 U.S. President Joe Biden has not undergone any special neurological testing since his annual physical in February, according to his doctor. The statement comes after questions from reporters about White House visitor logs showing a neurologist visited eight times over the past year. Doubts over the U.S. president's future are threatening to overshadow the NATO summit that begins today in Washington. Joe Biden's hosting the gathering, but other leaders, including Emmanuel Macron and Olaf Scholz, are facing pressure after recent elections in their countries.