed in the right lingual gyrus and right precuneus and decreased ReHo in the left cingulate gyrus in the cTBS group. In the iTBS group, increased ReHo values were seen in the pre-/postcentral gyrus and cuneus, and decreased ReHo was observed in the left cerebellum, brainstem, bilateral temporal gyrus, insula and left inferior frontal gyrus. In the cTBS/iTBS group, increased ReHo was found in the precuneus and decreased ReHo in the right cerebellum posterior lobe, left anterior cerebellum lobe, and right inferior frontal gyrus. In the post-TBS inter-groups comparison, increased ReHo was seen in right middle occipital gyrus and decreased ReHo in right middle frontal gyrus and right postcentral gyrus (cTBS vs. cTBS/iTBS). Increased ReHo was shown in left inferior parietal lobule and left middle frontal gyrus (cTBS vs. iTBS). Increased ReHo was shown in right medial superior frontal gyrus and decreased ReHo in right cuneus (cTBS/iTBS vs. iTBS). Our findings indicate cTBS had no significant influence on ReHo in the primary sensorimotor cortex, iTBS facilitates an increased ReHo in the bilateral sensorimotor cortex and a decreased ReHo in multiple subcortical areas, and no reverse effect exhibits when iTBS followed the contralateral cTBS over the suprahyoid motor cortex. The results provide a novel insight into the neural mechanisms of TBS on swallowing cortex.

Pink1 -/- Rats Show Early-Onset Swallowing Deficits and Correlative Brainstem Pathology

Parkinson disease (PD) compromises oropharyngeal swallowing, which negatively affects quality of life and contributes to aspiration pneumonia. Dysphagia often begins early in the disease process, and does not improve with standard therapies. As a result, swallowing deficits are undertreated in the PD population. The Pink1 -/- rat is used to model PD, and demonstrates widespread brainstem neuropathology in combination with early-onset sensorimotor dysfunction; however, to date, swallowing behaviors have not been evaluated. To test the hypothesis that Pink1 -/- rats demonstrate early-onset differences in swallowing, we analyzed within-subject oropharyngeal swallowing using videofluoroscopy. Pink1 -/- and wildtype (WT) controls at 4 (Pink1 -/- n = 16, WT = 16) and 8 (Pink1 -/- n = 12, WT = 12) months of age were tested. The average and maximum bolus size was significantly increased in Pink1 -/- rats at both 4 and 8 months. Bolus average velocity was increased at 8 months for all animals; yet, Pink1 -/- animals had significantly increased velocities compared to WT at 8 months. The data show a significant reduction in mastication rate for Pink1 -/- rats at 8 months suggesting the onset of oromotor dysfunction begins at this time point. Relationships among swallowing variables and neuropathological findings, such as increased alpha-synuclein protein in the nucleus ambiguus and reductions in noradrenergic cells in the locus coeruleus in the Pink1 -/- rats, were determined. The presence of early oropharyngeal swallowing deficits and relationships to brainstem pathology in Pink1-/- rat models of PD indicate that this may be a useful model of early swallowing deficits and their mechanisms. These findings suggest clinical implications for early detection and management of dysphagia in PD.

Effect of peripherally and cortically evoked swallows on jaw reflex responses in anesthetized rabbits

This study aimed to investigate whether the jaw-opening (JOR) and jaw-closing reflexes (JCR) are modulated during not only peripherally, but also centrally, evoked swallowing. Experiments were carried out on 24 adult male Japanese white rabbits. JORs were evoked by trigeminal stimulation at 1 Hz for 30 s. In the middle 10 s, either the superior laryngeal nerve (SLN) or cortical swallowing area (Cx) was simultaneously stimulated to evoke swallowing. The peak-to-peak JOR amplitude was reduced during the middle and late 10-s periods (i.e., during and after SLN or Cx stimulation), and the reduction was dependent on the current intensity of SLN/Cx stimulation: greater SLN/Cx stimulus current resulted in greater JOR inhibition. The reduction rate was significantly greater during Cx stimulation than during SLN stimulation. The amplitude returned to baseline 2 min after 10-s SLN/Cx stimulation. The effect of co-stimulation of SLN and Cx was significantly greater than that of SLN stimulation alone. There were no significant differences in any parameters of the JCR between conditions. These results clearly showed that JOR responses were significantly suppressed, not only during peripherally evoked swallowing but also during centrally evoked swallowing, and that the inhibitory effect is likely to be larger during centrally compared with peripherally evoked swallowing. The functional implications of these results are discussed.

Influence of anterior midcingulate cortex on drinking behavior during thirst and following satiation

This study provides important insight into how the human brain regulates fluid intake in response to changes in hydration status. The findings presented here reveal that activity in the anterior midcingulate cortex (aMCC) is associated with drinking responses during a state of thirst, and that this region is likely to contribute to the facilitation of drinking during this state. These results are consistent with a reduction in the influence of the aMCC contributing to the conclusion of drinking during a state of satiation. Because drinking stops before changes in blood volume and chemistry signal the restoration of fluid balance, these results implicate the aMCC in the regulation of drinking behavior before these changes manifest within the circulatory system.

In humans, activity in the anterior midcingulate cortex (aMCC) is associated with both subjective thirst and swallowing. This region is therefore likely to play a prominent role in the regulation of drinking in response to dehydration. Using functional MRI, we investigated this possibility during a period of “drinking behavior” represented by a conjunction of preswallow and swallowing events. These events were examined in the context of a thirsty condition and an “oversated” condition, the latter induced by compliant ingestion of excess fluid. Brain regions associated with swallowing showed increased activity for drinking behavior in the thirsty condition relative to the oversated condition. These regions included the cingulate cortex, premotor areas, primary sensorimotor cortices, the parietal operculum, and the supplementary motor area. Psychophysical interaction analyses revealed increased functional connectivity between the same regions and the aMCC during drinking behavior in the thirsty condition. Functional connectivity during drinking behavior was also greater for the thirsty condition relative to the oversated condition between the aMCC and two subcortical regions, the cerebellum and the rostroventral medulla, the latter containing nuclei responsible for the swallowing reflex. Finally, during drinking behavior in the oversated condition, ratings of swallowing effort showed a negative association with functional connectivity between the aMCC and two cortical regions, the sensorimotor cortex and the supramarginal gyrus. The results of this study provide evidence that the aMCC helps facilitate swallowing during a state of thirst and is therefore likely to contribute to the regulation of drinking after dehydration.

Hemodynamic signal changes during saliva and water swallowing: a near-infrared spectroscopy study

Here, we compared the hemodynamic response observed during swallowing of water or saliva using near-infrared spectroscopy (NIRS). Sixteen healthy adults swallowed water or saliva in a randomized order. Relative concentration changes in oxygenated and deoxygenated hemoglobin during swallowing were assessed. Both swallowing tasks led to the strongest NIRS signal change over the bilateral inferior frontal gyrus. Water swallowing led to a stronger activation over the right hemisphere while the activation focus for saliva swallowing was stronger left lateralized. The NIRS time course also differed between both swallowing tasks especially at the beginning of the tasks, which might be a sign of differences in task effort. Our results show that NIRS is a sensitive measure to reveal differences in the topographical distribution and time course of the hemodynamic response between distinct swallowing tasks and might be therefore an adequate diagnostic and therapy tool for swallowing difficulties.

Functional changes of neural circuits in stroke patients with dysphagia: A meta-analysis

OBJECTIVE

Dysphagia is a common problem in stroke patients with unclear pathogenesis. Several recent functional magnetic resonance imaging (fMRI) studies had been carried out to explore the cerebral functional changes in dysphagic stroke patients. The aim of this study was to analysis these imaging findings using a meta-analysis.

METHODS

We used seed-based d mapping (SDM) to conduct a meta-analysis for dysphagic stroke patients prior to any kind of special treatment for dysphagia. A systematic search was conducted for the relevant studies. SDM meta-analysis method was used to examine regions of increased and decreased functional activation between dysphagic stroke patients and healthy controls.

RESULTS

Finally, six studies including 81 stroke patients with dysphagia and 78 healthy controls met the inclusion standards. When compared with healthy controls, stroke patients with dysphagia showed hyperactivation in left cingulate gyrus, left precentral gyrus and right posterior cingulate gyrus, and hypoactivation in right cuneus and left middle frontal gyrus.

CONCLUSIONS

The hyperactivity of precentral gyrus is crucial in stroke patients with dysphagia and may be associated with the severity of stroke. Besides the motor areas, the default-mode network regions (DMN) and affective network regions (AN) circuits are also involved in dysphagia after stroke.

Overdrinking, swallowing inhibition, and regional brain responses prior to swallowing

In humans, drinking replenishes fluid loss and satiates the sensation of thirst that accompanies dehydration. Typically, the volume of water drunk in response to thirst matches the deficit. Exactly how this accurate metering is achieved is unknown; recent evidence implicates swallowing inhibition as a potential factor. Using fMRI, this study investigated whether swallowing inhibition is present after more water has been drunk than is necessary to restore fluid balance within the body. This proposal was tested using ratings of swallowing effort and measuring regional brain responses as participants prepared to swallow small volumes of liquid while they were thirsty and after they had overdrunk. Effort ratings provided unequivocal support for swallowing inhibition, with a threefold increase in effort after overdrinking, whereas addition of 8% (wt/vol) sucrose to water had minimal effect on effort before or after overdrinking. Regional brain responses when participants prepared to swallow showed increases in the motor cortex, prefrontal cortices, posterior parietal cortex, striatum, and thalamus after overdrinking, relative to thirst. Ratings of swallowing effort were correlated with activity in the right prefrontal cortex and pontine regions in the brainstem; no brain regions showed correlated activity with pleasantness ratings. These findings are all consistent with the presence of swallowing inhibition after excess water has been drunk. We conclude that swallowing inhibition is an important mechanism in the overall regulation of fluid intake in humans.

A human model of restricted upper esophageal sphincter opening and its pharyngeal and UES deglutitive pressure phenomena

Oropharyngeal dysphagia due to upper esophageal sphincter (UES) dysfunction is commonly encountered in the clinical setting. Selective experimental perturbation of various components of the deglutitive apparatus can provide an opportunity to improve our understanding of the swallowing physiology and pathophysiology. The aim is to characterize the pharyngeal and UES deglutitive pressure phenomena in an experimentally induced restriction of UES opening in humans. We studied 14 volunteers without any dysphagic symptoms (7 men, 66 ± 11 yr) but with various supraesophageal reflux symptoms. To induce UES restriction, we used a handmade device that with adjustment could selectively apply 0, 20, 30, or 40 mmHg pressure perpendicularly to the cricoid cartilage. Deglutitive pharyngeal and UES pressure phenomena were determined during dry and 5- and 10-ml water swallows × 3 for each of the UES perturbations. External cricoid pressure against the UES resulted in a significant increase in hypopharyngeal intrabolus pressure and UES nadir deglutitive relaxation pressure for all tested swallowed volumes (P < 0.05). Application of external cricoid pressure increased the length of the UES high pressure zone from 2.5 ± 0.2 to 3.1 ± 0.2, 3.5 ± 0.1, and 3.7 ± 0.1 cm for 20, 30, and 40 mmHg cricoid pressure, respectively (P < 0.05). External cricoid pressure had no significant effect on pharyngeal peristalsis. On the other hand, irrespective of external cricoid pressure deglutitive velopharyngeal contractile integral progressively increased with increased swallowed volumes (P < 0.05). In conclusion, acute experimental restriction of UES opening by external cricoid pressure manifests the pressure characteristics of increased resistance to UES transsphincteric flow observed clinically without affecting the pharyngeal peristaltic contractile function.

Position paper of the German Society of Oto-Rhino-Laryngology, Head and Neck Surgery and the German Society of Phoniatrics and Pediatric Audiology - Current state of clinical and endoscopic diagnostics, evaluation, and therapy of swallowing disorders in children

Swallowing disorders are frequent. The main concern is mortality due to aspiration-induced pneumonia and malnutrition. In addition, quality of life is severely affected. The demographic trend indicates an increase of dysphagia in the future. Neurodegenerative diseases, tumors of the digestive tract, and sequelae of tumor treatment in the head and neck region are the main pathologic entities.

Predominantly ENT physicians and phoniatricians are asked for diagnostics and therapy, and will coordinate the interdisciplinary treatment according to the endoscopic findings.

A differentiated approach in history, diagnostics, and symptom-oriented treatment is necessary for these mostly complex disorders. Integration of non-medical staff such as speech therapists, physiotherapists, and occupational therapists in planning and executing an effective therapy expands and completes the patient-oriented care. Conservative treatment by these therapists is an important pillar in the treatment. Parts of the specific diagnostics can be taken over in close cooperation.

In particular, an interdisciplinary cooperation with the staff of intensive care medicine is essential.

The diagnostic procedures of specific endoscopy as described in this position paper are part of the primary and fundamental tasks of ENT specialists and phoniatrists.

Endoscopy is a medical service that is basically not delegable. Consequently, substitution of the physician is excluded.

Voluntary Modulation of Hemodynamic Responses in Swallowing Related Motor Areas: A Near-Infrared Spectroscopy-Based Neurofeedback Study

In the present study, we show for the first time that motor imagery of swallowing, which is defined as the mental imagination of a specific motor act without overt movements by muscular activity, can be successfully used as mental strategy in a neurofeedback training paradigm. Furthermore, we demonstrate its effects on cortical correlates of swallowing function. Therefore, N = 20 healthy young adults were trained to voluntarily increase their hemodynamic response in swallowing related brain areas as assessed with near-infrared spectroscopy (NIRS). During seven training sessions, participants received either feedback of concentration changes in oxygenated hemoglobin (oxy-Hb group, N = 10) or deoxygenated hemoglobin (deoxy-Hb group, N = 10) over the inferior frontal gyrus (IFG) during motor imagery of swallowing. Before and after the training, we assessed cortical activation patterns during motor execution and imagery of swallowing. The deoxy-Hb group was able to voluntarily increase deoxy-Hb over the IFG during imagery of swallowing. Furthermore, swallowing related cortical activation patterns were more pronounced during motor execution and imagery after the training compared to the pre-test, indicating cortical reorganization due to neurofeedback training. The oxy-Hb group could neither control oxy-Hb during neurofeedback training nor showed any cortical changes. Hence, successful modulation of deoxy-Hb over swallowing related brain areas led to cortical reorganization and might be useful for future treatments of swallowing dysfunction.

The perturbation paradigm modulates error-based learning in a highly automated task: outcomes in swallowing kinematics

Traditional motor learning studies focus on highly goal-oriented, volitional tasks that often do not readily generalize to real-world movements. The goal of this study was to investigate how different perturbation paradigms alter error-based learning outcomes in a highly automated task. Swallowing was perturbed with neck surface electrical stimulation that opposes hyo-laryngeal elevation in 25 healthy adults (30 swallows: 10 preperturbation, 10 perturbation, and 10 postperturbation). The four study conditions were gradual-masked, gradual-unmasked, abrupt-masked, and abrupt-unmasked. Gradual perturbations increasingly intensified overtime, while abrupt perturbations were sustained at the same high intensity. The masked conditions reduced cues about the presence/absence of the perturbation (pre- and postperturbation periods had low stimulation), but unmasked conditions did not (pre- and postperturbation periods had no stimulation). Only hyo-laryngeal range of motion measures had significant outcomes; no timing measure demonstrated learning. Systematic-error reduction occurred only during the abrupt-masked and abrupt-unmasked perturbations. Only the abrupt-masked perturbation caused aftereffects. In this highly automated task, gradual perturbations did not induce learning similarly to findings of some volitional, goal-oriented adaptation task studies. Furthermore, our subtle and brief adjustment of the stimulation paradigm (masked vs. unmasked) determined whether aftereffects were present. This suggests that, in the unmasked group, sensory predictions of a motor plan were quickly and efficiently modified to disengage error-based learning behaviors.

Electrophysiological Techniques to Evaluate Swallowing in Central and Peripheral Nervous System Disorders

Neurogenic dysphagia is a frequent condition that may result in serious complications. Despite high incidence of neurogenic dysphagia, the neurologist is not really interested in its clinical diagnosis and management. In this review, several neurophysiological methods are described to evaluate the neurogenic dysphagia. These kinds of assessment methods are important for early diagnosis and some management strategies against to progressive swallowing pathology. The longitudinal follow-up of the patients also provides data about the prognosis of dysphagia. In our opinion, the neurophysiological methods presented in this review are reliable, cheap, and easy applicable quantitative tests to detect and follow both clinical and subclinical dysphagia. All these electrophysiological techniques can be applied within the discipline of the EMG laboratory.

Hemodynamic Signal Changes Accompanying Execution and Imagery of Swallowing in Patients with Dysphagia: A Multiple Single-Case Near-Infrared Spectroscopy Study

In the present multiple case study, we examined hemodynamic changes in the brain in response to motor execution (ME) and motor imagery (MI) of swallowing in dysphagia patients compared to healthy matched controls using near-infrared spectroscopy (NIRS). Two stroke patients with cerebral lesions in the right hemisphere, two stroke patients with lesions in the brainstem, and two neurologically healthy control subjects actively swallowed saliva (ME) and mentally imagined to swallow saliva (MI) in a randomized order while changes in concentration of oxygenated hemoglobin (oxy-Hb) and deoxygenated hemoglobin (deoxy-Hb) were assessed. In line with recent findings in healthy young adults, MI and ME of swallowing led to the strongest NIRS signal change in the inferior frontal gyrus in stroke patients as well as in healthy elderly. We found differences in the topographical distribution and time course of the hemodynamic response in dependence on lesion location. Dysphagia patients with lesions in the brainstem showed bilateral hemodynamic signal changes in the inferior frontal gyrus during active swallowing comparable to healthy controls. In contrast, dysphagia patients with cerebral lesions in the right hemisphere showed more unilateral activation patterns during swallowing. Furthermore, patients with cerebral lesions showed a prolonged time course of the hemodynamic response during MI and ME of swallowing compared to healthy controls and patients with brainstem lesions. Brain activation patterns associated with ME and MI of swallowing were largely comparable, especially for changes in deoxy-Hb. Hence, the present results provide new evidence regarding timing and topographical distribution of the hemodynamic response during ME and MI of swallowing in dysphagia patients and may have practical impact on future dysphagia treatment.

[Position paper of the German Society of Oto-Rhino-Laryngology, Head and Neck Surgery and the German Society of Phoniatrics and Pediatric Audiology - current state of clinical and endoscopic diagnostics, evaluation, and therapy of swallowing disorders in children and adults]

Position Paper of the German Society of Oto-Rhino-Laryngology, Head and Neck Surgery and the German Society of Phoniatrics and Pediatric Audiology - Current State of Clinical and Endoscopic Diagnostics, Evaluation, and Therapy of Swallowing Disorders in Children and AdultsSwallowing disorders are frequent. The main concern is mortality due to aspiration induced pneumonia and malnutrition. On the other hand quality of life is severely affected. The demographic trend indicates an increase of dysphagia in the future. Neurodegenerative diseases, tumors of the digestive tract and sequelae of tumor treatment in the head and neck region are the main pathologic entities.Predominantly ENT physicians and phoniatrists, are asked for diagnostics and therapy who will coordinate the interdisciplinary treatment according to the endoscopic findings.A differentiated approach in history, diagnostics, and symptom oriented treatment is necessary for the mostly complex disorders. The integration of non-medical personnel such as logopeds (speech language pathologists), physiotherapists, and occupational therapists in planning and executing an effective therapy expands and completes the patient-oriented care. Conservative treatment by these therapists is an important pillar in the treatment. Parts of the specific diagnostics can be taken over by them in close cooperation.In particular an interdisciplinary cooperation with the staff from intensive care medicine is indispensable.The diagnostic procedures of specific endoscopy as described in this position paper are part of the primary and fundamental tasks of ENT specialists and phoniatrists.Endoscopy is a medical service that is basically not delegable. Consequently substitution of the physician is precluded.

Cortical innervation of the hypoglossal nucleus in the non-human primate (Macaca mulatta)

The corticobulbar projection to the hypoglossal nucleus was studied from the frontal, parietal, cingulate, and insular cortices in the rhesus monkey by using high-resolution anterograde tracers and stereology. The hypoglossal nucleus received bilateral input from the face/head region of the primary (M1), ventrolateral pre- (LPMCv), supplementary (M2), rostral cingulate (M3), and caudal cingulate (M4) motor cortices. Additional bilateral corticohypoglossal projections were found from the dorsolateral premotor cortex (LPMCd), ventrolateral proisocortical motor area (ProM), ventrolateral primary somatosensory cortex (S1), rostral insula, and pregenual region of the anterior cingulate gyrus (areas 24/32). Dense terminal projections arose from the ventral region of M1, and moderate projections from LPMCv and rostral part of M2, with considerably fewer hypoglossal projections arising from the other cortical regions. These findings demonstrate that extensive regions of the non-human primate cerebral cortex innervate the hypoglossal nucleus. The widespread and bilateral nature of this corticobulbar connection suggests recovery of tongue movement after cortical injury that compromises a subset of these areas, may occur from spared corticohypoglossal projection areas located on the lateral, as well as medial surfaces of both hemispheres. Since functional imaging studies have shown that homologous cortical areas are activated in humans during tongue movement tasks, these corticobulbar projections may exist in the human brain.

Sequential evolution of cortical activity and effective connectivity of swallowing using fMRI

Swallowing consists of a hierarchical sequence of primary motor and somatosensory processes. The temporal interplay of different phases is complex and clinical disturbances frequent. Of interest was the temporal interaction of the swallowing network. Time resolution optimized functional magnetic resonance imaging was used to describe the temporal sequence of representation sites of swallowing and their functional connectivity. Sixteen young healthy volunteers were investigated who swallowed 2 ml of water 20 times per run with a repetition time for functional imaging of 514 ms. After applying the general linear model approach to identify activation magnitude in preselected regions of interest repeated measures analysis of variance (rmANOVA) was used to detect relevant effects on lateralization, time, and onset. Furthermore, dynamic causal modeling (DCM) was applied to uncover where the input enters the model and the way in which the cortical regions are connected. The temporal analysis revealed a successive activation starting at the premotor cortex, supplementary motor area (SMA), and bilateral thalamus, followed by the primary sensorimotor cortex, the posterior insula, and cerebellum and culminating with activation in the pons shortly before subsiding. The rmANOVA revealed that activation was lateralized initially to the left hemisphere and gradually moved to the right hemisphere over time. The group random effects DCM analysis resulted in a most likely model that consisted of inputs to SMA and M1S1, bidirectionally connected, and a one-way connection from M1S1 to the posterior insula.

Diagnostic value of "dysphagia limit" for neurogenic dysphagia: 17 years of experience in 1278 adults

OBJECTIVE

Neurogenic dysphagia (ND) is a prevalent condition that accounts for significant mortality and morbidity worldwide. Screening and follow-up are critical for early diagnosis and management which can mitigate its complications and be cost-saving. The aims of this study are to provide a comprehensive investigation of the dysphagia limit (DL) in a large diverse cohort and to provide a longitudinal assessment of dysphagia in a subset of subjects.

METHODS

We developed a quantitative and noninvasive method for objective assessment of dysphagia by using laryngeal sensor and submental electromyography. DL is the volume at which second or more swallows become necessary to swallow the whole amount of bolus. This study represents 17 years experience with the DL approach in assessing ND in a cohort of 1278 adult subjects consisting of 292 healthy controls, 784 patients with dysphagia, and 202 patients without dysphagia. A total of 192 of all patients were also reevaluated longitudinally over a period of 1-19 months.

RESULTS

DL has 92% sensitivity, 91% specificity, 94% positive predictive value, and 88% negative predictive value with an accuracy of 0.92. Patients with ALS, stroke, and movement disorders have the highest sensitivity (85-97%) and positive predictive value (90-99%). The clinical severity of dysphagia has significant negative correlation with DL (r=-0.67, p<0.0001).

CONCLUSIONS

We propose the DL as a reliable, quick, noninvasive, quantitative test to detect and follow both clinical and subclinical dysphagia and it can be performed in an EMG laboratory.

SIGNIFICANCE

Our study provides specific quantitative features of DL test that can be readily utilized by the neurologic community and nominates DL as an objective and robust method to evaluate dysphagia in a wide range of neurologic conditions.

Differential psychophysiological interactions of insular subdivisions during varied oropharyngeal swallowing tasks

Abstract The insula is a highly integrated cortical region both anatomically and functionally. It has been shown to have cognitive, social-emotional, gustatory, and sensorimotor functions. Insular involvement in both normal and abnormal swallowing behavior is well established, yet its functional connectivity is unclear. Studies of context-dependent connectivity, or the connectivity during different task conditions, have the potential to reveal information about synaptic function of the insula. The goal of this study was to examine the functional connectivity of specific insular regions (ventral anterior, dorsal anterior, and posterior) with distant cortical regions during four swallowing conditions (water, sour, e-stim, and visual biofeedback) using generalized psychophysiological interactions (gPPI). In 19 healthy adults, we found that the visual biofeedback condition was associated with the most and strongest increases in functional connectivity. The posterior insula/rolandic operculum regions had the largest clusters of increases in functional connectivity, but the ventral anterior insula was functionally connected to a more diverse array of cortical regions. Also, laterality assessments showed left lateralized increases in swallowing functional connectivity. Our results are aligned with reports about the insula's interconnectivity and extensive involvement in multisensory and cognitive tasks.

Changes in hemodynamic signals accompanying motor imagery and motor execution of swallowing: a near-infrared spectroscopy study

In the present study we investigated hemodynamic changes in the brain in response to motor execution (ME) and motor imagery (MI) of swallowing using near-infrared spectroscopy (NIRS). Previous studies provide evidence that ME and MI of limb movements lead to comparable brain activation patterns indicating the potential value of MI for motor rehabilitation. In this context, identifying brain correlates of MI of swallowing may be potentially useful for the treatment of dysphagia. Fourteen healthy participants actively swallowed water (ME) and mentally imagined to swallow water (MI) in a randomized order while changes in concentration of oxygenated hemoglobin (oxy-Hb) and deoxygenated hemoglobin (deoxy-Hb) were assessed. MI and ME led to the strongest NIRS signal changes in the inferior frontal gyrus. During and after ME, oxy-Hb significantly increased, with a maximum peak around 15s after task onset. In contrast, oxy-Hb decreased during MI compared to a rest period probably because of motor inhibition mechanisms. Changes in deoxy-Hb were largely comparable between MI and ME, especially when participants used a kinesthetic motor imagery strategy during MI compared to no specific strategy. Hence, the present study provides new evidence concerning timing and topographical distribution of the hemodynamic response during ME and MI of swallowing.