Lesion of the Nucleus Solitarius Leads to Impaired Laryngeal Sensation in Bulbar Palsy Patients

Background In order to clarify the laryngeal sensation of bulbar palsy patients, we studied the relationship between laryngopharyngeal sensation and brainstem lesion in patients with dysphagia caused by bulbar palsy. Methods Fifteen patients with lateral medullary infarction and dysphagia were included in this study. We performed laryngeal sensory test using the flexible laryngoscope and probes method previously developed by Yaguchi et al. The test sites included the right and left tip of the laryngeal surface of the epiglottis and bilateral arytenoid regions. Lesion sites were identified by magnetic resonance imaging and classified horizontally according to Kim's classification. We also used the anatomical atlas Cytoarchitecture of the Human Brain Stem to determine whether the lesions included the nucleus solitarius and nucleus ambiguus. Results Eight cases had normal sensation and 7 cases had decreased sensation of the affected side of the epiglottis and arytenoid region. The lesions of decreased laryngeal sensation group were classified horizontally as large type or dorsal type and included the nucleus solitarius. Decreased laryngeal sensation was significantly correlated with lesions that included the nucleus solitarius (Fisher exact test; P = .026). Conclusions This study clarifies that patients with dysphagia caused by bulbar palsy may present with laryngeal sensory impairment of the affected side and laryngopharyngeal movement disorder. The important finding is that damage to both the nucleus solitarius and ambiguus cause dysphagia accompanied by decreased laryngeal sensation and that the lesions are relatively extensive and affect the middle level of the dorsal medulla.