Electrophysiological Evaluation of Dysphagia in the Mild or Moderate Patients with Multiple Sclerosis: A Concept of Subclinical Dysphagia.

Swallowing mechanism and neurogenic dysphagia in MS have been rarely studied by electromyographical (EMG) methods. This study aims to evaluate the presence of subclinical dysphagia in patients with mild multiple sclerosis (MS) using electrophysiological methods. A prospective study of 51 patients with relapsing remitting multiple sclerosis and 18 age-matched healthy adults was investigated. We used electromyography to measure the activity of the submental muscles during swallowing. Electrophysiological recordings of patients were obtained during relapse, after relapse, and at any time in remission period. Clinical dysphagia was found in 12% of MS patients, while electrophysiological swallowing abnormalities were encountered in 33% of patients. Subclinical dysphagia was determined in 35% of patients during an MS relapse, in 20% of patients after a relapse, and in 25% of all 51 patients in the remission period based on EMG findings. Duration of swallowing signal of submental muscles in all MS patients was found to be longer than in normal subjects (p = 0.001). During swallowing of 50 ml of sequential water, the compensatory respiratory cycles occurred more often in MS patients than normal subjects, especially during a relapse (p = 0.005). This is the first study investigating swallowing abnormalities and subclinical dysphagia from the electrophysiological aspect in MS patients with mild disability. The electrophysiological tests described in this study are useful to uncover subclinical dysphagia since they have the advantage of being rapid, easy to apply, non-invasive, and without risk for the patients.