Hi,thank you for posting your query on health care magic. Difficulty in swallowing might be due to causes like Enlarged base of tongue,retroverted epiglottis, Gastroesophageal reflux,Spam of upper esophageal sphincter (Cricopharynx), esophageal motility disorders, Stricture or any growth in esophageal. You have already undergone MRI brain ,CT scan neck,Test for Myasthenia gravis and Multiple Sclerosis. I would advise you to consult an Otolaryngologist doctor for examination of your throat and larynx to rule out any obstructing lesion. Also advise you to consult a Gastroenterologist doctor to have Upper Gastrointestinal endoscopy. If esophageal motility disorders are suspected,then Esophageal manometry test might be needed. In case of Gastroesophageal reflux,you may need to take proton pump inhibitors like pantoprazole. In case of Cricopharynx spam,stress and anxiety is the main cause.Stress reduction and muscle relaxant will usually alleviate your symptoms. Hope this answers your question.Take care.