Dysphagia due to unilateral infarction within the anterior insula

Unilateral hemispheric stroke may cause dysphagia. Based on studies using functional imaging methods, the anterior insula plays an eminent role in the initiation process of swallowing. However, no unilateral lesion solely confined to the territory of the anterior insuloopercular arteries has been described as a cause of dysphagia.

A previously healthy right-handed woman was admitted with headache, dysarthria and dysphagia. Physical examination including tests of memory, intention, attention, language and related functions revealed no further neurological deficits. MRI exhibited an isolated ischemic stroke to the right insular cortex. Deglutition was evaluated by videoendoscopic examination using water, apple sauce, bread and biscuit demonstrating subsequent dysphagia. Other lesions could be excluded by MRI.

In a CT study, Daniels and Foundas reported on four patients with insular lesions. Videofluoroscopic swallowing (VFS) examination revealed „delayed swallow“ as the predominant problem. Although this study was of great value for a better understanding of the role of insular lesions in the pathophysiology of dysphagia after brain injury, there are three points which have to be critically discussed. Firstly, CT scanning has a much worse spatial resolution. Secondly, in the patients with dysphagia the lesion was not confined to the insula: In patient 1, the infarction extended from the right anterior insula via the subinsular white matter and the claustrum into the basal ganglia; patient 2 with infarction of the right anterior and posterior insula had also a significant lesion of the frontoparietal and temporal operculum and suffered, therefore, from a contralateral hemiparesis; in patient 3 the infarction of the left anterior insula comprised also the basal ganglia as well as parts of the frontoparietal and temporal operculum. Thirdly, with respect to pure insular lesions a percentage of over 10% (4/39) would have been unusually high.

Summarizing, the anterior insula and the adjacent medial surface of the frontal operculum seem to be a critical region with regard to swallowing disturbances in the case of a circumscribed lesion confined to this area.