Can Person With Erb's Palsy In Left Arm Build Muscles?

Can I still build muscle with erb's palsy in my left arm? I have noticed an obvious increase in muscle mass from child to adult in my left arm. My logic seems to say that signals are being sent to body telling it to build muscle there, however its still smaller, whether due to just not exercising it out of frustration, or nerve damage or both. Seeing as how there is muscle there and I have use, though limited, can I expect to see muscular development in the arm or is the muscle there just there because?