Beijing Tiantan Hospital affiliated to Capital Medical University. Guo Er 'an, male, as of May 25th, 2023, has been the chief physician of neurosurgery in Beijing Tiantan Hospital affiliated to Capital Medical University, and a member of neurosurgery branch of China Medical College. He is good at neurosurgical diseases, such as spinal cord injury, pituitary adenoma, meningioma, brain tumor and cerebrovascular malformation.