Functional magnetic resonance imaging study on dysphagia after unilateral hemispheric stroke: a preliminary study

Functional brain networks associated with the urge for action: Implications for pathological urge

Tics in Tourette syndrome (TS) are often preceded by sensory urges that drive the motor and vocal symptoms. Many everyday physiological behaviors are associated with sensory phenomena experienced as an urge for action, which may provide insight into the neural correlates of this pathological urge to tic that remains elusive. This study aimed to identify a brain network common to distinct physiological behaviors in healthy individuals, and in turn, examine whether this network converges with a network we previously localized in TS, using novel 'coordinate network mapping' methods. Systematic searches were conducted to identify functional neuroimaging studies reporting correlates of the urge to micturate, swallow, blink, or cough. Using activation likelihood estimation meta-analysis, we identified an 'urge network' common to these physiological behaviors, involving the bilateral insula/claustrum/inferior frontal gyrus/supplementary motor area, mid-/anterior- cingulate cortex (ACC), right postcentral gyrus, and left thalamus/precentral gyrus. Similarity between the urge and TS networks was identified in the bilateral insula, ACC, and left thalamus/claustrum. The potential role of the insula/ACC as nodes in the network for bodily representations of the urge to tic are discussed.

Cortical compensation mechanism for swallowing recovery in patients with medullary infarction-induced dysphagia

Introduction

This study aims to examine brain activity during different swallowing actions in patients with dysphagia caused by medullary infarction (MI) before and after treatment using blood oxygen level-dependent (BOLD) functional magnetic resonance imaging.

Methods

Fifteen patients were enrolled in this study. Brain activation during saliva swallowing and effortful saliva swallowing was observed using BOLD imaging in the acute phase of stroke and after 4 weeks of rehabilitation training. Differences in the activation of brain regions during saliva swallowing before and after treatment, during effortful saliva swallowing before and after treatment, and between the two swallowing actions before and after treatment were compared.

Results

In the acute phase of stroke, only the bilateral precentral and left lingual gyrus were partially activated during saliva swallowing, and there was no obvious activation in the insula. Effortful saliva swallowing activated more brain regions than saliva swallowing before treatment, including the bilateral supplementary motor area (SMA), postcentral gyrus, and right insular cortex. The number of brain regions activated during saliva swallowing increased after treatment, including the bilateral precentral gyrus, postcentral gyrus, insula, thalamus, and SMA.

Discussion

Cortical activation increases after recovery from dysphagia, and the increased activation of the postcentral gyrus might play a functional compensatory role. Effortful saliva swallowing is a more effective rehabilitation training method for patients with dysphagia caused by MI.

Correlation between lesion location and dysphagia characteristics in post-stroke patients

OBJECTIVE

To assess the correlation between lesion location and swallowing function characteristics in post-stroke dysphagia (PSD) patients.

MATERIALS AND METHODS

We enrolled 133 PSD. The patients were divided into supratentorial and infratentorial stroke groups. We compared the measurements in the videofluoroscopic swallowing study (VFSS) with 3ml and 5 ml of diluted and thickened barium liquid data between supratentorial and brainstem stroke groups. We further compared the difference of VFSS measurements between patients with left hemispheric or right hemispheric lesions (further divided into unilateral hemispheric cortical and subcortical subgroups) and brianstem leison stroke group.To explore the lesion location's effect on different bolus volume, the VFSS measurements of 3ml and 5ml in each subgroups were compared respectively. The measurements of VFSS included the oral transit time, soft palate elevation duration, hyoid bone movement duration (HMD), UES opening duration, pharyngeal transit duration (PTD), stage of ansition duration, and laryngeal closure duration (LCD), the upper esophageal sphincter opening (UESO), hyoid bone superior horizontal displacement, and hyoid bone anterior horizontal displacement. General swallowing function was assessed using the Penetration Aspiration Scale (PAS) and Functional Oral Intake Scale (FOIS). We performed the paired t-test, Spearman's correlation, and Kruskal-Wallis test analysis to characterize the parameters among the groups.

RESULTS

Fifty-eight patients were assessed in the final analysis. The HMD (p = 0.019), PTD (p = 0.048) and LCD (p = 0.013) were significantly different between the supratentorial and brainstem lesion groups in 5ml volume. The HMD was significantly different (p = 0.045) between the left cortical and brainstem lesion groups. Significant differences in the HMD (p = 0.037) and LCD (p = 0.032) between the left subcortical and brainstem lesion groups were found in 5ml volume bolus. There was no group different when taking the 3ml volume bolus. Regarding the relationship between food bolus volume and swallowing functions, only the UESO demonstrated a significant difference in the subcortical lesion of the right hemisphere (p = 0.0032) compared the 3 ml and 5 ml volume bolus. The PTD demonstrated a moderate correlation with the PAS scores (r = 0.38, p = 0.0044). The HMD (r = 0.32, p = 0.018) and LCD (r = 0.29, p = 0.039) demonstrated weak correlations with the PAS scores. We did not identify any correlation between the VFSS parameters and FOIS scores in each subgroup level.

CONCLUSION

The PSD with brainstem lesion shows more sever dysfunction in the pharyngeal phases. The left hemisphere was engaged in both the oral and pharyngeal phases. Lesions in the bilateral cortical, subcortical, and brainstem regions may impair sensory input.

The neurorehabilitation of post-stroke dysphagia: Physiology and pathophysiology

Swallowing is a complex process involving the precise contractions of numerous muscles of the head and neck, which act to process and shepherd ingested material from the oral cavity to its eventual destination, the stomach. Over the past five decades, information from animal and human studies has laid bare the complex network of neurones in the brainstem, cortex and cerebellum that are responsible for orchestrating each normal swallow. Amidst this complexity, problems can and often do occur that result in dysphagia, defined as impaired or disordered swallowing. Dysphagia is common, arising from multiple varied disease processes that can affect any of the neuromuscular structures involved in swallowing. Post-stroke dysphagia (PSD) remains the most prevalent and most commonly studied form of dysphagia and, as such, provides an important disease model to assess dysphagia physiology and pathophysiology. In this review, we explore the complex neuroanatomical processes that occur during normal swallowing and PSD. This includes how strokes cause dysphagia, the mechanisms through which natural neuroplastic recovery occurs, current treatments for patients with persistent dysphagia and emerging neuromodulatory treatments.

Swallow-related Brain Activity in Post-total Laryngectomy Patients: A Case Series Study

Background

Total laryngectomy is a surgical procedure to completely remove the hyoid bone, larynx, and associated muscles as a curative treatment for laryngeal cancer. This leads to insufficient swallowing function with compensative movements of the residual tongue to propel the food bolus to the pharynx and esophagus. However, the neurophysiological mechanisms of compensative swallowing after total laryngectomy remain unclear. Recently, swallowing-related cortical activation such as event-related desynchronization (ERD) during swallowing has been reported in healthy participants and neurological patients with dysphagia. Abnormal ERD elucidates the pathophysiological cortical activities that are related to swallowing. No report has investigated ERD in post-total laryngectomy patients.

Case

We investigated ERD during volitional swallowing using electroencephalography in three male patients after total laryngectomy for laryngeal cancer (age and time after surgery: Case 1, 75 years, 10 years; Case 2, 85 years, 19 years; Case 3, 73 years, 19 years). In video fluorographic swallowing studies, we observed compensatory tongue movements such as posterior-inferior retraction of the tongue and contact on the posterior pharyngeal wall in all three cases. Significant ERD was localized in the bilateral medial sensorimotor areas and the left lateral parietal area in Case 1, in the bilateral frontal and left temporal areas in Case 2, and in the left prefrontal and premotor areas in Case 3.

Discussion

These results suggest that cortical activities related to swallowing might reflect cortical reorganization for modified swallowing movements of residual tongue muscles to compensate for reduced swallowing pressure in patients after total laryngectomy.

Hemodynamic signal changes and functional connectivity in acute stroke patients with dysphagia during volitional swallowing: a pilot study

BACKGROUND

Dysphagia is one of the major post-stroke complications, understanding post-stroke changes in cortical excitability and promoting early remodeling of swallowing-related cortical areas to enable accurate treatment is essential for recovery of patients.

OBJECTIVES

We aimed to investigate hemodynamic signal changes and functional connectivity in acute stroke patients with dysphagia compared to age-matched healthy participants in response to volitional swallowing using functional near-infrared spectroscopy (fNIRS) in this pilot study.

METHODS

Patients with first-ever post-stroke dysphagia having an onset of 1-4 weeks and age-matched right-handed healthy subjects were recruited in our study. fNIRS with 47 channels was utilized to detect the oxyhemoglobin (HbO2 ) and reduced hemoglobin (HbR) concentration changes when volitional swallowing. Cohort analysis was performed by a one-sample t-test. Two-sample t-test was utilized to compare the difference in cortical activation between patients with post-stroke dysphagia and healthy subjects. Furthermore, the relative changes in the concentration of the HbO2 throughout the experimental procedure were extracted for the functional connectivity analysis. The Pearson correlation coefficients of the HbO2 concentration of each channel were analyzed on a time series, and then a Fisher Z transformation was then performed, and the transformed values were defined as the functional connection strengths between the channels.

RESULTS

In this present study, a total of nine patients with acute post-stroke dysphagia were enrolled in the patient group and nine age-matched healthy participants in the healthy control group. Our study observed that the extensive regions of the cerebral cortex were activated in the healthy control group, while the activation area of patient group's cortical regions was quite limited. The mean functional connectivity strength of participants was 0.485 ± 0.105 in the healthy control group, and 0.252 ± 0.146 in the patient group, with a significant difference between the two groups (p = 0.001).

CONCLUSION

Compared to the healthy individuals, cerebral cortex regions of acute stroke patients were only marginally activated during volitional swallowing task, and the average functional connectivity strength of cortical network in patients was relatively weaker.

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.

Neural basis of dysphagia in stroke: A systematic review and meta-analysis

Objectives

Dysphagia is a major cause of stroke infection and death, and identification of structural and functional brain area changes associated with post-stroke dysphagia (PSD) can help in early screening and clinical intervention. Studies on PSD have reported numerous structural lesions and functional abnormalities in brain regions, and a systematic review is lacking. We aimed to integrate several neuroimaging studies to summarize the empirical evidence of neurological changes leading to PSD.

Methods

We conducted a systematic review of studies that used structural neuroimaging and functional neuroimaging approaches to explore structural and functional brain regions associated with swallowing after stroke, with additional evidence using a live activation likelihood estimation (ALE) approach.

Results

A total of 35 studies were included, including 20 studies with structural neuroimaging analysis, 14 studies with functional neuroimaging analysis and one study reporting results for both. The overall results suggest that structural lesions and functional abnormalities in the sensorimotor cortex, insula, cerebellum, cingulate gyrus, thalamus, basal ganglia, and associated white matter connections in individuals with stroke may contribute to dysphagia, and the ALE analysis provides additional evidence for structural lesions in the right lentiform nucleus and right thalamus and functional abnormalities in the left thalamus.

Conclusion

Our findings suggest that PSD is associated with neurological changes in brain regions such as sensorimotor cortex, insula, cerebellum, cingulate gyrus, thalamus, basal ganglia, and associated white matter connections. Adequate understanding of the mechanisms of neural changes in the post-stroke swallowing network may assist in clinical diagnosis and provide ideas for the development of new interventions in clinical practice.

Cerebral control of swallowing: An update on neurobehavioral evidence

This review aims to update the current knowledge on the cerebral control of swallowing. We review data from both animal and human studies spanning across the fields of neuroanatomy, neurophysiology and neuroimaging to evaluate advancements in our understanding in the brain's role in swallowing. Studies have collectively shown that swallowing is mediated by multiple distinct cortical and subcortical regions and that lesions to these regions can result in dysphagia. These regions are functionally connected in separate groups within and between the two hemispheres. While hemispheric dominance for swallowing has been reported in most human studies, the laterality is inconsistent across individuals. Moreover, there is a shift in activation location and laterality between swallowing preparation and execution, although such activation changes are less well-defined than that for limb motor control. Finally, we discussed recent neurostimulation treatments that may be beneficial for dysphagia after brain injury through promoting the reorganization of the swallowing neural network.

Research progress of clinical intervention and nursing for patients with post-stroke dysphagia

Post-stroke dysphagia (PSD) is a common and costly complication of stroke and is associated with increased mortality, morbidity, and hospitalization. Although most patients can spontaneously resume swallowing, there are still many patients who do not recover and even die. Despite multiple advances in the acute treatment and secondary prevention of stroke, the effective treatment of PSD remains a neglected area. Studies have shown that repair mechanisms of neurostimulation techniques and increased cortical activity play an important role in the treatment of PSD. In addition, nutritional interventions are also crucial for the treatment of malnutrition in PSD patients. Therefore, this article reviews the effects of the current main clinical treatment methods and nutritional interventions on the treatment and rehabilitation of PSD patients. It also emphasized the necessity of developing an individualized care plan for PSD patients, which is of great significance to promote the clinical treatment, nutritional status, prognosis, and quality of life of PSD patients.

Hemodynamic signal changes and swallowing improvement of repetitive transcranial magnetic stimulation on stroke patients with dysphagia: A randomized controlled study

Objective

Our study aims to measure the cortical correlates of swallowing execution in patients with dysphagia after repetitive transcranial magnetic stimulation (rTMS) therapy using functional near-infrared spectroscopy (fNIRS), and observe the change of pattern of brain activation in stroke patients with dysphagia after rTMS intervention. In addition, we tried to analyze the effect of rTMS on brain activation in dysphagia patients with different lesion sides. This study also concentrated on the effect of stimulating the affected mylohyoid cortical region by 5 Hz rTMS, providing clinical evidence for rTMS therapy of dysphagia in stroke patients.

Methods

This study was a sham-controlled, single-blind, randomized controlled study with a blinded observer. A total of 49 patients completed the study, which was randomized to the rTMS group (n = 23) and sham rTMS group (n = 26) by the random number table method. The rTMS group received 5 Hz rTMS stimulation to the affected mylohyoid cortical region of the brain and the sham rTMS group underwent rTMS using the same parameters as the rTMS group, except for the position of the coil. Each patient received 2 weeks of stimulation followed by conventional swallowing therapy. Standardized Swallowing Assessment (SSA), Fiberoptic Endoscopic Dysphagia Severity Scale (FEDSS), Penetration-Aspiration Scale (PAS), and functional oral intake status were assessed at two times: baseline (before treatment) and 2 weeks (after intervention). Meanwhile, we use the fNIRS system to measure the cerebral hemodynamic changes during the experimental procedure.

Results

The rTMS group exhibited significant improvement in the SSA scale, FEDSS scale, and PAS scale after rTMS therapy (all P < 0.001). The sham rTMS group had the same analysis on the same scales (all P < 0.001). There was no significant difference observed in clinical assessments at 2 weeks after baseline between the rTMS group and sham rTMS group (all P > 0.05). However, there were statistically significant differences between the two groups in the rate of change in the FEDSS score (P = 0.018) and PAS score (P = 0.004), except for the SSA score (P = 0.067). As for the removal rate of the feeding tube, there was no significant difference between the rTMS group and sham rTMS group (P = 0.355), but there was a significant difference compared with the baseline characteristics in both groups (PrTMS < 0.001, PshamrTMS = 0.002). In fNIRS analysis, the block average result showed differences in brain areas RPFC (right prefrontal cortex) and RMC (right motor cortex) significantly between the rTMS group and sham rTMS group after intervention (Pchannel30 = 0.046, Pchannel16 = 0.006). In the subgroup analysis, rTMS group was divided into left-rTMS group and right-rTMS group and sham rTMS group was divided into sham left-rTMS group and sham right-rTMS group. The fNIRS results showed no significance in block average and block differential after intervention between the left-rTMS group and sham left-rTMS group, but differences were statistically significant between the right-rTMS group and sham right-rTMS group in block average: channel 30 (T = −2.34, P = 0.028) in LPFC (left prefrontal cortex) and 16 (T = 2.54, P = 0.018) in RMC. After intervention, there was no significance in left-rTMS group compared with baseline, but in right-rTMS group, channel 27 (T = 2.18, P = 0.039) in LPFC and 47 (T = 2.17, P = 0.039) in RPFC had significance in block differential. In the sham rTMS group, neither sham left-rTMS group and sham right-rTMS group had significant differences in block average and block differential in each brain area after intervention (P > 0.05).

Conclusions

The present study confirmed that a 5-Hz rTMS is feasible at the affected mylohyoid cortical region in post-stroke patients with dysphagia and rTMS therapy can alter cortical excitability. Based on previous studies, there is a dominant hemisphere in swallowing and the results of our fNIRS analysis seemed to show a better increase in cortical activation on the right side than on the left after rTMS of the affected mylohyoid cortical region. However, there was no difference between the left and right hemispheres in the subgroup analysis. Nevertheless, the present study provides a novel and feasible method of applying fNIRS to assessment in stroke patients with dysphagia.

Increased cortical-medulla functional connectivity is correlated with swallowing in dysphagia patients with subacute infratentorial stroke

Patients with infratentorial stroke (IS) exhibit more severe dysphagia and a higher risk of aspiration than patients with supratentorial stroke. Nevertheless, a large proportion of patients with IS regain swallowing function within 6 months; however, the neural mechanism for this recovery remains unclear. We aimed to investigate possible neuroplastic changes involved using functional magnetic resonance imaging (fMRI) and their relation to swallowing function. We assessed 21 patients with IS (mean age: 59.9 ± 11.1 years) exhibiting dysphagia in the subacute phase and 21 healthy controls (mean age: 57.1 ± 7.8 years). Patient evaluations were based on the functional oral intake scale (FOIS), videofluoroscopic swallow study (VFSS), and fMRI. Temporal swallowing measures and the penetration-aspiration scale (PAS) were obtained using VFSS. Whole-brain-medulla resting-state functional connectivity (rsFC) was calculated and compared between patients and healthy controls. The rsFCs were also correlated with functional measures within the patient group. In patients with IS, whole-brain-medulla rsFCs were significantly higher in the precuneus, the left and right precentral gyrus, and the right supplementary motor area compared to those in healthy controls (P < 0.001, family-wise error-corrected cluster-level P < 0.05). The rsFCs to the medulla for the left (r = -0.507, P = 0.027) and right side (r = -0.503, P = 0.028) precentral gyrus were negatively correlated with the PAS. The rsFC between the left (r = 0.470, P = 0.042) and right (r = 0.459, P = 0.048) precentral gyrus to the medulla was positively correlated with upper esophageal sphincter opening durations (UOD). In addition, PAS was also correlated with UOD (r = -0.638, P = 0.003) whereas the laryngeal closure duration was correlated with the hyoid bone movement duration (r = 0.550, P = 0.015). Patients with IS exhibited overall modulation of cortical-medulla connectivity during the subacute phase. Patients with higher connectivities showed better swallowing performance. These findings support that there is cortical involvement in swallowing regulation after IS and can aid in determining potential treatment targets for dysphagia.

Risk factors of dysphagia in patients with ischemic stroke: A meta-analysis and systematic review

Background

Dysphagia is a common yet serious complication in stroke patients. We aimed to conduct a meta-analysis and systematic review to evaluate the risk factors of dysphagia in patients with ischemic stroke, to provide insights to the clinical treatment and nursing care of dysphagia.

Methods

We searched PubMed, Embase, Cochrane Library, Web of Science, China National Knowledge Infrastructure (CNKI) and Wanfang Database, China Biomedical Literature Database (CBM) for studies on dysphagia in patients with ischemic stroke up to January 31, 2022. The quality of the literature was evaluated using the Newcastle-Ottawa scale. Meta-analysis was performed using RevMan 5.3 software.

Results

A total of 10 studies involving 4637 ischemic stroke patients were included, 1183(25.51%) patients had dysphagia after stroke. The synthesized outcomes showed that elder age (SMD = 0.42, 95%CI:0.34–0.50), hypertension (OR = 1.96, 95%CI:1.48–2.61), diabetes (OR = 1.83, 95%CI:1.47–2.28), brainstem stroke (OR = 2.12, 95%CI:1.45–3.09) were associated with dysphagia in patients with ischemic stroke (all P<0.05). There was no significant difference in the gender between dysphagia and no dysphagia patients (OR = 1.07, 95%CI:0.91–1.27, P = 0.40). Egger regression tests indicated there were no significant publication biases in the synthesized outcomes (all P>0.05).

Conclusions

Elder age, hypertension, diabetes and brainstem stroke are associated with the development of dysphagia in patients with ischemic stroke. Attention should be paid to the assessment and early intervention of those risk factors for dysphagia to improve the prognosis of stroke patients.

Case Report: Event-Related Desynchronization Observed During Volitional Swallow by Electroencephalography Recordings in ALS Patients With Dysphagia

Dysphagia is a severe disability affecting daily life in patients with amyotrophic lateral sclerosis (ALS). It is caused by degeneration of both the bulbar motor neurons and cortical motoneurons projecting to the oropharyngeal areas. A previous report showed decreased event-related desynchronization (ERD) in the medial sensorimotor areas in ALS dysphagic patients. In the process of degeneration, brain reorganization may also be induced in other areas than the sensorimotor cortices. Furthermore, ALS patients with dysphagia often show a longer duration of swallowing. However, there have been no reports on brain activity in other cortical areas and the time course of brain activity during prolonged swallowing in these patients. In this case report, we investigated the distribution and the time course of ERD and corticomuscular coherence (CMC) in the beta (15–25 Hz) frequency band during volitional swallow using electroencephalography (EEG) in two patients with ALS. Case 1 (a 71-year-old man) was diagnosed 2 years before the evaluation. His first symptom was muscle weakness in the right hand; 5 months later, dysphagia developed and exacerbated. Since his dietary intake decreased, he was given an implantable venous access port. Case 2 (a 64-year-old woman) was diagnosed 1 year before the evaluation. Her first symptom was open-nasal voice and dysarthria; 3 months later, dysphagia developed and exacerbated. She was given a percutaneous endoscopic gastrostomy. EEG recordings were performed during volitional swallowing, and the ERD was calculated. The average swallow durations were 7.6 ± 3.0 s in Case 1 and 8.3 ± 2.9 s in Case 2. The significant ERD was localized in the prefrontal and premotor areas and lasted from a few seconds after the initiation of swallowing to the end in Case 1. The ERD was localized in the lateral sensorimotor areas only at the initiation of swallowing in Case 2. CMC was not observed in either case. These results suggest that compensatory processes for cortical motor outputs might depend on individual patients and that a new therapeutic approach using ERD should be developed according to the individuality of ALS patients with dysphagia.

Neural correlates in the development of and recovery from dysphagia after supratentorial stroke: A prospective tractography study

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Stroke may lead to unilateral or bilateral CBT changes regardless of dysphagia.

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Poor fractional anisotropy of the unaffected sides relates to limited recovery.

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Swallowing recovery may depend on the integrity of the unaffected CBT.

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Bi-hemispheric reorganization of the CBT is associated with swallowing recovery.

Background

Methods

Results

Conclusions

Systematic Review and Network Meta-Analysis of Noninvasive Brain Stimulation on Dysphagia after Stroke

Background

Dysphagia is a common sequelae after stroke. Noninvasive brain stimulation (NIBS) is a tool that has been used in the rehabilitation process to modify cortical excitability and improve dysphagia.

Objective

To systematically evaluate the effect of NIBS on dysphagia after stroke and compare the effects of two different NIBS.

Methods

Randomized controlled trials about the effect of NIBS on dysphagia after stroke were retrieved from databases of PubMed, Embase, Cochrane Library, Web of Science, CNKI, Wanfang Data, VIP, and CBM, from inception to June 2021. The quality of the trials was assessed, and the data were extracted according to the Cochrane Handbook for Systematic Reviews of Interventions. A statistical analysis was carried out using RevMan 5.3 and ADDIS 1.16.8. The effect size was evaluated by using the standardized mean difference (SMD) and a 95% confidence interval (CI).

Results

Ultimately, 18 studies involving 738 patients were included. Meta-analysis showed that NIBS could improve the dysphagia outcome and severity scale (DOSS) score (standard mean difference (SMD) = 1.44, 95% CI 0.80 to 2.08, P < 0.05) and the water swallow test score (SMD = 6.23, 95% CI 5.44 to 7.03, P < 0.05). NIBS could reduce the standardized swallowing assessment (SSA) score (SMD = −1.04, 95% CI -1.50 to -0.58, P < 0.05), the penetration-aspiration scale (PAS) score (SMD = −0.85, 95% CI -1.33 to -0.36, P < 0.05), and the functional dysphagia scale score (SMD = −1.05, 95% CI -1.48 to -0.62, P < 0.05). Network meta-analysis showed that the best probabilistic ranking of the effects of two different NIBS on the DOSS score is rTMS (P = 0.52) > tDCS (P = 0.48), the best probabilistic ranking of the SSA score is rTMS (P = 0.72) > tDCS (P = 0.28), and the best probabilistic ranking of the PAS score is rTMS (P = 0.68) > tDCS (P = 0.32).

Conclusion

Existing evidence showed that NIBS could improve swallowing dysfunction and reduce the occurrence of aspiration after stroke, and that rTMS is better than tDCS. Limited by the number of included studies, more large-sample, multicenter, double-blind, high-quality clinical randomized controlled trials are still needed in the future to further confirm the results of this research.

Targeting the sensory feedback within the swallowing network-Reversing artificially induced pharyngolaryngeal hypesthesia by central and peripheral stimulation strategies

Pharyngolaryngeal hypesthesia is a major reason for dysphagia in various neurological diseases. Emerging neuromodulation devices have shown potential to foster dysphagia rehabilitation, but the optimal treatment strategy is unknown. Because functional imaging studies are difficult to conduct in severely ill patients, we induced a virtual sensory lesion in healthy volunteers and evaluated the effects of central and peripheral neurostimulation techniques. In a sham-controlled intervention study with crossover design on 10 participants, we tested the potential of (peripheral) pharyngeal electrical stimulation (PES) and (central) transcranial direct current stimulation (tDCS) to revert the effects of lidocaine-induced pharyngolaryngeal hypesthesia on central sensorimotor processing. Changes were observed during pharyngeal air-pulse stimulation and voluntary swallowing applying magnetoencephalography before and after the interventions. PES induced a significant (p < .05) increase of activation during swallowing in the bihemispheric sensorimotor network in alpha and low gamma frequency ranges, peaking in the right premotor and left primary sensory area, respectively. With pneumatic stimulation, significant activation increase was found after PES in high gamma peaking in the left premotor area. Significant changes of brain activation after tDCS could neither be detected for pneumatic stimulation nor for swallowing. Due to the peripheral cause of dysphagia in this model, PES was able to revert the detrimental effects of reduced sensory input on central processing, whereas tDCS was not. Results may have implications for therapeutic decisions in the clinical context.

Electroacupuncture Involved in Motor Cortex and Hypoglossal Neural Control to Improve Voluntary Swallowing of Poststroke Dysphagia Mice

The descending motor nerve conduction of voluntary swallowing is mainly launched by primary motor cortex (M1). M1 can activate and regulate peripheral nerves (hypoglossal) to control the swallowing. Acupuncture at “Lianquan” acupoint (CV23) has a positive effect against poststroke dysphagia (PSD). In previous work, we have demonstrated that electroacupuncture (EA) could regulate swallowing-related motor neurons and promote swallowing activity in the essential part of central pattern generator (CPG), containing nucleus ambiguus (NA), nucleus of the solitary tract (NTS), and ventrolateral medulla (VLM) under the physiological condition. In the present work, we have investigated the effects of EA on the PSD mice in vivo and sought evidence for PSD improvement by electrophysiology recording and laser speckle contrast imaging (LSCI). Four main conclusions can be drawn from our study: (i) EA may enhance the local field potential in noninfarction area of M1, activate the swallowing-related neurons (pyramidal cells), and increase the motor conduction of noninfarction area in voluntary swallowing; (ii) EA may improve the blood flow in both M1 on the healthy side and deglutition muscles and relieve PSD symptoms; (iii) EA could increase the motor conduction velocity (MCV) in hypoglossal nerve, enhance the EMG of mylohyoid muscle, alleviate the paralysis of swallowing muscles, release the substance P, and restore the ability to drink water; and (iv) EA can boost the functional compensation of M1 in the noninfarction side, strengthen the excitatory of hypoglossal nerve, and be involved in the voluntary swallowing neural control to improve PSD. This research provides a timely and necessary experimental evidence of the motor neural regulation in dysphagia after stroke by acupuncture in clinic.

Cortical and Subcortical Control of Swallowing-Can We Use Information From Lesion Locations to Improve Diagnosis and Treatment for Patients With Stroke?

Purpose Swallowing is a complex process, mediated by a broad bilateral neural network that spans from the brainstem to subcortical and cortical brain structures. Although the cortex's role in swallowing was historically neglected, we now understand, especially through clinical observations and research of patients with stroke, that it substantially contributes to swallowing control. Neuroimaging techniques (e.g., magnetic resonance imaging) have helped significantly to elucidate the role of cortical and subcortical brain areas, in general, and the importance of specific areas in swallowing control in healthy individuals and patients with stroke. We will review recent discoveries in cortical and subcortical neuroimaging research studies and their generalizability across patients to discuss their potential implications and translation to dysphagia diagnosis and treatment in clinical practice. Conclusions Stroke lesion locations have been identified that are commonly associated across patients with the occurrence and recovery of dysphagia, suggesting that clinical brain scans provide useful information for improving the diagnosis and treatment of patients with stroke. However, individual differences in brain structure and function limit the generalizability of these relationships and emphasize that the extent of the motor and sensory pathology in swallowing, and how the patient recovers, also depends on a patient's individual brain constitution. The involvement of the damaged brain tissue in swallowing control before the stroke and the health of the residual, undamaged brain tissue are crucial factors that can differ between individuals.

Role of bilateral corticobulbar tracts in dysphagia after middle cerebral artery stroke

BACKGROUND AND PURPOSE

The corticobulbar tract is a potential neural pathway involved in swallowing. The frontal operculum, insular cortex, corona radiata and internal capsule, which are frequently involved in middle cerebral artery (MCA) strokes, are locations in which lesions cause dysphagia. However, it is unclear whether the locations are linked to the corticobulbar tract or whether corticobulbar tract integrity is associated with dysphagia severity. This study aimed to assess the association between corticobulbar tract integrity and dysphagia severity after MCA stroke.

METHODS

Thirty dysphagic patients after MCA stroke and 27 healthy controls were examined. Diffusion tensor imaging (DTI)-derived parameters of the corticobulbar tract were compared between patient and control groups. Next, patients were divided into mild and moderate-to-severe dysphagia groups, and DTI-derived parameters of the corticobulbar tract were compared between the subgroups. Logistic regression analysis was used to determine the association between corticobulbar tract integrity and dysphagia severity.

RESULTS

The tract volume (TV) of the affected corticobulbar tract was lower in dysphagic patients than in healthy controls (P < 0.001). According to dysphagia severity, TV of the unaffected corticobulbar tract was higher in the mild dysphagia group than in the moderate-to-severe dysphagia group (P = 0.012). TV of the unaffected corticobulbar tract was independently associated with dysphagia severity according to the logistic regression model (adjusted odds ratio 0.817, 95% confidence interval 0.683-0.976).

CONCLUSIONS

The corticobulbar tract was affected after MCA stroke and may be associated with dysphagia. A higher corticobulbar TV in the unaffected hemisphere was indicative of better swallowing function in dysphagic patients after MCA stroke.

What Happens to Swallowing Muscles after Stroke?: A Prospective Randomized Controlled Electrophysiological Study

Background

Stroke is the most frequent reason of neurological dysphagia Electrophysiological studies can be used to evaluate oral, pharyngeal and initial phase of esophageal phase.

Aims

This study aims to noninvasively evaluate mastication, mimic, and tongue muscles of stroke patients, which play an important role in the oral phase of swallowing process and compare them with healthy individuals.

Setting and Design

This study was conducted at the Physical Medicine and Rehabilitation Clinic of our hospital between January 2014 and December 2016.

Materials and Methods

Fifty-one patients who were admitted to our clinic with stroke and 51 healthy individuals were evaluated for the study. Demographic features of individuals were recorded. The swallowing intervals and motor action potentials (MAPs) of trigeminal, facial and hypoglossal nerves were measured. After four weeks of treatment schedule, patients were re-evaluated.

Statistical Analysis

The Wilcoxon Signed Rank test, the Mann-Whitney U test and Fisher exact test were used in this study.

Results

The all swallowing intervals were found prolonged compared to the healthy controls (P < 0.05). The MAPs of the masseter, orbicularis oculi, and intrinsic tongue muscles were significantly lower in patient group (P < 0.05). After treatment, we found significant improvement for all parameters in patient group, but the swallowing intervals were still significantly prolonged, and MAPs of these muscles were still lower (P < 0.05).

Conclusion

Although swallowing is examined as different phases, the process is complicated and should be evaluated totally. In post-stroke dysphagia, oral phase of swallowing process is as important as phayngeal phase and perioral, mastication, and tongue muscles are influenced even in an early period as a month.

Predictors and associating factors of nasogastric tube removal: Clinical and brain imaging data analysis in post-stroke dysphagia

BACKGROUND/PURPOSE

Post-stroke dysphagia is a frequent complication. Although most patients with dysphagia recover after the acute phase, some patients require long-term enteral feeding, either through a nasogastric (NG) or gastrostomy tube; the effectiveness of using either tube is still under debate. This study elucidated the natural course of NG tube installation and removal and examined the predictors and associating factors based on clinical and brain imaging data.

METHODS

This retrospective cohort study with medical record reviews recruited patients received NG tube installation after their acute stroke events between January 1, 2016, and December 31, 2016. Inclusion criteria were subjects above 20 years of age and with a diagnosis of a newly onset stroke except SAH whose comprehensive clinical and imaging data were available. Survival analysis was performed for the right-censored data because some patients were lost to follow-up after discharge or transferal.

RESULTS

In total we recruited 135 patients. Among these patients, the timing of their NG tube removal reached a plateau at 12-16 weeks after stroke. The modified Rankin score on discharge, representing the overall subacute disease status, was the most significant factor. Other clinical variables could be divided into 2 categories: baseline patient characteristics and stroke event severity. Moreover, semi-quantitative brain imaging scores corresponding to the aforementioned 3 categories were correlated significantly.

CONCLUSION

In Taiwan, the NG tube removal rate reached a plateau at around 12-16 weeks after stroke onset. Variables related to long-term NG tube use were divided into baseline characteristics of patient and stroke event severity.

Functional Adaptation of Oromotor Functions and Aging: A Focused Review of the Evidence From Brain Neuroimaging Research

“Practice makes perfect” is a principle widely applied when one is acquiring a new sensorimotor skill to cope with challenges from a new environment. In terms of oral healthcare, the traditional view holds that restoring decayed structures is one of the primary aims of treatment. This assumes that the patient’s oromotor functions would be recovered back to normal levels after the restoration. However, in older patients, such a structural–functional coupling after dental treatment shows a great degree of individual variations. For example, after prosthodontic treatment, some patients would adapt themselves quickly to the new dentures, while others would not. In this Focused Review, I argue that the functional aspects of adaptation—which would be predominantly associated with the brain mechanisms of cognitive processing and motor learning—play a critical role in the individual differences in the adaptive behaviors of oromotor functions. This thesis is critical to geriatric oral healthcare since the variation in the capacity of cognitive processing and motor learning is critically associated with aging. In this review, (a) the association between aging and the brain-stomatognathic axis will be introduced; (b) the brain mechanisms underlying the association between aging, compensatory behavior, and motor learning will be briefly summarized; (c) the neuroimaging evidence that suggests the role of cognitive processing and motor learning in oromotor functions will be summarized, and critically, the brain mechanisms underlying mastication and swallowing in older people will be discussed; and (d) based on the current knowledge, an experimental framework for investigating the association between aging and the functional adaptation of oromotor functions will be proposed. Finally, I will comment on the practical implications of this framework and postulate questions open for future research.

Reduced tongue force and functional swallowing changes in a rat model of post stroke dysphagia

PURPOSE

Dysphagia is a common problem after stroke that is often associated with tongue weakness. However, the physiological mechanisms of post-stroke tongue muscle weakness and optimal treatments have not been established. To advance understanding of physiological mechanisms of post stroke dysphagia, we sought to validate the unilateral transient middle cerebral artery occlusion (MCAO) rat model of ischemic stroke as a translational model of post stroke dysphagia. Our goal was to establish clinically relevant measures and chronicity of functional deficits; criteria that increase the likelihood that findings will translate to the clinic. We hypothesized that MCAO would cause tongue weakness and functional swallowing changes.

METHODS

Maximum voluntary tongue forces and videofluoroscopic swallowing studies were collected in 8-week old male Sprague-Dawley rats prior to receiving either a left MCAO (N = 10) or sham (N = 10) surgery. Tongue forces and VFSS were reassessed at 1 and 8 weeks post-surgery.

RESULTS

Maximum voluntary tongue force, bolus area, and bolus speed were significantly reduced in the MCAO group at the 1 and 8-week timepoints.

CONCLUSION

Clinically relevant changes to swallowing and tongue force support the use of the MCAO rat model as a translational model of post stroke dysphagia. This model will allow for future studies to improve our understanding of the physiology contributing to these functional changes as well as the impact of therapeutic interventions on physiological targets and function.

Mapping acute lesion locations to physiological swallow impairments after stroke

Dysphagia is a common deficit after a stroke, and it is frequently associated with pneumonia, malnutrition, dehydration, and poor quality of life. It is not yet fully clear which brain regions are directly related to swallowing, and how lesions affect swallow physiology. This study aimed to assess the statistical relationship between acute stroke lesion locations and impairment of specific aspects of swallow physiology. We performed lesion symptom mapping with 68 retrospectively recruited, acute, first-ever ischemic stroke patients. Lesions were determined on diffusion weighted MRI scans. Post-stroke swallow physiology was determined using the Modified Barium Swallow Study Impairment Profile (MBSImP©™). The relationship between brain lesion location and 17 physiological aspects of swallowing were tested using voxel-based and region-based statistical associations corrected for multiple comparisons using permutation thresholding. We found that laryngeal elevation, anterior hyoid excursion, laryngeal vestibular closure, and pharyngeal residue were associated with lesioned voxels or regions of interests. All components showed distinct and overlapping lesion locations, mostly in the right hemisphere, and including cortical regions (inferior frontal gyrus, pre- and postcentral gyrus, supramarginal gyrus, angular gyrus, superior temporal gyrus, insula), subcortical regions (thalamus, amygdala) and white matter tracts (superior longitudinal fasciculus, corona radiata, internal capsule, external capsule, ansa lenticularis, lenticular fasciculus). Our findings indicate that different aspects of post-stroke swallow physiology are associated with distinct lesion locations, primarily in the right hemisphere, and primarily including sensory-motor integration areas and their corresponding white matter tracts. Future studies are needed to expand on our findings and thus, support the development of a neuroanatomical model of post-stroke swallow physiology and treatment approaches targeting the neurophysiological underpinnings of swallowing post stroke.

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Different aspects of swallow physiology are associated with distinct stroke lesion locations.

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Sensory-motor integration areas and white matter tracts are crucial for swallow physiology.

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Mostly regions in the right and only few in the left hemisphere contribute to swallow physiology.

Differences in swallow physiology in patients with left and right hemispheric strokes

BACKGROUND

We sought to determine the impact of lesion lateralization and lesion volume on swallow impairment on group-level by comparing patients with left and right hemisphere strokes and on patient-level by analyzing patients individually.

METHODS

We performed a retrospective, observational, cross-sectional study of 46 patients with unilateral (22 left, 24 right), acute, first-ever, ischemic strokes who received a diffusion weighted MRI (DW-MRI) and modified barium swallow study (MBSS) during their acute hospital stay. We determined lesion side on the DW-MRI and measured swallow physiology using the Modified Barium Swallow Impairment Profile (MBSImP™©), Penetration-Aspiration Scale (PAS), swallow timing, distance, area, and speed measures. We performed Pearson's Chi-Square and Wilcoxon Rank-Sum tests to compare patients with left and right hemisphere strokes, and Pearson or Spearman correlation, simple logistic regression, linear, and logistic multivariable regression modeling to assess the relationship between variables.

RESULTS

At the group-level, there were no differences in MBSImP oral swallow impairment scores between patients with left and right hemisphere stroke. In adjusted analyses, patients with right hemisphere strokes showed significantly worse MBSImP pharyngeal total scores (p = 0.02), worse MBSImP component specific scores for laryngeal vestibular closure (Bonferroni adjusted alpha p ≤ 0.0029), and worse PAS scores (p = 0.03). Patients with right hemisphere strokes showed worse timing, distance, area, and speed measures. Lesion volume was significantly associated with MBSImP pharyngeal residue (p = 0.03) and pharyngeal total scores (p = 0.04). At the patient-level, 24% of patients (4 left, 7 right) showed opposite patterns of MBSImP oral and pharyngeal swallow impairment than seen at group-level.

CONCLUSION

Our study showed differences in swallow physiology between patients with right and left unilateral strokes with patients with right hemisphere strokes showing worse pharyngeal impairment. Lesion lateralization seems to be a valuable marker for the severity of swallowing impairment at the group-level but less informative at the patient-level.

Effects of Fluoxetine on Poststroke Dysphagia: A Clinical Retrospective Study

BACKGROUND

To investigate whether fluoxetine improves poststroke dysphagia and to detect the potential relationship between serum brain-derived neurotrophic factor (BDNF) levels and fluoxetine effects.

METHODS

In this retrospective study, 159 stroke patients who met our study criteria were included. In total, 110 patients were placed in the control group, and 49 patients were placed in the fluoxetine group. Demographic and clinical characteristics of the patients were collected for the baseline assessment. Functional independence measure scores and American speech-language-hearing association/functional communication measures scores for swallowing were collected to evaluate the patients' swallowing function. Patients' serums were collected at weeks 1 and 3 after admission, and serum BDNF levels were measured by enzyme-linked immunosorbent assay. T test, chi-squared test, and general linear model analysis were performed to determine the differences between the two groups.

RESULTS

A significantly higher improvement of swallowing function was observed in the fluoxetine group compared with that of the control group (P = .023). In addition, a general linear model analysis showed that the treatment of fluoxetine has a statistically significant effect on swallowing improvement after adjustment of swallowing score on admission, stroke types, and interval between the onset of stroke and admission (P = .022, R² = .46, adjusted R² = .446). There is no significant difference in the change of serum BDNF levels in the two groups (P = .269).

CONCLUSIONS

This study suggests that treatment with fluoxetine in stroke patients with dysphagia may improve swallowing function. A placebo-controlled, randomized clinical trial is warranted to confirm this finding.

NEURAL CONTROL OF SWALLOWING

ABSTRACT BACKGROUND: Swallowing is a motor process with several discordances and a very difficult neurophysiological study. Maybe that is the reason for the scarcity of papers about it. OBJECTIVE: It is to describe the chewing neural control and oral bolus qualification. A review the cranial nerves involved with swallowing and their relationship with the brainstem, cerebellum, base nuclei and cortex was made. METHODS: From the reviewed literature including personal researches and new observations, a consistent and necessary revision of concepts was made, not rarely conflicting. RESULTS AND CONCLUSION: Five different possibilities of the swallowing oral phase are described: nutritional voluntary, primary cortical, semiautomatic, subsequent gulps, and spontaneous. In relation to the neural control of the swallowing pharyngeal phase, the stimulus that triggers the pharyngeal phase is not the pharyngeal contact produced by the bolus passage, but the pharyngeal pressure distension, with or without contents. In nutritional swallowing, food and pressure are transferred, but in the primary cortical oral phase, only pressure is transferred, and the pharyngeal response is similar. The pharyngeal phase incorporates, as its functional part, the oral phase dynamics already in course. The pharyngeal phase starts by action of the pharyngeal plexus, composed of the glossopharyngeal (IX), vagus (X) and accessory (XI) nerves, with involvement of the trigeminal (V), facial (VII), glossopharyngeal (IX) and the hypoglossal (XII) nerves. The cervical plexus (C1, C2) and the hypoglossal nerve on each side form the ansa cervicalis, from where a pathway of cervical origin goes to the geniohyoid muscle, which acts in the elevation of the hyoid-laryngeal complex. We also appraise the neural control of the swallowing esophageal phase. Besides other hypotheses, we consider that it is possible that the longitudinal and circular muscular layers of the esophagus display, respectively, long-pitch and short-pitch spiral fibers. This morphology, associated with the concept of energy preservation, allows us to admit that the contraction of the longitudinal layer, by having a long-pitch spiral arrangement, would be able to widen the esophagus, diminishing the resistance to the flow, probably also by opening of the gastroesophageal transition. In this way, the circular layer, with its short-pitch spiral fibers, would propel the food downwards by sequential contraction.

Clinical Effects and Differences in Neural Function Connectivity Revealed by MRI in Subacute Hemispheric and Brainstem Infarction Patients With Dysphagia After Swallowing Therapy

Background: Early detection and intervention for post-stroke dysphagia could reduce the incidence of pulmonary complications and mortality. The aims of this study were to investigate the benefits of swallowing therapy in swallowing function and brain neuro-plasticity and to explore the relationship between swallowing function recovery and neuroplasticity after swallowing therapy in cerebral and brainstem stroke patients with dysphagia.

Methods: We collected 17 subacute stroke patients with dysphagia (11 cerebral stroke patients with a median age of 76 years and 6 brainstem stroke patients with a median age of 70 years). Each patient received swallowing therapies during hospitalization. For each patient, functional oral intake scale (FOIS), functional dysphagia scale (FDS) and 8-point penetration-aspiration scale (PAS) in videofluoroscopy swallowing study (VFSS), and brain functional magnetic resonance imaging (fMRI) were evaluated before and after treatment.

Results: FOIS (p = 0.003 in hemispheric group and p = 0.039 in brainstem group) and FDS (p = 0.006 in hemispheric group and p = 0.028 in brainstem group) were both significantly improved after treatment in hemispheric and brainstem stroke patients. In hemispheric stroke patients, changes in FOIS were related to changes of functional brain connectivity in the ventral default mode network (vDMN) of the precuneus in brain functional MRI (fMRI). In brainstem stroke patients, changes in FOIS were related to changes of functional brain connectivity in the left sensorimotor network (LSMN) of the left postcentral region characterized by brain fMRI.

Conclusion: Both hemispheric and brainstem stroke patients with different swallowing difficulties showed improvements after swallowing training. For these two dysphagic stroke groups with corresponding etiologies, swallowing therapy could contribute to different functional neuroplasticity.

Dual Transcranial Direct Current Stimulation for Poststroke Dysphagia: A Randomized Controlled Trial

BACKGROUND

Poststroke dysphagia is associated with considerable morbidity and has high health care cost implications.

OBJECTIVE

To evaluate whether anodal transcranial direct current stimulation (tDCS) over the lesioned hemisphere and cathodal tDCS to the contralateral one during the early stage of rehabilitation can improve poststroke dysphagia.

METHODS

A total of 40 patients referred to our neurorehabilitation department were randomized to receive anodal tDCS over the damaged hemisphere plus cathodal stimulation over the contralateral one versus sham stimulation during swallowing maneuvers over the course of 10 sessions of treatment. Swallowing function was evaluated before and after stimulation using the Dysphagia Outcome and Severity Scale (DOSS).

RESULTS

The percentage of patients who reached various thresholds of improvement was higher in the tDCS group than in the sham group, but the differences were not significant (eg, DOSS score ≥ 20% increase from baseline: 55% in the tDCS group vs 40% in the sham group; P = .53). Among all variables recorded at baseline, only a subgroup of patients without nasogastric tube showed a significantly higher improvement with tDCS treatment versus sham (DOSS score ≥10% and ≥20% from baseline: 64.29% vs 0%, P = .01).

CONCLUSIONS

In patients with poststroke dysphagia, treatment with dual tDCS in the early phase of rehabilitation does not significantly increase the probability of recovery compared with sham stimulation.

Early Screening Parameters for Dysphagia in Acute Ischemic Stroke

BACKGROUND

Dysphagia is a frequent symptom in patients with acute stroke. It is associated with malnutrition, aspiration and mortality. The identification of early screening parameters for dysphagia promptly leading to a professional swallowing examination is therefore of utmost importance. This study aimed to detect early and easily assessable predictors of dysphagia in a large cohort of patients with acute ischemic stroke.

METHODS

Our analysis was based on data from a prospective in-hospital registry. Patients with ischemic stroke were included over the course of 3 years. Patients were scheduled to undergo a clinical swallowing investigation within the first 24 h after hospital admission. Step-wise multivariate logistic regression was used to identify independent predictors of dysphagia in general and of pneumonia in particular.

RESULTS

1,646 patients with ischemic stroke were included. Stroke severity in terms of higher National Institute of Health Stroke Scale (NIHSS) values (p < 0.001), male gender (p = 0.006) and higher age (p < 0.001) independently predicted dysphagia. A receiver operating characteristics analysis revealed an NIHSS cut-off value of 4.5 for optimal differentiation between patients with and without dysphagia (sensitivity 0.77; specificity 0.77). Dysphagia (p < 0.001), male gender (p = 0.002), higher NIHSS scores (p < 0.001) and higher age (p = 0.002) were factors that were independently associated with pneumonia. The NIHSS cut-off value for differentiating between patients with and without pneumonia was 5.5 (sensitivity 0.91; specificity 0.67).

CONCLUSIONS

Stroke severity in terms of NIHSS is a simple and reliable predictor of dysphagia. Patients with NIHSS values ≥5 should be quickly directed towards a professional swallowing examination. Dysphagia was confirmed to be a strong predictor of pneumonia.

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.

Normalization of Temporal Aspects of Swallowing Physiology after the McNeill Dysphagia Therapy Program

Objectives

We examined the timing of physiological swallowing events in patients before and after completion of an exercise-based dysphagia intervention (McNeill Dysphagia Therapy Program; MDTP) and compared their performance to that of healthy volunteers.

Methods

Eight adults (mean age, 57.5 years) with chronic dysphagia (mean, 45 months) completed 3 weeks of the MDTP. Before and after the MDTP we measured lingual-palatal and pharyngeal manometric pressures during swallows of thin liquid, thick liquid, and pudding material in 5-mL volumes. Using the pressure peak of the pharyngoesophageal segment clearing wave as the anchor point, we measured the relative timing of pressure peaks from the anterior, middle, and posterior parts of the tongue and the manometric peaks from the base of the tongue, the hypopharynx, and the nadir of the pharyngoesophageal segment. We compared these results to identical measures obtained from 34 healthy adults (mean age, 44.0 years).

Results

The timing of physiological events before the MDTP was significantly slower than that of the group of healthy volunteers. The timing data from after the MDTP were not significantly different from those of the healthy group. The magnitude change was greatest for thin liquid.

Conclusions

Dysphagia therapy with the MDTP improves the timing of physiological events during swallowing. Temporal coordination of swallowing components after therapy approximates that of healthy adults, suggesting a normalization of swallow timing after the MDTP.

Effect of transcranial direct current stimulation on swallowing apraxia and cortical excitability in stroke patients

BACKGROUND

Swallowing apraxia is characterized by impaired volitional swallowing but relatively preserved reflexive swallowing. Few studies are available on the effectiveness of behavioral therapy and management of the condition.

OBJECTIVE

This study aimed to investigate the effect of transcranial direct current stimulation (tDCS) on swallowing apraxia and cortical activation in stroke patients.

METHODS

The study included three inpatients (age 48-70 years; 1 male, 2 females; duration of stroke, 35-55 d) with post-stroke swallowing apraxia and six age-matched healthy subjects (age 45-65 years; 3 males, 3 females). Treatments were divided into two phases: Phase A and Phase B. During Phase A, the inpatients received three weeks of sham tDCS and conventional treatments. During Phase B, these patients received three weeks of anodal tDCS over the bilateral primary sensorimotor cortex (S₁M₁) of swallowing and conventional treatments. Swallowing apraxia assessments were measured in three inpatients before Phase A, before Phase B, and after Phase B. The electroencephalography (EEG) nonlinear index of approximate entropy (ApEn) was calculated for three patients and six healthy subjects.

RESULTS

After tDCS, scores of swallowing apraxia assessments increased, and ApEn indices increased in both stimulated and non-stimulated areas.

CONCLUSIONS

Anodal tDCS might provide a useful means for recovering swallowing apraxia, and the recovery could be related to increased excitability of the swallowing cortex. Further investigations should explore the relationship between lesion size and/or lesion site and the prognosis of swallowing apraxia. Clinical trial registry: http://www.chictr.org Registration Number: ChiCTR-TRC-14004955.

Diverging lesion and connectivity patterns influence early and late swallowing recovery after hemispheric stroke

Knowledge about the recovery of oral intake after hemispheric stroke is important to guide therapeutic decisions, including the administration of enteral tube feeding and the choice of the appropriate feeding route. They aimed to determine the localization and connectivity of lesions in impaired recovery versus recovered swallowing after initially dysphagic stroke. Sixty-two acute ischemic hemispheric stroke patients with impaired oral intake were included in a prospective observational cohort study. Voxel-based lesion-symptom mapping and probabilistic tractography were used to determine the association of lesion location and connectivity with impaired recovery of oral intake ≥7 days (indication for early tube feeding) and ≥4 weeks (indication for percutaneous endoscopic gastrostomy feeding) after stroke. Two distinct patterns influencing recovery of swallowing were recognized. Firstly, impaired recovery of oral intake after ≥7 days was significantly associated with lesions of the superior corona radiata (65% of statistical map, P < 0.05). The affected fibers were connected with the thalamus, primary motor, and supplemental motor areas and the basal ganglia. Secondly, impaired recovery of oral intake after ≥4 weeks significantly correlated with lesions of the anterior insula (54% of statistical map, P < 0.05), which was connected to adjacent operculo-insular areas of deglutition. These findings indicate that early swallowing recovery is influenced by white matter lesions disrupting thalamic and corticobulbar projection fibers. Late recovery is determined by specific cortical lesions affecting association fibers. This knowledge may help clinicians to identify patients at risk of prolonged swallowing problems that would benefit from enteral tube feeding. Hum Brain Mapp 38:2165-2176, 2017. © 2017 Wiley Periodicals, Inc.

Brain imaging correlates of recovered swallowing after dysphagic stroke: A fMRI and DWI study

Neurogenic dysphagia frequently occurs after stroke and deglutitive aspiration is one of the main reasons for subacute death after stroke. Although promising therapeutic interventions for neurogenic dysphagia are being developed, the functional neuroanatomy of recovered swallowing in this population remains uncertain. Here, we investigated 18 patients post-stroke who recovered from dysphagia using an event related functional magnetic resonance imaging (fMRI) study of swallowing. Patients were characterized by initial dysphagia score (mild to severe), lesion mapping, white matter fractional anisotropy (FA) of the pyramidal tracts, and swallowing performance measurement during fMRI scanning. Eighteen age matched healthy participants served as a control group. Overall, patients showed decreased fMRI-activation in the entire swallowing network apart from an increase of activation in the contralesional primary somatosensory cortex (S1). Moreover, fMRI activation in contralesional S1 correlated with initial dysphagia score. Finally, when lesions of the pyramidal tract were more severe, recovered swallowing appeared to be associated with asymmetric activation of the ipsilesional anterior cerebellum. Taken together, our data support a role for increased contralesional somatosensory resources and ipsilesional anterior cerebellum feed forward loops for recovered swallowing after dysphagia following stroke.

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Recovered dysphagic stroke patients showed decreased fMRI-activation of swallowing network.

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Contralesional S1 activation was higher in patient vs. control group and positively associated with initial dysphagia score.

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Ipsilesional anterior cerebellum was asymmetrically activated with severe lesions of pyramidal tract.

Post-stroke dysphagia: A review and design considerations for future trials

Post-stroke dysphagia (a difficulty in swallowing after a stroke) is a common and expensive complication of acute stroke and is associated with increased mortality, morbidity, and institutionalization due in part to aspiration, pneumonia, and malnutrition. Although most patients recover swallowing spontaneously, a significant minority still have dysphagia at six months. Although multiple advances have been made in the hyperacute treatment of stroke and secondary prevention, the management of dysphagia post-stroke remains a neglected area of research, and its optimal management, including diagnosis, investigation and treatment, have still to be defined.

Repetitive Transcranial Magnetic Stimulation: a Novel Approach for Treating Oropharyngeal Dysphagia

In recent years, repetitive transcranial magnetic stimulation, a technique used to produce human central neurostimulation, has attracted increased interest and been applied experimentally in the treatment of dysphagia. This review presents a synopsis of the current research for the application of repetitive transcranial magnetic stimulation (rTMS) on dysphagia. Here, we review the mechanisms underlying the effects of rTMS and the results from studies on both healthy volunteers and dysphagic patients. The clinical studies on dysphagia have primarily focussed on dysphagia post-stroke. We discuss why it is difficult to draw conclusions for the efficacy of this neurostimulation technique, given the major differences between studies. The intention here is to stimulate potential research questions not yet investigated for the application of rTMS on dysphagic patients prior to their translation into clinical practice for dysphagia rehabilitation.

Effects of non-invasive brain stimulation on post-stroke dysphagia: A systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

The primary aim of this review is to evaluate the effects of non-invasive brain stimulation on post-stroke dysphagia.

METHODS

Thirteen databases were systematically searched through July 2014. Studies had to meet pre-specified inclusion and exclusion criteria. Each study's methodological quality was examined. Effect sizes were calculated from extracted data and combined for an overall summary statistic.

RESULTS

Eight randomized controlled trials were included. These trials revealed a significant, moderate pooled effect size (0.55; 95% CI=0.17, 0.93; p=0.004). Studies stimulating the affected hemisphere had a combined effect size of 0.46 (95% CI=-0.18, 1.11; p=0.16); studies stimulating the unaffected hemisphere had a combined effect size of 0.65 (95% CI=0.14, 1.16; p=0.01). At long-term follow up, three studies demonstrated a large but non-significant pooled effect size (0.81, p=0.11).

CONCLUSIONS

This review found evidence for the efficacy of non-invasive brain stimulation on post-stroke dysphagia. A significant effect size resulted when stimulating the unaffected rather than the affected hemisphere. This finding is in agreement with previous studies implicating the plasticity of cortical neurons in the unaffected hemisphere.

SIGNIFICANCE

Non-invasive brain stimulation appears to assist cortical reorganization in post-stroke dysphagia but emerging factors highlight the need for more data.

Functional magnetic resonance and swallowing: critical literature review

Introduction

Aspects of the neuroanatomical representation of swallowing have been investigated in humans through brain mapping techniques, such as functional magnetic resonance imaging (fMRI).

Objective

This critical qualitative review of the literature analyzed international scientific publications in the PubMed database that investigated the activation of the central nervous system in humans during the act of swallowing.

Methods

This investigation was limited to articles that investigated adults older than 18 years, published in English or Portuguese, between January 2002 and December 2013. Publications that did not have access to the full text, that were repeated by overlapping keywords, case studies, literature reviews, letters to the editor, and those not directly related to the topic of the investigation were excluded.

Results

A total of 649 articles were identified, of which 21 matched the inclusion criteria.

Conclusion

The main purpose of the manuscripts that investigate the swallowing process through fMRI were: to characterize swallowing in different pathologies; to compare swallowing in different age groups; to describe brain activation in different stimulation conditions. These studies indicate multiple cortical regions involved in swallowing control. Overall, the studies indicate that fMRI is a non-invasive and quantitative method that allows the investigation of characteristics that are quite often not clinically visible.

fMRI and MRS measures of neuroplasticity in the pharyngeal motor cortex

INTRODUCTION

Paired associative stimulation (PAS), is a novel non-invasive technique where two neural substrates are employed in a temporally coordinated manner in order to modulate cortico-motor excitability within the motor cortex (M1). In swallowing, combined pharyngeal electrical and transcranial-magnetic-stimulation induced beneficial neurophysiological and behavioural effects in healthy subjects and dysphagic stroke patients. Here, we aimed to investigate the whole-brain changes in neural activation during swallowing using functional magnetic resonance imaging (fMRI) following PAS application and in parallel assess associated GABA changes with magnetic resonance spectroscopy (MRS).

METHODS

Healthy adults (n=11, 38±9years old) were randomised to receive real and sham PAS to the 'stronger' motor cortex pharyngeal representation, on 2 separate visits. Following PAS, event-related fMRI was performed to assess changes in brain activation in response to water and saliva swallowing and during rest. Data were analysed (SPM8) at P<.001. MRS data were acquired using MEGA-PRESS before and after the fMRI acquisitions on both visits and GABA concentrations were measured (AMARES, jMRUI).

RESULTS

Following real PAS, BOLD signal changes (group analyses) increased at the site of stimulation during water and saliva swallowing, compared to sham PAS. It is also evident that PAS induced significant increases in BOLD signal to contralateral (to stimulation) hemispheric areas that are of importance to the swallowing neural network. Following real PAS, GABA:creatine ratio showed a trend to increase contralateral to PAS.

CONCLUSION

Targeted PAS applied to the human pharyngeal motor cortex induces local and remote changes in both primary and non-primary areas for water and saliva tasks. There is a possibility that changes of the inhibitory neurotransmitter, GABA, may play a role in the changes in BOLD signal. These findings provide evidence for the mechanisms underlying the beneficial effects of PAS on the brain swallowing network.

Compensatory recombination phenomena of neurological functions in central dysphagia patients

We speculate that cortical reactions evoked by swallowing activity may be abnormal in patients with central infarction with dysphagia. The present study aimed to detect functional imaging features of cerebral cortex in central dysphagia patients by using blood oxygen level-dependent functional magnetic resonance imaging techniques. The results showed that when normal controls swallowed, primary motor cortex (BA4), insula (BA13), premotor cortex (BA6/8), supramarginal gyrus (BA40), and anterior cingulate cortex (BA24/32) were activated, and that the size of the activated areas were larger in the left hemisphere compared with the right. In recurrent cerebral infarction patients with central dysphagia, BA4, BA13, BA40 and BA6/8 areas were activated, while the degree of activation in BA24/32 was decreased. Additionally, more areas were activated, including posterior cingulate cortex (BA23/31), visual association cortex (BA18/19), primary auditory cortex (BA41) and parahippocampal cortex (BA36). Somatosensory association cortex (BA7) and left cerebellum in patients with recurrent cerebral infarction with central dysphagia were also activated. Experimental findings suggest that the cerebral cortex has obvious hemisphere lateralization in response to swallowing, and patients with recurrent cerebral infarction with central dysphagia show compensatory recombination phenomena of neurological functions. In rehabilitative treatment, using the favorite food of patients can stimulate swallowing through visual, auditory, and other nerve conduction pathways, thus promoting compensatory recombination of the central cortex functions.

Study design for the fostering eating after stroke with transcranial direct current stimulation trial: a randomized controlled intervention for improving Dysphagia after acute ischemic stroke

GOAL

Dysphagia is a major stroke complication but lacks effective therapy that can promote recovery. Noninvasive brain stimulation with and without peripheral sensorimotor activities may be an attractive treatment option for swallowing recovery but has not been systematically investigated in the stroke population. This article describes the study design of the first prospective, single-center, double-blinded trial of anodal versus sham transcranial direct current stimulation (tDCS) used in combination with swallowing exercises in patients with dysphagia from an acute ischemic stroke. The aim of this study is to gather safety data on cumulative sessions of tDCS in acute-subacute phases of stroke, obtain information about effects of this intervention on important physiologic and clinically relevant swallowing parameters, and examine possible dose effects.

METHODS

Ninety-nine consecutive patients with dysphagia from an acute unilateral hemispheric infarction with a Penetration and Aspiration Scale (PAS) score of 4 or more and without other confounding reasons for dysphagia will be enrolled at a single tertiary care center. Subjects will be randomized to either a high or low dose tDCS or a sham group and will undergo 10 sessions over 5 consecutive days concomitantly with effortful swallowing maneuvers. The main efficacy measures are a change in the PAS score before and after treatment; the main safety measures are mortality, seizures, neurologic, motor, and swallowing deterioration.

CONCLUSIONS

The knowledge gained from this study will help plan a larger confirmatory trial for treating stroke-related dysphagia and advance our understanding of important covariates influencing swallowing recovery and response to the proposed intervention.

Mapping (and modeling) physiological movements during EEG-fMRI recordings: the added value of the video acquired simultaneously

BACKGROUND

During resting-state EEG-fMRI studies in epilepsy, patients' spontaneous head-face movements occur frequently. We tested the usefulness of synchronous video recording to identify and model the fMRI changes associated with non-epileptic movements to improve sensitivity and specificity of fMRI maps related to interictal epileptiform discharges (IED).

NEW METHODS

Categorization of different facial/cranial movements during EEG-fMRI was obtained for 38 patients [with benign epilepsy with centro-temporal spikes (BECTS, n=16); with idiopathic generalized epilepsy (IGE, n=17); focal symptomatic/cryptogenic epilepsy (n=5)]. We compared at single subject- and at group-level the IED-related fMRI maps obtained with and without additional regressors related to spontaneous movements. As secondary aim, we considered facial movements as events of interest to test the usefulness of video information to obtain fMRI maps of the following face movements: swallowing, mouth-tongue movements, and blinking.

RESULTS

Video information substantially improved the identification and classification of the artifacts with respect to the EEG observation alone (mean gain of 28 events per exam).

COMPARISON WITH EXISTING METHOD

Inclusion of physiological activities as additional regressors in the GLM model demonstrated an increased Z-score and number of voxels of the global maxima and/or new BOLD clusters in around three quarters of the patients. Video-related fMRI maps for swallowing, mouth-tongue movements, and blinking were comparable to the ones obtained in previous task-based fMRI studies.

CONCLUSIONS

Video acquisition during EEG-fMRI is a useful source of information. Modeling physiological movements in EEG-fMRI studies for epilepsy will lead to more informative IED-related fMRI maps in different epileptic conditions.

Pharyngeal electrical stimulation can modulate swallowing in cortical processing and behavior - magnetoencephalographic evidence

BACKGROUND

The act of swallowing is a complex neuromuscular function that is processed in a distributed network involving cortical, subcortical and brainstem structures. Difficulty in swallowing arises from a variety of neurologic diseases for which therapeutic options are currently limited. Pharyngeal electrical stimulation (PES) is a novel intervention designed to promote plastic changes in the pharyngeal motor cortex to aid dysphagia rehabilitation. In the present study we evaluate the effect of PES on cortical swallowing network activity and associated changes in swallowing performance.

METHODS

In a randomized, crossover study design 10min of real (0.2-ms pulses, 5Hz, 280V, stimulation intensity at 75% of maximum tolerated threshold) or sham PES were delivered to 14 healthy volunteers in two separate sessions. Stimulation was delivered via a pair of bipolar ring electrodes mounted on an intraluminal catheter positioned in the pharynx. Before and after each intervention swallowing capacity (ml/s) was tested using a 150ml-water swallowing stress test. Event-related desynchronization (ERD) of cortical oscillatory activity during volitional swallowing was recorded applying whole-head magnetoencephalography before, immediately after and 45min past the intervention.

RESULTS

A prominent reduction of ERD in sensorimotor brain areas occurred in the alpha and beta frequency ranges immediately after real PES but not after sham stimulation (p<0.05) and had faded after 45min. Volume per swallow and swallowing capacity significantly increased following real stimulation only.

CONCLUSION

Attenuation of ERD following PES reflects stimulation-induced increased swallowing processing efficiency, which is associated with subtle changes in swallowing function in healthy subjects. Our data contribute evidence that swallowing network organization and behavior can effectively be modulated by PES.

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.