As of this writing even his doctors are having difficulty diagnosing what could be causing Bryan discomfort at this point. However, Bryan's health has been a problem that everyone has been talking about since his return late last year and some people who didn't want to admit the possibility were even talking about it.
Many people believe that Bryan's health being a question is the main reason why he wasn't thrust right back into the World title picture when he came back like many thought he should have been. Whether you want to admit or not if Bryan isn't/wasn't 100% their is No reason why WWE should give him the World Title. Even if you believe he is the best worker in the company right now it would be stupid to invest so much in someone who could just back on the shelf for a long time again. Fans need to relax and give Daniel time to prove he can stay healthy and then when he proves that he can stay healthy he will be back in the World Title picture. Because in every sense of the word the wrestlers health comes first before anything else as without there would be no wrestler.
As was announced on Raw, Daniel was sent home from the UK due to possibly suffering a concussion on tour and management wanting him to rest. But now Daniel's title defense this Sunday could be in question if he is not 100%. All I can say is send Daniel your well wishes and your hope that he makes to Extreme Rules and can remain injury free. Because having a talent that can add life to a crowd just by doing one action is an invaluable asset to the WWE and would tremendously hurt the company if they were to lose him again.