AAN 2022 | Defining spinal cord reserve and its correlation with disability in MS

The concept of spinal cord reserve runs in parallel to the concept of brain reserve. This concept hasn’t been described before, but it makes all sense with regards to the general concept of reserve. So in brain reserve, what you are using is the total intracranial volume as a proxy of maximum lifetime brain growth. In the spinal cord, what we could use as a proxy, is the area of the spinal canal as a proxy of maximum lifetime growth of the spinal cord. In brain reserve, the larger your brain, the larger your resilience, the larger your resistance to brain damage caused by a disease. This was described in Alzheimer’s, but has been confirmed in multiple sclerosis. Spinal cord, the concept will be the same, the larger your spinal core canal, the larger your resilience, your resistance to damage caused by the disease.

In particular, in multiple sclerosis, the damage caused by the disease tends to focus very much on the spinal cord and this damage is very, very clinically relevant. So it makes a lot of sense to look at that. We have interrogated a sample of more than 3000 MRI. We use brain acquisition but covering the spinal cord. And using appropriate statistical tools, we have shown that the larger your spinal canal, the lower your disability levels adjusting by other relevant factors like sex, age and also brain and a spinal cord damage caused by the disease.

There are logical next steps, which we are already moving forward at the moment. First is, ours was a cross-sectional study, so we need to prove this in a longitudinal sample, this is first. Second, as I mentioned before, we have used brain acquisitions, which we know by previous research that can be used to obtain spinal cord parameters, but it would be better if we use spinal cord acquisitions, so this makes us a lot of sense. And finally, the disability outcome measure that we use in our present study, is a patient-reported disability score, the so-called PDDS, patient-determined disease steps. We should prove this using EDSS, so let’s say, gold standard measure of disability, multiple sclerosis.

Their immediate implications in clinical practice, I would say are not there, but they very nicely close the circle of reserve, because you have brain reserve and you have cognitive reserve, which is a functional type of reserve. Then you have physical reserve, which is a functional type of reserve, but related to physical enrichment in your previous premorbid life. But now we have the counterpart of mostly physical functional reserve, which is the structural spinal cord reserve. So with this, we close this circle, we give full sense to the models and we can say confidently to people that, “Okay, we have a structural reserve that is fixed, but that we should take into account when modeling as prognostic factor.” And on the other hand, we could reinforce our message of keeping a very healthy lifestyle premorbidly and during the disease by enriching you continuously on a cognitive level and also at a physical level.