Brenda L. Banwell, MD, is Chief of the Division of Neurology at Children’s Hospital of Philadelphia and holder of the Grace R. Loeb Endowed Chair in Neurosciences. Dr. Banwell is an expert in pediatric-onset multiple sclerosis (MS) with a clinical focus on cognitive features, neuroimaging, T and B-cell autoimmunity studies, and studies of viral triggers. We spoke with Dr. Banwell to discuss the disease course of pediatric-onset MS and the impact of magnetic resonance imaging (MRI).
How does the disease course of pediatric-onset MS differ from that of adult-onset MS?
DR. BANWELL: Pediatric-onset MS is almost universally a relapsing-remitting disease at onset. Primary progressive MS is typically not seen in children younger than 18 years of age.
Children with progressive disability from onset should be considered more likely to have either a mitochondrial disease, genetic leukodystrophy or other disorder. Multiple sclerosis would not be a consideration for a child with progressive disability at the beginning.
Secondary progressive MS does not appear to occur for most children during the first 10 years of disease. Retrospective cohort studies suggest that secondary progressive MS in patients with pediatric-onset MS likely takes, on average, at least 20 years to occur from onset.
However, we should remember that pediatric-onset MS patients are at risk for secondary progression when they are only 30 or 35 years of age, depending on when they experienced their first attack. With the availability of numerous MS therapies, we are optimistic that secondary progressive MS may now be less likely to occur, or may be delayed even further from onset.
How often are MRIs performed on children with MS?
DR. BANWELL: The most pivotal MRI is the one that helps you confirm the diagnosis. It is ideally obtained very close to the first onset of symptoms. That MRI could include the orbits, brain, and spine, depending on the clinical symptoms.
Following the first MRI scan, most of us would image our patients approximately every 3 months in the first year. After the first year, we would typically image our patients at least every 6 months, until, if they have been stable for an extended period of time, we might move to annual imaging.
The frequency of MRI scanning is determined by clinical disease activity, treatment decisions, and the age of the child. For example, very young children may require repeated exposure to anesthetics in order to obtain an MRI. We might have to think strategically about how often to put them under that degree of anesthesia to obtain imaging. Many young children are able to lie still for MRI if the facility has the option for viewing a video during the scan.
How do those MRI results influence your treatment decisions for the pediatric patient?
DR. BANWELL: The International Pediatric Multiple Sclerosis Study Group recently had an international consensus discussion with respect to monitoring disease activity and are working as a collective toward the concept of defining a standard interpretation of adequate disease control for given treatments. Standardized protocols for clinical evaluations and for MRI scan interpretation will be essential. Determining what constitutes “adequate treatment response”, both in terms of relapse frequency and frequency of new lesions on MRI will be important components to consider.
What have the MRI studies shown us about the brain volume in pediatric patients with MS?
DR. BANWELL: There are several things that we have learned about the impact of MS in the brains of children and teenagers.
With respect to brain growth and brain volume, we have learned that at the time of a first attack, children and teenagers with MS already have brain volumes that are about one standard deviation below what you would expect for someone their age and sex.
The inner skull size is also reduced, which suggests that there has been a failure of head and skull growth even before the first attack.
Following identification of MS in a child, the subsequent serial MRI studies have shown that children with MS fail to have age-expected brain growth. We do not see the age-expected rate of growth in our pediatric patients.
Around age 16 to 17 is when our brain volumes are the largest in our lifetime, but our pediatric patients show brain atrophy or progressive loss of brain volume after age 15, a time when normal brain volumes are pretty stable for at least a decade.
When we age, there is a gradual rate of brain volume loss, but this has not been imaged yet in our pediatric patients with MS since we do not have serial studies of individuals who are 30 or 40 yet who had pediatric-onset MS.
What else have MRI studies shown?
DR. BANWELL: Another point to add is that when we look at patients with pediatric-onset MS compared with those with adult-onset MS matched for disease duration, pediatric patients on average have higher T2 and T1 lesion volumes compared with adults. This suggests that despite their young age, pediatric-onset MS patients have had sufficient time to accrue subclinical disease/lesions and may have an accelerated rate of new lesion formation.
MRI and some of the newer more advanced MRI techniques are also informing on brain tissue integrity. In studies that examine whether the white matter highways in the brain or the pathways in the brain are normal, we find that in both pediatric-onset and adult-onset MS, even normal-appearing white matter is not normal. It is not as well structured as it should be compared with age- and sex-matched controls. Further, the myelin integrity or the structural alignment in the brain of our pediatric patients may not be normal.
I think that emphasizes to all of us that MS is much more than just multiple areas of “sclerosis” or scarring, which is what MS actually means. It is indeed a disease that has a more widespread impact on the central nervous system, beyond the very bright T2 lesions that we normally count and measure.
That is important because it speaks to the subsequent requirement that we think about when considering treatment for MS. Our goal is to not only suppress the acquisition of new lesions, which is the common metric for clinical trials, but we also think about brain protection, brain preservation, and brain repair, which, I think, is potentially the underlying substrate that is not yet fully addressed by the evolving treatment.