How is the oropharyngeal phase of swallowing clinically evaluated?

See this video clip http://www.nature.com/gimo/contents/pt1/images/gimo19-v3.mov

It is a videofluoroscopic study of the oropharyngeal phase of swallowing that shows aspiration of barium sulfate into the trachea. Patients with strokes affecting the medulla, myasthenia gravis, or motor neuron disease may have defects in swallowing that increase the likelihood of aspiration pneumonia.