Of the available disease-modifying treatments for multiple sclerosis, Tysabri (natalizumab) has arguably been the most controversial to date. The reason for this controversy is a condition called progressive multifocal leukoencephalopathy or PML. Any patient who is trying to decide whether Tysabri is the right medication for personal use, she/he must balance the risks and benefits and how those might fit into his lifestyle or circumstances.
Of the 79 Tysabri patients who developed PML,...

