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Dysphagia characterized by aspiration subsequent to pontine stroke.

Article Excerpt
It has been reported that a pontine lesion often results in dysphagia characterized by aspiration. However, the patterns and characteristics of such dysphagia are unknown. We studied 57 patients (34 men, 23 women) with possible dysphagia consequent to pontine stroke. We compared the aspiration characteristics with three different pontine lesion loci (e.g., unilateral, bilateral, and pontine-plus group). Fifteen of 57 patients (26.3%) aspirated upon a spoonful quantity of barium. All 15 aspirators had either a bilateral pontine or pontine-plus lesion. Nine of the 15 (60%) aspirators were "silent" aspirators as revealed in the VFS studies. The conclusion to be drawn from this study is that, unlike the widespread belief, aspiration symptom due to an isolated unilateral pontine infarction may be uncommon and transient.

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Dysphagia may be manifested in several forms. Among them is aspiration defined as the tracheal invasion of foreign material or saliva below the true vocal folds (Logemann, 1998). Aspiration itself can be seriously detrimental to stroke patients due to its apparent sequela, aspiration pneumonia. Its risk may further rise with "silent" aspiration upon which a patient may not be conscious of the tracheal invasion and thus fails to manifest protective reactions such as coughing, throat clearing, and the like. Thus, silent aspiration can only be detected by an instrumental tool such as videofluoroscopic swallowing (VFS) study or fiberoptic endoscopic examination of swallowing evaluation.

Dysphagia is a common consequence of stroke in the brain stem, including medulla oblongata and pons (Caplan & Han, 1995; Horner et al., 1991; Kim et al., 2000). It has been well known that a swallowing center is situated in the medulla oblongata (Jean, 1984; Jean, Car, & Roman, 1975) and consequently its lesion can be unfavorable to normal swallowing functions. Further, pons as a connected swallowing pathway with medulla is also an important structure for swallowing function in a coherent manner (Kessler & Jean, 1985). It is common to observe dysphagia as a clinical finding of a large bilateral infarct and a pontine hemorrhage (Horner et al., 1991). In a clinical situation, however, patients with even a relatively small pontine lesion also may report swallowing difficulties manifested as intermittent invasion of food into the airway resulting in throat clearing or coughing. In this regard, a guideline in the decision-making process is necessary because a clinician needs to pursue an immediate, alternative feeding mode such as a nasogastric (NG) tube.

To our knowledge, dysphagia due to pontine lesions has received relatively little attention. Although Horner et al. (1991) investigated 23 subjects with brain stem stroke, the patient group was rather heterogeneous in terms of the nature of the lesion. Of their 23 subjects, there were only 5 patients with pontine-focused lesions and 8 with concomitant cerebellar lesions. The remainder had brain stem lesions elsewhere such as in the medulla oblongata or midbrain.

The underlying neurophysiological causes of aspiration are multifaceted, given that both reduced functions in the oral mechanism, and pharyngo-laryngeal abnormalities also may result in tracheal invasion by foreign material under the vocal folds. Thus, it may be of interest to investigate the extent of a neurological lesion that relates to the dysfunction of oral and pharyngo-laryngeal swallowing mechanisms associated with aspiration by pontine stroke patients.

This study aimed to investigate the relationship between the extent of a pontine lesion and aspiration. Improved understanding of the association will increase the knowledge of neuropathophysiology as it concerns poststroke outcomes, thereby facilitating more efficient use of health resources for this patient group.

PATIENTS AND METHODS

Subjects

One hundred-seventeen consecutive patients with pontine stroke and consequent dysphagia were referred over a 6-year period to the Speech & Swallowing Clinic of the Department of Neurology at a tertiary-care university medical center. The inclusion criteria of patients were to include those with (a) stroke at pontine area; (b) recent MRI results; (c) no previous strokes in other brain areas than pons; and (d) no other concomitant neurological diseases. Of the 117 patients, therefore, the following 60 patients were excluded from the patient-pool, reducing the number of subjects into 57 patients:

1. 4 patients with extensive time-gap between radiographical studies and the VFS studies;

2. 22 without radiographical results;

3. 31 with previous stroke episodes;

4. 1 diagnosed with Guillain-Barre syndrome six years before the left pontine infarction;

5. 1 with 7 years of epilepsy history; and

6. 1 with a tracheostomy tube.

The tracheostomy tube has been reported to exert a negative effect on swallowing (Eibling & Gross, 1996). In the 57-patient pool, we included 9 patients with new pontine lesions in addition to previous history of stroke in the pons. As shown in Table 1, the subject group consists of 34 men and 23 women of ages ranging from 42 to 92 years (Mean: 67.2; SD: 9.7).

Data Collection and Analysis

Neurological Lesion and Neurofunction...