What Causes Numbness In Pectoral And Bicep Region?

Hi I am a 45 yr old male and having numbness in my upper left pectoral area that is trailing across the front of my shoulder into upper bicep region. I had shingles in left bicep and back of shoulder 2 yrs ago . Wondering generally about causes of numbness in this area and also whether this could be some residual effectsof the shingles affecting a nearby area, etc... thank you