Although the sequence of events involved in swallowing varies among healthy adults, healthy adults demonstrate some consistent patterns, including opening of the upper esophageal sphincter (UES) prior to maximum laryngeal elevation (LE). Previous animal studies suggested that swallowing is regulated by a neuronal network in the medulla, and lateral medullary infarction, or Wallenberg syndrome, frequently causes dysphagia. This retrospective, observational, multicenter study aimed to determine if the sequence of swallowing events was disturbed in patients with Wallenberg syndrome compared with previously published reference data for healthy adults. The study subjects included 35 patients with Wallenberg syndrome admitted to three hospitals in Japan from 1/4/2009 to 31/3/2017. Sixteen timing events, including maximum LE and UES opening, and the intervals between events were measured. If the sequence of events was the same as in healthy adults, the interval value was positive, and if the sequence of events was opposite to that in healthy adults, the value was negative. The median interval from UES opening to maximum LE was − 0.02 s (range − 0.80 to 0.89, 95% CI − 0.14 to 0.10). About half of the Wallenberg cases showed negative values indicating that the sequence was reversed. These results suggest that lateral medullary infarction impairs the sequence of swallowing events.
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The authors would like to thank Prof. Masako Kurachi for advice on defining timing-related events, and Prof. Yoshimi Suzukamo for advice on methods related to statistical analysis. Part of this work was presented as a poster at the 2018 Dysphagia Research Society Conference (DRS), Baltimore, USA. We also thank Prof. Catriona M. Steele and Susan Furness, PhD, from Edanz Group (www.edanzediting.com/ac) for editing a draft of this manuscript.
Compliance with Ethical Standards
Conflict of interest
Mari Nakao declares that she has no conflict of interest. Fumiko Oshima declares that she has no conflict of interest. Yutaka Maeno declares that he has no conflict of interest. Shinichi Izumi declares that he has no conflict of interest.
This study was approved by the Institutional Review Board of Tohoku University School of Medicine (ID 2016-1-857) with the 1964 Helsinki Declaration and its later amendments. This article does not contain any studies with human participants, materials acquired from human body parts, or animals performed by any of the authors. Information including ethical standards and contact information on this study was disclosed on the web site of each facility that participated in this study.
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