My friend had a picc line in his left arm to drip antibiotics onto his heart. It has been 7 years since he had it and now he is experiencing numbness in this arm and its been about 2 to 3 weeks. Could this be related to the picc line? What other reasons would he be having numbness in his arm?
Probably not. There are many reasons for numbness in the arm most commonly entrapment of the nerves at the elbow or wrist from repetitive motion such as typing on a keyboard or lifting things for a job.  Also pinched nerves in the neck can do, but usually this is associated with pain first.  A neurologist could sort it out for him.  The treatment depends on the cause