To evaluate masticatory performance, the study method proposed by Kazunori et al. [5] was used with some modifications. After asking the subjects to chew a 2.5 cm×1.5 cm×1.0 cm sized commercialized soft candy 30 times and spit it out, the gathered candy fragments were rinsed with flowing water to remove saliva. The candy fragments were put into 20 mL of distilled water and stirred for two minutes with a tongue depressor. The supernatant liquid was collected and the concentration of dissolved glucose was measured with a blood sugar meter. To eliminate the effects of temperature and humidity, the concentrations before and after mastication were compared at the time of every test to measure increment in the surface area of masticated candies. The subjects were divided into three groups: a group in which the surface area increased by 0%-25%, a group in which the surface area increased by 25%-50%, and a group in which the surface area increased by 50% or more.

To evaluate sensation of oral cavity, the two point discrimination test proposed by Guilleminault et al. [6] was used with modifications. The two point discrimination test is a composite sensory test used to measure when the distance before two points is felt as one point when two points are stimulated simultaneously. The method is to measure a distance at which the subjects could easily distinguish two points first and then gradually decrease the distance. Needles with non-sharp ends were fixed to pincers and the distances at the left/right side walls of the palate and the basal region of the uvula in random order were measured. The distances were measured in a unit of 1 mm and the measurement was conducted two times at each site, six times in total. There were interval distance of at least 2 mm at each session and the subject took a rest for two minutes after each session. The averages were obtained and the subjects were divided into three groups: a group of shorter than 10 mm, a group from 10 to shorter than 15 mm, and a group of longer than 15 mm.

History taking, NIHSS and evaluation of masticatory performance and sensation of oral cavity were conducted by one researcher before the VFSS was conducted.

VFSSs were conducted on the same day at the same place [7]. The aforementioned studies have high inter and intra test reliability. To avoid errors in the results of the VFSS due to nasogastric tubes, nasogastric tubes were removed from all the patients 20 minutes before the studies, and after removing secretions in the oral cavity and decompressing balloons in tracheostomy patients. One specialist in dysphagia in the rehabilitation medicine department implemented modified Logeman's protocol [8]. The protocol was implemented after conducting the fluoroscopy when the patient was sitting laterally at the fluoroscope so that accurate anatomical structures were shown and while video-recording the fluoroscopic screens. In each study, dysphagia diet I, a mixture of 80 g of yogurt and 10 g of water-soluble barium, was used and the study began with the doctor's instruction, "Swallow it" after putting 30 g of the diet at a time into the mouth of the patient using a spoon. The study was conducted one time when the patient was wearing dentures. The dentures were removed, any test medium remaining in the pharyngolarynx was removed using coughing and double swallowing, any test medium remaining in the oral cavity was spit out and the oral cavity was rinsed using normal saline. The same process was repeated after a resting time of five minutes. After the study, the video was played, motions were captured and 2D quantitative analyses were conducted using Adobe Photoshop CS3 (Adobe Systems Inc., San Jose, CA, USA) by the Department of Electrical Engineering, University of Ulsan. The produced data were read by a physiatrist. To avoid decreases in measured values due to masking caused by the radiopacity of dentures, the maximum area of the test diet gathered on the tongue when the mouth was open before swallowing began was measured and the maximum area of the test diet in the oral cavity when the mouth was open after swallowing was completed was measured. The definitions of the measured variables are as follows. Oral cavity transit time (OTT) is the time (second) from the moment at which the major bolus in the oral cavity began to move posterior to the moment at which the front end of the bolus arrived at the point of crossing between the lower edge of mandibular ramus and the tongue base, pharyngeal transit time (PTT) is the time (second) from the moment at which the front end of the bolus arrived at the point of crossing between the lower edge of mandibular ramus and the tongue base to the moment at which the rear end of the bolus passed the cricopharyngeus, oral cavity residue is the percentage of bolus remaining in the oral cavity, pharyngeal residue is the percentage of bolus remaining in the pharynx, oropharyngeal swallow efficiency (OPSE) is the value obtained by dividing the fraction of bolus swallowed through the esophagus by the total time taken to pass the oropharynx and aspiration is the passing through the vocal fold of foods [9].