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.