ClinicSpeak: What is the definition of high versus low lesion load on MRI?

Time is brain: what is a high-lesion load on MRI? #ClinicSpeak #MSBlog #MSResearch

"In response to a question from yesterday; what is the definition of a high lesion load on MRI? This is based mainly on data from the so called Queen Square CIS (clinically-isolated syndrome) cohort. These CISers had MRI at baseline and have been followed for over 20 years. The picture below show  a survival analysis of time to EDSS 3.0 or higher (non-benign MS); it is clear the CISers with more than 10 lesions do worse. CISers with no lesions at baseline do the best with very few becoming disabled; in fact 80% of this group never go onto develop MS and hence are unlikely to have MS."

"What is the difference between a CISer sith say 2 lesions at baseline and somebody with 20 lesions? Almost certainly the person with 20 lesions has had the disease longer, with a longer asymptomatic period during which time subclinical inflammation has been shredding their reserve capacity, hence the poorer prognosis on average. Another way of looking at this data is that someone with CIS who presents with a low lesion load is luck in that one of their initial or early lesions has caused symptoms before too much damage has occurred allowing them the possibility of starting DMTs early and giving them a greater chance of becoming NEDA. This strategy of using DMTs as a preventative treatment to preserve reserve capacity and delay all subsequent disability outcomes is not practiced by all; many MSologists, particularly in  the UK, would prefer to allow CISers or MSers to acquire more lesions before starting DMTs. These MSologists often quote that many MSers turn-out to have benign disease hence we need to wait for their disease to progress before treating them. The problem with this argument is that the damage that is acquired whilst waiting is irreversible, reduces reserve capacity and hence shortens their time to future disability end-points. In addition, benign MS is a moving target; the longer you follow benign MSers the smaller the proportion who remain benign."

"So if  you have more than 10 lesions at baseline this is generally considered a high lesion load. The lesion load does not tell the whole story. Some lesions are more destructive than others; the destructive lesions leave behind black holes on the so called T1-weighted scans. Similarly, lesions occurring in the posterior fossa or back of the brain cause more disability than those in the so called superior tentorial compartment of the brain. Active lesions, i.e. those with gadolinium enhancement are also associated  with a poorer outcome compared to inactive lesions. Finally, if there is already end-organ damage with overt brain atrophy this is associated with a poorer prognosis. Therefore, assessing prognosis on MRI is more complicated  than simply counting the lesions."

Table of poor baseline prognostic factors on MRI

  1. High-lesion load (>10 lesions on T2-weighted images)
  2. Presence of gadolinium-enhancing lesions
  3. Posterior fossa lesions
  4. Hypointense lesions on T1-weighted images (black holes)
  5. Overt brain atrophy (end-organ damage) 
"If you have any questions about your MRI scans you should ask your neurologist to go through them with you. Please note if you have a bland looking baseline MRI, with a good prognostic profile, you should consider yourself lucky in that your MS has presented at an early stage before you have acquired any damage. This means that with appropriate monitoring and/or treatment you can potentially preserve your brain's reserve capacity. On the other hand if you have a poor baseline MRI prognostic profile you will need to take your treatment decisions more seriously and have less time to play with. Please remember the dictum 'Time is Brain'."

CoI: multiple

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