Swallowing physiology of sequential straw drinking

The goal of this study was to examine deglutitive physiology during sequential straw drinking in healthy young adults (n = 15) to learn how sequential swallowing differs from single swallows. The physiology of single swallows has been studied extensively in healthy adults and in adults with a variety of debilitating conditions, but the physiology of sequential swallows has not been studied adequately. Videofluoroscopic analysis revealed three distinct patterns of hyolaryngeal complex (HLC) movement during sequential straw swallows: opening of the laryngeal vestibule after each swallow (Type I, 53%), continued vestibule closure after each swallow (Type II, 27%), and interchangeable vestibule opening and closing during the swallow sequence (Mixed, 20%). Unlike discrete swallowing, the onset of the pharyngeal swallow occurred when the bolus was inferior to the valleculae in the majority of subjects and was significantly associated with HLC movement pattern. The leading bolus edge was inferior to the valleculae at swallow onset for Type II movement patterns. For Type I movement patterns, bolus position at swallow onset was randomly distributed between three anatomical positions: superior to the valleculae, at the level of the valleculae, and inferior to the valleculae. Preswallow pharyngeal bolus accumulation, which is common during mastication, was evident and significantly associated with the HLC pattern of opened laryngeal vestibule after each swallow. These data suggest that in healthy young adults, sequential swallows differ physiologically from discrete swallows and indicate substantial variability in deglutitive biomechanics.

Optimal patterns of care for dysphagic stroke patients

Dysphagia is a common poststroke occurrence. It is associated with aspiration, pneumonia, and malnutrition and can persist in some patients. Prompt evaluation and treatment are crucial to prevent ensuing medical problems. This article reviews the current best practices in clinical and dynamic deglutitive evaluations, including screening methods for identification of stroke patients at risk for dysphagia and aspiration. Optimal patterns of care in the management and treatment of the dysphagic stroke patient are also discussed.

Praxis lateralization: errors in right and left hemisphere stroke

Whereas the representations of skilled movements in most right handers are stored in the left hemisphere, the right hemisphere's contribution to action planning remains unclear. We investigated error patterns in left (LHD) and right hemisphere damaged (RHD) subjects as well as normal control subjects (C) to determine if specific components of action programs may be processed by the right hemisphere or bilaterally represented. We had these subjects perform gestures to verbal command with the ipsilesional limb. Although the LHD group made significantly more qualitative errors than the C and RHD groups, the RHD subjects produced a number of apraxic errors. Specifically, the LHD group produced a wide range of spatiotemporal and conceptual errors for both transitive and intransitive gestures, while the RHD group made specific spatial and temporal errors primarily when performing transitive gestures. These findings support the postulate that the left hemisphere stores the spatiotemporal and conceptual representations of learned skilled movements, while several specific components of action programs, such as external configuration (limb orientation) and timing, may have bihemispheric representations.

Swallowing apraxia: a disorder of the Praxis system?

The purpose of this review is to evaluate the disorder of swallowing apraxia and determine how it fits into the praxis system. Swallowing apraxia, a proposed disorder of lingual, labial, and mandibular coordination, has been observed before bolus transfer during the oral stage of swallowing. Although frequently discussed anecdotally in dysphagia literature, the possible mechanisms and neural networks of swallowing apraxia have not been elucidated. Similarities and differences of swallowing apraxia with buccofacial, speech, and limb apraxias are evident. Critical review of the literature has identified possible similarities as greater occurrence upon command, transitive nature of the action, and evidence of spatial errors. Conversely, differences such as hemispheric lateralization and multiple gesture assessment may exist between swallowing apraxia and more traditional forms of apraxia. Until discrete error patterns of swallowing apraxia are identified and precisely measured, the nature of this disorder and its relationship with the praxis system will continue to remain elusive.

Clinical predictors of dysphagia and aspiration risk: outcome measures in acute stroke patients

OBJECTIVE

To use an established dysphagia clinical screening system to evaluate outcomes in acute stroke patients.

DESIGN

Case-control study.

SETTING

Tertiary care center.

PARTICIPANTS

Acute stroke patients (n = 56) consecutively referred to a speech pathology service.

MAIN OUTCOME MEASURES

Outcomes (ie, pneumonia, dietary status at discharge) in patients who were referred for a videofluoroscopic swallow study (VSS) based on results of a previously validated clinical screening system were compared with outcomes in patients who were not referred for VSS based on the clinical evaluation.

RESULTS

Thirty-eight of 56 patients (68%) presented with 2 or more clinical predictors of moderate to severe dysphagia and were further evaluated with VSS, whereas 18 patients (32%) had fewer than 2 clinical features and were not evaluated radiographically. Based on patient outcomes and VSS results, identification of at least 2 clinical predictors significantly distinguished patients with moderate to severe dysphagia from patients with mild dysphagia or normal swallowing. None of the patients in either group developed pneumonia while following recommendations of the clinical or dynamic swallowing evaluation, and 93% of the patients returned to a regular diet.

CONCLUSIONS

These data demonstrate that clinical use of this screening system can objectively identify acute stroke patients who warrant further diagnostic studies and can safely determine which patients need no further deglutitive evaluation.

Lesion localization in acute stroke patients with risk of aspiration

The objective of this prospective study was to determine whether specific neuroanatomical sites were associated with increased risk of aspiration in acute stroke patients. Videofluoroscopic swallow studies (VSS) and computed tomography or magnetic resonance imaging scans were completed on consecutive male stroke patients (n = 54). Videofluoroscopic swallow studies were scored on a scale from 0 (normal swallowing) to 4 (severe dysphagia). Patients with scores of 0-1 were grouped together as having no risk of aspiration, and patients with scores of 2-4 were grouped together as having a risk of aspiration. Lesion analyses revealed that location appeared to be more critical than hemisphere or lesion size in predicting patients at risk of aspiration. Anterior locations and subcortical periventricular white matter sites were commonly lesioned in patients with risk of aspiration, whereas patients without risk of aspiration were more likely to have posterior lesions and lesions to subcortical gray matter structures. These data demonstrate that swallowing appears to be mediated by a distributed neural network that involves both cerebral hemispheres with descending input to the medulla; however, specific lesion locations may put patients at a greater risk of aspiration.

Lingual discoordination and dysphagia following acute stroke: analyses of lesion localization

The mechanism and neural substrates that mediate lingual coordination during swallowing have not been well characterized. Although lingual discoordination during swallowing has been difficult to quantify, it has been defined as the random disorganization of anterior-posterior tongue movements evident in bolus propulsion. In a sample of consecutive acute stroke patients (n = 59), videofluoroscopic evaluation showed a 19% incidence of lingual discoordination during swallowing. Lingual discoordination during swallowing was not commonly associated with buccofacial apraxia, apraxia of speech, nor limb apraxia. Hemisphere and anterior-posterior localization did not predict occurrence of lingual discoordination. Lingual discoordination during swallowing occurred commonly in patients with subcortical lesions with the periventricular white matter (PVWM), the most common site of involvement. PVWM lesions may disconnect anterior and posterior cortical regions that are critical to oral control and coordination in swallowing, thereby producing lingual discoordination during swallowing. These data also suggest that the neural mechanisms that mediate lingual coordination may at least in part be independent of the neural systems that mediate buccofacial, limb, and speech praxis functions.

Persistent dysphagia and dysphonia following cervical spine surgery

Persistent dysphagia and dysphonia following anterior cervical spine surgery have been underdiagnosed. Understanding the physiologic mechanism resulting in post-surgical dysphagia and dysphonia is essential to providing appropriate treatment. Two cases of protracted dysphagia and dysphonia following left anterior cervical corpectomy were reviewed. Videofluoroscopic evaluation, videostroboscopic assessment and laryngeal nerve-conduction testing were used to determine swallowing, vocal fold and cranial nerve integrity; to assess the ability to achieve oral nutrition; and to direct therapy and surgical procedures to improve swallowing and voice. With a multidisciplinary approach, the physiologic problems of post-surgical dysphagia and dysphonia can be addressed and therapeutic and/or surgical treatments initiated promptly.

Aspiration in patients with acute stroke

OBJECTIVES

To determine the frequency and clinical predictors of aspiration within 5 days of acute stroke.

DESIGN

Case series.

SETTING

Tertiary care center.

PATIENTS

Consecutive stroke patients (n = 55) with new neurologic deficit evaluated within 5 days of acute stroke.

MAIN OUTCOME MEASURES

Comparison of features identified on clinical swallowing and oromotor examinations and occurrence of aspiration (silent or overt) evident on videofluoroscopic swallow study (VSS).

RESULTS

Aspiration occurred in 21 of 55 patients (38%). Whereas 7 of 21 patients (33%) aspirated overtly, 14 (67%) aspirated silently on VSS. Chi-square analyses revealed that dysphonia, dysarthria, abnormal gag reflex, abnormal volitional cough, cough after swallow, and voice change after swallow were significantly related to aspiration and were predictors of the subset of patients with silent aspiration. Logistic regression revealed that abnormal volitional cough and cough with swallow, in conjunction, predicted aspiration with 78% accuracy.

CONCLUSIONS

Silent aspiration appears to be a significant problem in acute stroke patients because silent aspiration occurred in two thirds of the patients who aspirated. The prediction of patients at risk for aspiration was significantly improved by the presence of concurrent findings of abnormal volitional cough and cough with swallow on clinical examination.

The role of the insular cortex in dysphagia

Recent data indicate that dysphagia may occur following unilateral cortical stroke; however, the elucidation of specific cytoarchitectonic sites that produce deglutition disorders remains unclear. In a previous study of unilateral cortical stroke patients with dysphagia, Daniels et al. proposed that the insula may be important in swallowing as it was the most common lesion site in the patients studied. Therefore, 4 unilateral stroke patients with discrete lesions of the insular cortex were studied to further facilitate understanding of the role of the insula in swallowing. Dysphagia, as confirmed by videofluoroscopy, was evident in 3 of the 4 patients; all had lesions that involved the anterior insula, whereas the only patient without dysphagia had a lesion restricted to the posterior insula. These data suggest that the anterior insula may be an important cortical substrate in swallowing. The anterior insula has connections to the primary and supplementary motor cortices, the ventroposterior medial nucleus of the thalamus, and to the nucleus tractus solitarius, all of which are important regions in the mediation of oropharyngeal swallowing. Therefore, discrete lesions of the anterior insula may disrupt these connections and, thereby, produce dysphagia.

Lesion site in unilateral stroke patients with dysphagia

The purpose of this retrospective study was to elucidate specific lesion sites associated with deglutition disorders by studying unilateral left- and right-hemispheric stroke patients with dysphagia. We reviewed computed tomography and magnetic resonance imaging scans and videofluoroscopic swallow studies of 16 consecutive patients with unilateral ischemic infarcts and dysphagia. Results suggest that unilateral hemispheric lesions may produce dysphagia and that patients with left- and right-hemispheric strokes may have different dysphagia characteristics. Although right-hemispheric lesions were significantly smaller than left-hemispheric lesions, dysphagia seemed to be clinically more significant in patients with right-hemispheric strokes, because a higher incidence of delayed pharyngeal swallow (consistency specific) and pharyngeal stasis was recorded in this population. Cytoarchitectonic lesion mapping showed that the insular cortex was the commonest lesion site, suggesting that the insula may be important in swallowing. A prospective double-blind study in a larger sample of unilateral stroke patients with and without dysphagia is warranted to confirm these preliminary findings.