Spontaneous yawning in patients with multiple sclerosis: A polygraphic study

Patients with multiple sclerosis (MS) suffer from the repetitive yawning and sleep problems. Yawning is observed in MS and other central nervous system disorders and yawning and swallowing may be controlled by the network of the brain stem. Therefore it is important to investigate the MS patients with various clinical and radiological locations in order to understand the role of brainstem on the yawning mechanisms. One hour polygraphic recording would be crucial method for this purpose, because it is easy to observe spontaneous yawning (SY) and spontaneous swallowing (SS) together with their electrophysiologic counterparts. Previous studies reported that contagious yawn and swallow are temporally related and frequency of swallows was increased within 10s of post yawn period in normal adult subjects. We have re-investigated this phenomenon by studying the SY and SS in polygraphic recording in normal subjects and patients with MS. Then we hypothesized that SY is expected to be increased in MS patients.

49 patients with MS and 19 control subjects were recruited in this study. We used a twelve-channel electroencephalography (EEG) device. Five channels were for electromyography (EMG) recording. We also used one channel for laryngeal sensor for vertical movements of the larynx during swallowing. Cardiac rhythm, respiration and sympathetic skin responses were synchronously recorded during swallowing. We evaluated rate of total SY, swallows inside the yawning, before and after 10s of the yawning and yawning unrelated with swallowing.

Patients with MS yawned more frequently than healthy controls (p = 0,044). It was obvious that the yawning unrelated with spontaneous swallow was also significantly increased compared to normal controls (p = 0,047), whereas swallowing inside the yawn or before and after 10s of yawning were not significantly different in both groups. Among 49 MS patients, 16 (32.6%) had brainstem involvement. Yawning was observed in only 6 (37.5%) of them.

Yawning is significantly increased in MS patients compared to normal controls by using the polygraphic method. There is no direct relation of the brainstem and the origin of yawning in MS patients according to clinical picture and MRI findings. However safe swallows during yawning could suggest that there is still need to some brain stem mechanism and/or oropharyngeal reflexes. Difficulties must be emphasized to detect anatomic localization in MS because of relapsing pattern of disease.