In 2010, Robert F. Kennedy Jr. was experiencing memory loss and mental fogginess so severe that a friend grew concerned he might have a brain tumor. Kennedy said he consulted several of the country’s top neurologists, many of whom had either treated or spoken to his uncle, Sen. Edward Kennedy, before his death the previous year of brain cancer. Several doctors noticed a dark spot on the younger Kennedy’s brain scans and concluded that he had a tumor, he said in a 2012 deposition reviewed by The