Areas of the brain damaged by multiple sclerosis are known as lesions. In the past, disease symptoms have been attributed to the lesions that are visible on magnetic resonance images (MRIs). Recently, however, Dr. Hugo Vrenken at the Multiple Sclerosis Center at VU University Medical Center in Amsterdam, The Netherlands has found evidence that damage to normal-appearing brain tissue may actually have significant clinical impact. Disease activity in the visibly normal tissue throughout the brain may lend more to disease progression and disability than doctors had previously believed.

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