Dr. Apatoff, what do we mean when we say "cognitive impairment"?
BRIAN APATOFF, MD: Cognitive impairment is really a very general term to describe some subtle -- and sometimes not-so-subtle -- changes in higher cortical functioning, intellectual functioning that most of us take for granted in our day-to-day activities -- things like memory, things like terms that describe executive function, our ability to take care of five different things at one time. These are controlled by the complex integration of different regions of the brain, and if you have multifocal brain injury, as can occur in multiple sclerosis, you can have some impairment of these cognitive functions.
DAVID FOLK THOMAS: Dr. Phillips, explain how somebody with MS might be cognitively impaired. What effect MS has on that.
TED PHILLIPS, MD: As Brian mentioned, sometimes it can be of a very subtle nature and actually require specialized neuropsychological testing to be able to detect it. But a patient with MS reporting those kinds of problems might say something like they're having difficulty concentrating on the work at hand or keeping track of more than one thing. Although one has to be careful to distinguish between cognitive impairment that might be MS-related versus a particularly or overly stressful life or even, as you mentioned earlier, the possibility of co-existing depression.
DAVID FOLK THOMAS: Dr. Galetta, how many MS patients, what percentage suffer cognitive impairment?