Silent Laryngopharyngeal Sensory Deficits After Stroke
Dysphagia and aspiration are two devastating sequelae of stroke. Recent work has shown that laryngopharyngeal (LP) sensory deficits are associated with aspiration in stroke patients with dysphagia. The phenomenon of silent LP sensory deficits, where the patient exhibits no subjective or objective evidence of dysphagia, yet has an LP sensory deficit, has not been previously described. The aim of this study was to evaluate the sensory capacity of the laryngopharynx in stroke patients who had no subjective or objective complaints of dysphagia. We determined the sensory threshold in the laryngopharynx using air pulse stimulation of the mucosa of the pyriform sinus and aryepiglottic fold. Eighteen stroke patients (mean age 65.6 ± 11.5 years) and 18 age-matched controls were prospectively evaluated. Normal thresholds were defined as <4.0 mm Hg air pulse pressure (APP). Deficits were defined as either a moderate impairment in sensory discrimination thresholds (4.0 to 6.0 mm Hg APP) or a severe sensory impairment (>6.0 mm Hg APP). Stroke patients were followed up for 1 year to determine the incidence of aspiration pneumonia (AP) as verified by chest radiography. In 11 of the stroke patients studied, either unilateral (n = 6) or bilateral (n = 5) severe sensory deficits were identified. The elevations in sensory discrimination thresholds were significantly greater than those in age-matched controls (7.1 ± 0.6 mm Hg APP versus 2.5 mm Hg APP; p < .01, Wilcoxon score). Among patients with unilateral deficits, sensory thresholds were severely elevated in all cases on the affected side compared with the unaffected side (p < .01, Wilcoxon score). Moreover, the sensory thresholds of the unaffected side were not significantly different from those of age-matched controls. Aspiration pneumonia did not occur in the patients with normal LP sensation or in the patients with unilateral severe LP sensory deficits. However, in the 5 patients with bilateral, severe LP sensory deficits, 2 developed AP, both within 3 months of their LP sensory test. The results of this study showed, for the first time, that stroke patients without subjective or objective clinical evidence of dysphagia could have silent LP sensory deficits. These impairments could contribute to the development of AP following stroke. The findings in this study suggest that LP sensory discrimination threshold testing should not be restricted only to patients with clinical dysphagia.