Biogen Idec and Elan's recalled multiple sclerosis (MS) drug Tysabri has been approved by European regulators for patients with the severest cases of the disease.

The European Commission announced that the drug can also be used by those who haven't been helped by older treatments, the companies said.

The medicine was pulled from the market more than a year ago due to the risk of a rare brain infection. Biogen Idec and Ireland-based Elan are currently working with regulators on a program to manage the risks associated with the drug, the companies said.