Bluesky, I appreciate your posts - they usually make me think and have to look things up that I have forgotten.
It's tough to know why a doc does something. But I can speak to the research on this topic, which almost all neurologists rely on. MRI and MS are far too complex for us to fully understand (unless it’s our job, and even then...). A more detailed answer is therefore long! So please forgive the length. (even what I write below will likely be missing a dozen other factors I haven’t thought of or learned).
In all the scenarios you noted, it's impossible for us to know what the doc was thinking. First, because we are missing the 5-6 years of post-med school training specifically in neurology and the experience with 1000s of patients. But also, even other neurologists would never attempt to explain another neuro's decision without actually examining the patient and seeing all their history and results.
Willowford, if you would be so kind, I am very interested in some specific issues regarding lesions and MRI.
* Some doctors diagnose people with MS even if their MRI is completely clear. Therefore that must mean that some people can have flare-ups and disability and progression that is not reflected on their MRI. How is this consistent with the definition of MS?
I can’t even begin to discuss the complexity of diagnosing MS (may sound simple to a bystander) here, because it is a heavily multifaceted issue.
Briefly, various diagnostic criteria have come and gone over the years. You might know that MS used to be a purely clinical diagnosis (based on symptoms). And even then, it wasn’t that simple. The available categories were “probable MS”, “possible MS” and “unlikely MS”. Even as recent as the 80s-90s, the criteria for MS was heavily based on clinical symptoms (See Poser criteria).
Now that MRI is universally adopted, neuros use the McDonald criteria for diagnosis, which relies on both clinical presentation AND other findings such as MRI. (See McDonald criteria revised for 2005 version). Even this new criteria has its limitations (as with everything in life). This criteria requires MRI confirmation of lesion (lesion must also be "disseminated" in time and space).
In your scenario, one possibility of the individuals you're referring to is if they were diagnosed before this criteria was established (2001) or used in their country; their neuro may have diagnosed based on symptoms only.
Or the diagnosis was so classic of MS, that the doc decided to let the patient know before getting the MRI back – which might spare them the agony of waiting.
Keep in mind the possibility of a misunderstanding between what the doc meant to say (or said) and what the patient heard (or understood or relayed to others). <-- I have seen this often.
* Some doctors believe that unless you have a corresponding lesion on your MRI that directly reflects clinical symptoms you are presenting, then you are not having MS activity, and therefore your symptoms cannnot be from MS. And yet in support groups, patient after patient will share their stories of how annoying this is. Is this a case of an incorrect assumption from the doctors, or just a few uninformed doctors, or something else entirely?
I’m just imagining a patient going in with severe new symptoms and being told it’s not their MS flare-up without further treatment or investigations as to what it is. How frustrating! I hope this isn't everyone's experience.
A few things that we know from the literature that the doctor MAY be relying on:
1) A clinical relapse is caused by something NEW going on in the brain (currently, white matter lesions are believed to underlie relapses). If there’s truly no brain abnormality, then one is not having a relapse. HOWEVER, just because we can’t see lesions on the MRI, doesn’t mean they aren’t there... so relying on them exclusively and ignoring the clinical aspects has been criticized by some experts. Also, there are other factors than white matter lesions than may be involved (more on this coming up).
2) Doc may be thinking patient is having a "pseudo-exacerbation": refers to recurrence of old symptoms (nor reflecting “new brain damage”), short duration of symptoms (not characteristic of a true relapse), and other health problems not related to MS leading to worsening of symptoms (e.g., urinary tract infection in women can lead to urinary frequency, which mimics the symptoms of an MS attack). Just because a person has MS doesn’t mean that all their symptoms are going to be due to an attack. If the neuro doesn't think it's MS-related, then it would be reasonable to rule out other probs with the family doc.
* Some doctors believe that the MRI does not correlate to the clinical picture and they use it as a general snapshot every few years but they don't try to exactly match presenting symptoms to specific MRI lesions. Are these doctors doing it right? Why the different approaches? Is there a consensus behind the scenes?
The doctors’ beliefs you noted are likely based on studies of patients with MS whose symptoms were measured and recorded over time and compared to their MRI scans to see the degree of correlation.
The correlation between symptoms and MRI white matter lesions (the ones we see with standard MRIs used for clinical purposes) is weak to modest. The specific value depends on which symptom we’re talking about. These lesions also have weak to modest relationships with disease progression. But weak to modest relationship means that there IS a connection, it's just not perfect. This also tells us that there is other things going on in the brain (more below).
If brain abnormalities are the immediate cause of symptoms, then why isn't the association between lesions and symptoms perfect?
1) Imaging technology: it has improved greatly, but not yet enough for us to see everything. For instance, for clinical purposes 1.5-T MRI is used. In research, the newer 3T is used, and shows better anatomical details (it's being introduced now for clinical purposes, at least in North America). Even that won't show everything though.
2) White matter lesions reported in clinics are not the only factors related to symptoms. First, there’s different types of lesions meaning different things (hypointense, hyperintense, etc). Then, there’s all sorts of other measures that we know of through studies using different imaging techniques (diffuse white matter damage, brain volumes, gray matter atrophy...etc), some of which are measured by other methods than MRI. Some of these are independent of lesions.
And we now know that even “normal-appearing” grey or white matters have subtle abnormalities that are not reported in standard clinical reports. They are in fact called “normal-appearing” because they appear normal on most MRI scans.
One of many good sources on some of this stuff is Grassiot, Desgranges, Eustache, & Defer (2009)
So docs do rely on info about white matter lesions available to them, but realize that it's not the full picture. If we include all of the various known brain factors into the equation, we would get a better correlation between the MRI picture and symptoms (and studies so far have confirmed this). But even then, it would not be perfect until we know everything about all the things going on in the brain to lead to symptoms.
* Some people never have enhancing lesions. Never. If one of the hallmarks of active disease is a breach of the BBB, shouldn't there be enhancement sometime? Many MS doctors do not seem troubled by this, and yet this seems to go against the concept of the definition, just the same way that a clear MRI would.
Shall I go on?
Is it the end of the semester yet?
Gd-enhanced lesions usually reflect "new" lesions (less than 6 weeks). Later on, they will appear different on MRI. This may be one explanation to your scenario.
As I mentioned, there are different types of lesions, so there are patients who have cortical lesions (shown in diffusion MRI and other measures) that never show up as Gd enhanced lesions. These lesions are different than typical white matter subcortical ones.
Again, if the patient is not well-versed in MRI technology (most of us are not), then the issue of miscommunication and misinterpretation comes to mind here too.