[The correlation between dysphagia and involvement of the ambiguous nucleus on MRI in acute-phase lateral medullary syndrome].

In this study, the clinical features and MRI findings of 21 patients admitted for acute lateral medullary syndrome, including 10 patients with dysphagia, were examined. According to Cytoarchitecture of the Human Brain Stem (Olszewski, J & Baxter, D), MRI-identified lesions were classified into four groups based on their location (upper, middle-upper, middle-lower, and lower parts of the medulla oblongata). We also examined whether each lesion involved the ambiguous nucleus (AN). We then studied the correlation between dysphagia and involvement of the AN. Ten patients had dysphagia, which improved very quickly in all but one. In the horizontal plane, lesions of all patients with dysphagia exhibited AN involvement, suggesting that dysphagia is strongly correlated with AN involvement. Among the 8 patients with lesions in the upper part of the medulla oblongata, the lesions of 7 patients included the AN, and 6 of those 7 patients had dysphagia. Among the 5 patients with lesions in the middle-upper part of the medulla oblongata, the lesions of two contained the AN, and one of those two patients had dysphagia. Among the 6 patients with lesions in the middle-lower part of the medulla oblongata, all lesions contained the AN, but only 3 of the patients exhibited dysphagia. In both patients who had lesions in the lower part of the medulla oblongata, the lesions did not include the AN and neither patient had dysphagia. Patients who had lesions involving the AN in the rostral part of the medulla oblongata were more likely to have dysphagia than the other patients. On the other hand, half of the patients with lesions involving the AN in the middle-lower part of the medulla oblongata did not have dysphagia. This might suggest that the caudal part of the AN has little involvement in the mechanisms of dysphagia.