If you have no strength in your left arm, you still need to find the cause in time. It may be due to cervical spondylosis that compresses the nerve causing the left arm to have no strength, or it may be an intracranial lesion, such as intracranial hemorrhage or occupancy that causes nerve compression, so go to the hospital for an interview with a doctor in a timely manner. If cervical spondylosis is considered, an MRI of the cervical spine can be improved. If intracranial lesions are considered, CT or MRI of the head can be improved and further treatment can be done according to the examination results. For cervical spondylosis, you can try conservative treatment first, such as traction physiotherapy. In addition, drugs that nourish the nerves, such as methylcobalamin. For severe cervical spondylosis, if conservative treatment is ineffective, minimally invasive surgical treatment, such as foraminoscopic removal of the nucleus pulposus, can be chosen to reduce the pressure on the nerve and help relieve the lack of strength in the arm.