If the symptoms of numbness in the left arm appear, if the neck feels uncomfortable, and if the time spent with the head down is too long, it may be related to cervical spine disease, so you can do more neck massage, hot compresses, activities, and if necessary, traction and acupuncture treatment. 2. If nerve damage is caused by trauma, numbness can be treated by intramuscular injection of vitamin B1 and vitamin B12. Numbness in the left arm, if accompanied by dizziness, headache, numbness in the lower limbs, restricted movement and other symptoms, may be related to cerebral thrombosis, cerebral infarction, etc., and can be treated with Ginkgo biloba injection or thromboxane infusion.