Aside from pressure on a nerve, there are many possible causes of numbness in the face or leg such as nerve injury, medication side effect, pressure on peripheral nerves from enlarged blood vessels, tumors, scar tissue, or infection, lack of blood supply to an area and medical conditions such as diabetes, migraines, transient ischemic attack (TIA), stroke, underactive thyroid, vitamin deficiency and abnormal levels of calcium, potassium, or sodium in your body.