January 7, 2010

One question about MS that really interests me is why severity of symptoms can vary so widely among people with the same diagnosis. It seems that if this was better understood, perhaps the knowledge about the less-severe forms could be turned into therapies, or at least people diagnosed with MS could get a better sense of what may lie ahead for them. Here are a couple of recent studies from research teams looking into this topic.

The first study comes from a group of Italian researchers who looked carefully at MRIs from people with benign MS (EDSS <=3 with disease duration >= 10 years) for clues as to why their motor function was relatively unimpaired. These subjects were first screened for cognitive function to rule out significant problems which would contradict the determination of "benign MS." By analyzing MRI measurements in motor-related brain regions and the spinal cord, and comparing them against those from healthy controls, the researchers found something interesting. In the people with benign MS, there was evidence of gray matter volume loss in the brain and extensive demyelination in the spinal cord. However, a measurement called fractional anisotropy (FA) that reflects the integrity of the axonal pathways in the spinal cord was the same in the MS group compared with the controls. Whether the disease mechanisms at work in MS tend to spare spinal cord axons in benign MS, or whether these results are due to strong axonal repair/plasticity mechanisms in people with benign MS, still remains to be seen.

The second study looked at why intellectual enrichment appears to protect against cognitive decline in MS and other neurological diseases. This study was carried out at UMDNJ-New Jersey Medical School where 18 people with MS were recruited. Each person was assessed for vocabulary knowledge as a measure of educational attainment, and each was given MRIs, including functional MRIs showing which brain areas were active while the subjects performed cognitive tests.

Having greater educational enrichment didn't result in less brain atrophy or better performance on simple cognitive tests. However, greater enrichment was associated with better scores on more complicated tests. Furthermore, enrichment level appeared to affect the types of brain networks that were used while performing these cognitive tests. MS subjects with higher intellectual enrichment were able to use their "default network" (brain areas active during rest) during the cognitive tests more than those with lower enrichment, who had to recruit other brain areas more heavily while performing the tests. This shift away from the default network has been seen in other neurological conditions as well as in aging, and is thought to represent cerebral inefficiency. The authors interpret these results to mean that greater intellectual enrichment doesn't provide complete protection against brain atrophy and cognitive decline, but does give people with MS more of a buffer before cognitive effects become apparent. Also, exactly how intellectual enrichment connects with cerebral efficiency is not yet known, but if it turns out that there's a direct effect, perhaps cognitive training of people with MS can help build up this buffer as well.