Dysphagia is a condition characterized by difficulty swallowing. There are many potential causes of dysphagia, including neurological disorders (such as stroke or Parkinson's disease), structural abnormalities (such as a stricture or tumor), muscular disorders (such as myasthenia gravis or muscular dystrophy), and various systemic diseases (such as scleroderma or sarcoidosis). In some cases, the cause of dysphagia is unknown.