The FDA’s conditional approval of Biogen (NSDQ:BIIB) and Eisai’s (OTCMKTS:ESALY) Alzheimer’s drug aducanumab (Aduhelm) may have been controversial, but the decision will likely have a significant financial impact. There are 6 million people with Alzheimer’s in the U.S. alone, according to Alzheimer’s Association estimates. Approximately half of those patients have mild symptoms, which is the group most likely…