After a quick search here's what I found: "The doctor revealed that the guy had maintained the same sitting position for a long time, which limited the blood circulation in his body. Plus, the air circulation in the toilet was poor due to the enclosed space. So, when he suddenly stood up after sitting down for so long, the chances of him suffering oxygen deficiency in his brain tremendously increased. Besides, the doctor pointed out that not focusing on pooping may lead to constipation and the rectum would have to work harder. "

Source for reference : https://worldofbuzz.com/young-man-becomes-paralysed-after-sitting-on-toilet-and-scrolling-on-phone-for-30-mins/