York-led research team identifies new long-term effects of MS

Children who suffer cognitive impairment from multiple sclerosis (MS) are more likely to have less brain matter, according to a study by researchers from York University, The Hospital for Sick Children, and McGill University.

Researchers found that cognitive impairment occurs in approximately 30 per cent of children and teens with MS; reduced processing speed is most commonly observed, even early in the disease process. These deficits can impact overall efficiency of cognitive networks and disrupt learning of new information, the study says.

Christine Till “More significantly, we found the severity of cognitive dysfunction to be strongly correlated to a reduction in size in key brain regions, including the thalamus and corpus callosum, and less strongly influenced by inflammatory activity, as detected by lesion volume in the brain,” says the study’s lead author, Christine Till (right), assistant professor of psychology in the Faculty of Health at York University. “This suggests a link between cognitive impairment and the neurodegenerative component of MS, and highlights the important impact of the disease on deep grey matter structures and related neural networks,” she says.

Detailed neuropsychological evaluations and high-quality MRI scans were performed on 35 patients with pediatric onset MS who were recruited from the Pediatric Demyelinating Disease Clinic at Toronto’s Hospital for Sick Children. Researchers compared their findings to results from healthy children, who were of similar age, sex and parental education level.

MRI results showed that children with MS have overall smaller brain volumes than expected for their age. Regional analysis taking into account differences in head size showed that the thalamus, a key brain structure involved in attention, arousal, and memory, was reduced by 11.9 per cent in the MS patients. The corpus callosum, which is the largest white matter tract in the brain and important for transmitting information between brain hemispheres, was reduced by five per cent.

“A key component of MS onset during childhood relates to its effect on the developing brain,” says Till. “Overall, our findings suggest that the young age of childhood-onset MS patients does not protect them from the negative impact of the disease. We know that the earlier a patient develops MS, the greater likelihood their language development will be negatively impacted,” she says.

Approximately 24 to 40 per cent of MS patients in the study showed impaired cognitive performance on measures of processing speed and visuomotor integration (e.g. copying designs). Impairments were also noted in complex attention (e.g. simultaneously attending to multiple stimuli), visual-spatial abilities, expressive language and executive functions such as shifting attention back and forth between two stimuli, planning and organizing. In addition, the children identified with global cognitive impairment tended to be male and to have the disease for a longer duration.

“Interestingly, physical disability did not correlate with cognitive impairment, suggesting that cognitive dysfunction can be present in the absence of physical disability,” Till says.

The current research is part of a three-year study investigating the long-term effects of MS on cognitive performance. Serial analyses of MRI scans are currently underway to examine whether cognitive decline reflects the progressive neurodegenerative aspect of MS in children and teens.

“MS is increasingly diagnosed in childhood, which makes the need to understand pediatric implications of the disease all the more pressing,” says Till. “We need to fully comprehend how the disease functions in its earliest stages in order to devise interventions that can help [pediatric patients].”

The paper, “MRI Correlates of Cognitive Impairment in Childhood-Onset Multiple Sclerosis”, was published in the journal Neuropsychology in May 2011. Researchers from the Hospital for Sick Children and the Montreal Neurological Institute contributed to this study, which was supported by the MS Society of Canada.