Abstract
Swallowing problems (dysphagia) following stroke are common and occur more frequently in older people. This article first presents a brief overview of the incidence and prevalence of dysphagia poststroke, the presence of aspiration, its effect on morbidity, and the effects of aging on swallowing. Thereafter, a review of current trends in the evaluation of dysphagia is given, including bedside swallow assessments, videofluoroscopy, and pulse oximetry. A review of treatment strategies employed by speech and language therapists is given together with the evidence (or lack of it) for such strategies.
SWALLOWING PROBLEMS (dysphagia) are common after stroke. However, the exact prevalence of dysphagia, aspiration (abnormal entry of material below the level of the true vocal cords), and silent aspiration (abnormal entry of material below the level of the true vocal cords without outward sign of distress, for example cough or change in vocal quality) is difficult to report accurately, since studies differ in selection criteria, methodology, and the timing of assessment poststroke. 1-12 Older patients have a higher mortality rate and a significantly longer hospital stay. 13 The prevalence of swallowing difficulty increases with normal aging 14 partly because of the increasing prevalence of structural changes in the "swallowing apparatus." 15 A multiplicity of age-related changes in swallowing function has been described. 14-21 Muscle strength and endurance (including that of the tongue) declines with age. Poor leads to problems of mastication. Atrophy of the alveolar margin may lead to poorly fitting dentures.
Nilsson and colleagues 19 found inspiration rather than expiration after swallowing was more common in the elderly with the risk of laryngeal penetration. There is a clear decline with age in both swallowing function and the average volume per swallow. 20 Age-related changes, however, do appear to be subclinical and are not considered to be disorders because the effects on swallowing are negligible and usually only detected during controlled investigations. 16 A person's general health seems to determine the presence and severity of swallowing problems. With acute illness leading to general weakness the elderly lose the ability to compensate. 21 Acute illness may therefore cause temporary dysphagia, especially in the patients over 80. Particular medications and interactions of medications may have an effect on swallowing ability. A detailed drug history is therefore vital since a number of drugs can impair oropharyngeal functioning, often resulting in xerostomia (mouth dryness), thus making swallowing difficult. Included in the medications causing xerostomia are certain anticholinergics, antihypertensives, antihistamines, antipsychotics, anticonvulsants, and tricyclic antidepressants. Some antidepressant medications may also slow swallow coordination and increase the severity of the swallowing disorder. 15
As with the reporting of prevalence of dysphagia poststroke there are difficulties in reporting the exact numbers of patients suffering from malnutrition. However, the reported frequency has varied between 8% and 40%. 22-25 There is variation between clinicians and between hospitals in the timing of feeding patients after stroke and in the form of that feeding, especially if patients remain drowsy or are making a rapid, spontaneous recovery. Patients may be given nothing by mouth or may receive oral fluid and/or diet in a modified form. However, patients often fail to meet their nutritional requirements. A nasogastric (NG) tube is often inserted as the initial form of alternative and/or supplementary feeding. These are, however, rarely successful in the medium/long term. Some clinicians prefer to use a percutaneous endoscopic gastrostomy (PEG), especially if dysphagic symptoms are persisting. There are currently no firm conclusions regarding the use of PEG vs NG. A large multicenter randomized control trial is currently underway which aims to address a number of key issues regarding feeding and feeding policies. These include whether early PEG or NG increases the number of patients surviving without severe disability and whether PEG or NG is associated with improved outcomes. 26
For a full description of the anatomy and physiology of normal swallowing and theories of its neural control, the reader is referred to standard texts. 15,27-29 Dysphagia has been reported in patients who have suffered cortical, subcortical, and brainstem strokes. 1-12 Our knowledge base regarding swallowing abnormality poststroke and patterns of recovery continues to evolve. 30,31 Patients with brainstem strokes generally have significant oropharyngeal dysphagia due to the location of major swallowing centers within the brainstem. In general, the more severe the swallow abnormality at 2-3 weeks postonset, the longer the swallow recovery period. 32-34 Patients with subcortical strokes may have delays in oral transit of a bolus and delayed triggering of the pharyngeal swallow. Recovery of full oral intake may take 3-6 weeks. 8 Studies have revealed differences in swallow function between patients with lesions in the left or right cerebral hemisphere. 9-11 Multiple strokes may result in significant swallow abnormality due to cumulative effects. Patients often present with a pseudobulbar palsy, have slower oral functioning with repetitive antero-posterior tongue movements preswallow and consequent decreased efficiency in oral transit, and reduced laryngeal elevation with incomplete closure of the laryngeal vestibule, all of which may lead to penetration of swallowed material. 15
Aspiration is common after stroke 5-7,35-43 and early identification is vital in planning effective management and in preventing development of aspiration pneumonia (AP). Aspiration is defined as the passage of material into the larynx below the level of the true vocal cords, and silent aspiration as the passage of material below the level of the true vocal cords in absence of cough or alteration in vocal quality. The development of AP is dependent on a number of variables including severity of stroke, conscious level, premorbid pulmonary function, ability to cough, mobility and posture, cognition, pH of aspirate, resistance to infection, oral hygiene, and frequency of aspiration. 44
In a retrospective review of 304 acute strokes, Johnson et al 35 found that AP developed within 1 year in 29 of 60 confirmed dysphagic patients. In contrast, Horner and colleagues 5 reported on a group of 47 aspirators, generally most of whom were managed with dietary modification and none of whom developed AP. Martin et al 36 found a strong association between oropharyngeal dysphagia and the diagnosis of AP, although the differential diagnosis of AP and NAP (nonaspiration pneumonia) was difficult. Schmidt et al 37 found that the odds ratio for the development of pneumonia was 7.6 times for those who aspirated compared to those who did not. Holas and colleagues 38 studied the relative risk of developing pneumonia after stroke in 114 patients and concluded that aspiration, silent aspiration, and aspiration of more than 10% of a bolus were associated with increased risk of pneumonia. Teasell et al 39 reviewed the notes of 441 stroke patients admitted consecutively to a stroke rehabilitation unit within 4 months of onset. A total of 106 patients were suspected of being at risk of aspiration. Of these, 84 were found to aspirate on thin liquids on videofluoroscopy (VFL). Only 12 of 441 developed pneumonia in hospital. The incidence of pneumonia in known aspirators was 11.9%; of the presumed nonaspirators, only 0.6% developed pneumonia. The authors concluded that pneumonia is an uncommon complication of stroke (not an observation that sits well with clinical experience). However, even from these results, aspirators are 20 times more likely to develop pneumonia than nonaspirators. Moreover, lower respiratory tract infection has been found to be more common in aspirators than nonaspirators (68% vs 6%). 40 Aspiration was closely related to the severity of the stroke.
Langmore and colleagues 41 questioned the view that there is strong link between dysphagia and development of AP. In a large study (n = 189) of elderly patients followed for 4 years, they concluded that although dysphagia is an important risk for AP, other factors (dependency on others for oral care, number of decayed teeth, presence of tube feeding, and in particular, dependency on others for feeding) emerged as more significant in development of AP. In a retrospective study of 378 consecutive stroke patients referred for VFL, Ding and Logemann 45 found that those stroke patients who developed pneumonia had a significantly higher incidence of multiple location and unspecified lesion strokes, chronic obstructive pulmonary disease, and aspiration during VFL.