The woman who underwent brain surgery over the weekend after plunging down a flight of subway stairs during an attempted mugging of her and her son is still unconscious — and doctors fear she may never wake up, her heartbroken family said. The grim update on 58-year-old Than Htwe’s condition, which was announced Tuesday by her family, came as police are still searching for the brute who left her on the brink of death. “The doctors told us that the trauma to her head was so severe that she won’t be able to wake up,” the son, Kyaw Zaw Hein, and her husband, Myint Shein, said on a newly created GoFundMe page. “Eventually all her organs will shut down. We are now just waiting and worrying about what happens next,” the family said. Hein, 22, was with his mother on their way to her doctor’s office when they were attacked from behind in the Q train station at Broadway and Canal Street at about 9:40 a.m. Saturday, according to police. The two were walking up the stairs at the station when the attacker grabbed Hein’s bookbag, causing him to fall backward, authorities said. As Hein fell down the stairs, he reached for his mother, who plunged down the steps with him, police said. Htwe’s head struck the ground and she was left bloodied as the suspect fled back into the subway station. A witness to the senseless attack had told The Post Hein consoled his badly injured mom as he pleaded for assistance. “I saw the [son] holding the lady’s hand and he was screaming for help,” Carlos Lopez, a coffee-stand worker, recalled. “There was a lot of blood coming out of her head,” said Lopez, who flagged down nearby officers.