Fill the blank space to complete the text.
A 60-year-old woman, after a viral infection, for about two months with prolonged walking gets tired faster. Over time this complaint has progressed, and has recently added difficulty swallowing. It is difficult for eater to swallow water. Her voice changed – became a nose. Lately her head has been tingling in the afternoon due to weakness for neck muscles. From the neurological status a pathological syndrome is established, muscle fatigue with mild ptosis, bilateral dysphonia, dysphagia, rhinolalia. Count to 10 takes 10 steps then gets tired and short of breath. Electromyography has data for decrement 59% what is the most likely clinical diagnosis?