The second finger of the left hand may have the following causes: First, tumor in the head. If there is a tumor in the head that compresses the nerve, the numbness of the second finger of the left hand can occur, and then an MRI of the head should be performed for diagnosis and, if necessary, surgery. Second, cervical spondylosis, if the nerve root is compressed by the protruding disc and hyperplastic bone in cervical spondylosis, resulting in numbness of the second finger of the left hand, cervical spine x-ray and nuclear magnetic examination should be performed for diagnosis, and cervical traction and oral nerve-nourishing drugs should be taken if necessary. Third, peripheral nerve compression, if the ulnar nerve is compressed, such as tumors around the ulnar nerve or scar adhesions of trauma, inflammatory reactions around the nerve, the numbness of the second finger of the left hand can occur.