BBC News
A controversial new treatment for alzheimer's has been approved in the us by the us food and drug administration. it's the first treatment approved for the disease after nearly two decades of failed efforts and is the first that attacks the disease process rather than just easing symptoms. aducanumab targets the underlying cause of alzheimer's, the most common form of dementia. patient groups have campaigned for its approval, but some experts have advised against its approval. our health correspondent katharine da costa is with me. this is significant, explain why. it really is a major milesto...