While MRI is very sensitive when it comes to detecting abnormalities, it is not very specific as to their aetiology. Patients can be erroneously labelled with the diagnosis of MS when detecting small white matter abnormalities in the form of hyperintensities, which should not, however, be confused with MS lesions. These abnormalities may be due to micro-ischaemic disorders, may be congenital in origin, occur in people with migraine, diabetes or hypertension, etc. 

By contrast, typical MS lesions are sometimes detected in people who undergo an MRI of the brain for a completely different reason, for example due to major headaches or head trauma. This is a “radiologically isolated syndrome”, in people who will develop the disease in the coming years (30% develop it within 3 years) or who will never develop it: they are carriers but will not suffer from it. The dilemma then arises: should we look at the images or at the persons who present symptoms and complaints? We will only move forward with the images if we can be absolutely sure that they point to a disease and damage to the person’s integrity. 

There are also patients with a first MS attack, whose MRI reveals some typical, but millimetre-
sized lesions, that will remain unchanged over time. They often are members of a family with an existing case of severe MS. These patients therefore do not need to be treated immediately and aggressively. Instead, they can be monitored, based on regular imaging and the decision to start therapy can be made only if this imaging worsens.

We must therefore be wary of an over-diagnosis of MS based solely on MRI and of over-

treatment in spontaneously non-active and non-progressive forms of this disease. Obviously extensive and active lesions in imaging will also help us to start very aggressive treatments very early and very quickly nip this disease in the bud.

It is here that medicine becomes an art again, based on nuance instead of on algorithms that are blindly applied.