What causes numbness in the left finger?

First of all, pay attention to whether there is carpal tunnel syndrome, or finger injury caused by factors. If the cause of injury, first need to take a film to see if there is bone damage. If regular wrist mechanical activity or fatigue is easy to cause some carpal tunnel stenosis, showing tenosynovitis problem, but also easy to cause some nerve adhesion, tendon adhesion, resulting in poor blood circulation of fingers, need to do some small needle knife treatment. There are also some traumatic factors caused by radial nerve or ulnar nerve damage, need to eat some nutritional nerve medicine symptomatic treatment. There are also vertebral artery type cervical spondylosis, usually do brachial plexus pull test positive, indicating cervical disc herniation compression nerve, nerve damage will show finger numbness symptoms.