Pratique du Shadowing: Ataxia Series: Recognizing sporadic ataxias - Apprendre l'anglais à l'oral avec YouTube

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Hello and welcome to the MTS podcast,

the official podcast of the International Parkinson's Movement Disorder Society.

I am Orlando Barsatini, Professor of Neurology at Federal University of Sao Paulo, Brazil.

And today I'm here with Dr. Divyan Gahr.

Dr. Divyan is Assistant Professor at the Department of Neurology of OutIndia Institute of Medical Science,

New Valley, India.

And today we are discussing sporadic ataxia you can't miss.

Divyanne, thank you for joining us.

Hi, Orlando.

Thank you for having me.

It's truly a pleasure to be here and to discuss such a clinically important topic.

Iviane, my first question, how do you clinically distinguish sporadic from genetic ataxias at the bedside?

And tell me about the diagnostic pitfalls you commonly see in the evaluation of sporadic ataxia.

a great starting point.

At the bedside, I focus on three pillars,

age at onset, the temporal profile of progression of symptoms,

and the family history.

So genetic ataxias usually tend to have an insidious onset.

They tend to be slowly progressive.

And sometimes we find additional neurological features like neuropathy,

pyramidal signs, movement disorders, vision involvement.

It is also important to remember that the absence of family history does not exclude a genetic cause,

which can be due to various reasons like incomplete penetrance,

inaccurate diagnosis in the family member,

subtle symptoms in the family,

or even a small family size or de novo mutations.

So sporadic ataxias, the clues to that are that they usually have an acute to subacute onset,

or they may have a very rapidly progressive course.

And sometimes we will find history of systemic symptoms or history of exposure to drugs,

toxins, which can be great clues.

And some of the common pitfalls include assuming that chronic invariably means degenerative ataxia.

That is not true because we know for many of these sporadic ataxias,

a longer history may still be a part of the clinical spectrum.

Another pitfall is to miss sensory ataxia and assume

that all ataxia is actually cerebellar because sensory ataxias have a different set of etiologies.

Another pitfall would be to overlook medications that patient may be on and not screening adequately for immune or metabolic causes.

So the key principle is to never label degenerative or hereditary before excluding treatable causes.

As you said, we have many groups,

many different groups of sporadic taxis,

including infectious, metabolic, and ultimune.

Could you talk a little bit more about the treatable forms?

Yes, Orlando, absolutely.

And this is really the heart of the matter

because sporadic ataxias should always be approached with the mindset that it may be treatable unless proven otherwise.

So the treatable causes, as you have mentioned,

can be broadly categorized into immune-mediated causes.

Particularly important in these are the anti-GAD-associated ataxia,

gluten ataxia, the paraneoplastic cerebellar degenerations,

The infectious causes which are continuing to be important in some parts of the world,

for example, ataxias occurring in the setting of HIV,

syphilis, Whipple's disease, and then the JC virus which can cause progressive malifocal leucal encephalopathy,

which can occur either in immunocompromised or immunocompetent settings.

And then in children, the post-infectious cerebellitis is important,

which can follow several viral infections.

And then metabolic and nutritional causes,

of course, you must always screen for vitamin deficiencies and some specific electrolyte disturbances.

Toxins are important, particularly alcohol continues to remain the most common cause globally.

But it is also important to consider certain medications,

particularly the anti-seizure medications, chemotherapy agents.

And last but not the least,

I would also mention the structural causes like the tumors,

strokes, demyelinating disorders like multiple sclerosis,

etc. because these can be remedied either surgically or medically.

So if I had to summarize the approach to treatable sporadic ataxias,

I would emphasize three clues.

Of course, the subacute or rapidly progressive temporal profile,

the presence of systemic or extracerebellar features,

and a disproportion between clinical severity and imaging,

which we can talk about a little later.

Okay.

Diviani, when should clinicians suspect immune-mediated cerebral arotaxis?

And could you mention some clinical or radiological clues for this vaginosis,

especially immune-mediated cerebral arotoxic?

Yeah.

This is a crucial question because immune-mediated cerebellar ataxias are actually a very time-sensitive and potentially treatable cause of sporadic ataxia.

The earlier we intervene in these conditions,

the better is the neurological outcome because once cerebellar atrophy becomes evident and established,

reversibility tends to decline significantly.

So the clinicians should suspect immune-mediated etiologies primarily when the evolution is subacute,

meaning the clinical symptoms progress over a few weeks to a few months.

So a patient may report a history that they were walking normally three months ago,

let's say, and they are now needing support.

So that should immediately raise concerns for a potential immune-mediated etiology.

Other clues could be a presence of a personal or a family history of autoimmune disorders.

For example, there could be a family member who has autoimmune thyroid disorders,

type 1 diabetes, vitiligo, pernicious anemia,

celiac disease, etc. And then if you have the presence of some other associated neurological features like seizures,

myoclonus, stiff person syndrome, peripheral neuropathy,

behavioral changes, all of these raise clinical clues towards suspecting immune-mediated cerebellar ataxias.

You also asked about the radiology.

So from the radiological standpoint,

there's an important teaching point that the MRI of the brain can actually be completely normal in the early stages.

So therefore, normal MRI does not exclude immune mediated etiologies.

Okay, great.

Divyani, sometimes gluten ataxia is a controversial topic.

What features suggest gluten ataxia?

And in your vision, what are the most important diagnostic and treatment challenges in gluten ataxia?

Yes, Orlando.

Gluten ataxia is indeed one of the most debated areas in sporadic ataxias.

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I do agree with you.

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So basically, it's an immune-mediated cerebellar condition which is triggered by gluten sensitivity and can often occur independent of the gastrointestinal symptoms.

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In fact, many patients may not have the classic features of celiac disease.

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Clinically, one can suspect gluten ataxia in somebody who has a sporadic progressive cerebellar condition with predominantly a midline ataxia.

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So there is predominantly gait and truncal ataxia,

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a relatively pure cerebellar syndrome,

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or sometimes one may have coexisting peripheral neuropathy or myoclonus.

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The MRI may show vermeon predominant atrophy,

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but as I told you earlier,

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the early imaging may be normal.

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So a good clue here becomes to look at the MR spectroscopy of the vermis,

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which may show a reduced NAA is to creatinine ratio.

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And like you mentioned, the challenges are actually substantial in gluten ataxia.

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The antibody testing is imperfect.

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We rely on a whole host of antibodies

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and there is a lot of debate about which antibodies are most neurologically relevant as opposed to most gastrointestinally relevant.

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Then there are patients who may be zero negative but they are very clinically concerning for gluten.

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So this may raise challenges about whether to initiate a strict gluten-free diet

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or not and there are no universally standardized diagnostic criteria for gluten ataxia.

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So that creates a problem itself.

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Diviani, now I have another sensitive point in the study of ataxia.

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What pathophysiological mechanism explains selective cerebellar degenerative in nutritional deficient related A-tacta?

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And which deficients are the most frequently overlooked in the clinical practice?

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This is a fascinating and a very important area.

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So the cerebellum, as you know,

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especially the the Purkinje cells,

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they are metabolically highly active and they are particularly vulnerable to metabolic stress.

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So these neurons have extensive dendritic connections and they have very high firing rates.

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So that makes them especially sensitive to mitochondrial dysfunction,

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oxidative stress or any other form of energy deficit.

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So nutritional deficiencies tend to interfere either directly or indirectly with these pathways.

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And some of the commoner nutritional deficiencies are triggered by thymine deficiency

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that may occur in the setting of chronic alcohol use but that's pretty well known.

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But some of the less common or overlooked deficiencies might be deficiency of vitamin b12,

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copper and vitamin E all of which tend to cause sensory ataxia rather than cerebellar ataxia.

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And another important deficiency which we should think of particularly

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when there is a setting of chronic vomiting or proton pump inhibitor use

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or a GI surgery would be a deficiency of magnesium.

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And this is a really important cause of cerebellar ataxia,

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where patients can present with severe ataxia,

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classically with a downbeating nystagmus.

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And the MRI may show a typical involvement of the nodulus,

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or it may show cerebellar vasogenic edema.

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It's really important to recognize magnesium deficiency because quick supplementation can lead to dramatic recovery.

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Divini, another important point is sporadic cataxia are quite complex.

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Which toxic or drug-induced ataxia are commonly overlooked in the clinical practice.

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I believe that this is a quite important point.

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I absolutely agree with you because drug-induced and toxic ataxias are probably more common than we recognize,

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and they are very frequently reversible if they're recognized early.

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So, of course, chronic alcohol exposure,

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it is difficult to overlook it,

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but sometimes patients may minimize intake,

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So it's important to be careful and take a non-judgmental history.

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It's important to recognize this because it can lead to permanent cerebellar damage, alcoholic cerebellar degeneration.

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But in terms of the drug,

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some of the important drugs that I want to talk about are the anti-seizure medications.

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So we do know that the older generation anti-seizure medications like phenytoin,

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babichirates, benzodiazepines, and all of that can result in cerebellar atrophy.

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And they continue to be used in many regions of the world.

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So chronic exposure to these can lead to permanent cerebellar atrophy.

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But even among the newer antiseizure medications like gabapentin,

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pregabalin, lamotrigine, many of them are known to trigger ataxia,

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vertigo, tremors as side effects.

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The other group of drugs that we must not miss is antibiotics,

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particularly metronirazole, because that is often used for gastrointestinal infections.

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and a high cumulative dose can precipitate subacute cerebellar syndromes.

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And then sometimes we have clear exposures to drugs like lithium,

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chemotherapeutic agents like cytarabine and immune checkpoint inhibitors increasingly that are being used for the treatment of cancer.

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And then in certain occupations,

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one can have heavy metal exposures like mercury or lead.

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So these might be some of the overlooked causes,

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but definitely are eminently reversible with reduction of exposure.

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Divini, how do sensory neuronopathy-associated ataxia alter the diagnostic approach compared,

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for example, with pure cerebellar syndromes?

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This is a very relevant question clinically,

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because profound proprioceptive loss can mimic cerebellar ataxia,

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but the close there would be a worsening of the ataxia in darkness,

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presence of pseudoathetosis and importantly there would be a preservation of the eye movements in speech

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because these two latter are mediated directly by the cerebellum

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so we don't expect these to be abnormal in a proprioceptive pathway dysfunction.

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Nerve conduction studies are essential and it's important to differentiate clinically sensory from cerebellar ataxias

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because of the list of causes for sensory neuronopathy.

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So the usual causes include paraneoplastic syndromes,

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Jogren's syndrome, chemotherapy agents, B12 deficiency,

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and increasingly being recognize the immune mediated neuropathies like the nodalopathies and the paranodalopathies.

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So recognizing sensory ataxia actually shifts the diagnostic work up towards peripheral and systemic causes.

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And which systemic alt-immune or endocrine disorder should be routinely screened for an ex-premate sporoidic ataxia?

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So this really depends on the clinical context,

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but I would routinely screen for thyroid dysfunction,

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antithyroid antibodies, celiac serology, anti-GAD antibodies,

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and then the autoimmune markers,

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paraneoplastic markers, HIV serology, and B12 deficiency.

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So these are relatively low cost tests with a high diagnostic yield in selected patients.

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So this would be a very basic screening for sporadic ataxias.

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Okay.

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And regarding treatment, which clinical or biomarker features predict the immunotherapy response in all the new cerebellar attacks, the DVNA.

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This is a very important question,

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Orlando, because I just want to mention that time is cerebellum.

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So when we initiate therapy early,

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there is a potential to salvage the cerebellar reserve and improve the neurological deficits.

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The predictors to response to immunotherapy,

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as you asked, would include a shorter duration of symptoms,

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a subacute onset, presence of an MRI being normal rather than an MRI showing cerebellar atrophy,

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presence of surface antibodies as compared to the intracellular onconeural antibodies,

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and of course, early treatment initiation.

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Okay.

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Divyami, this is my last question.

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It's probably the most important question.

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What is the diagnostic algorithm for sporadic ataxia that the treatable ones are not missing?

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I think this is the core question.

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So my structured approach is to first confirm whether it's a cerebellar ataxia or a sensory ataxia or a vestibular ataxia.

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This would of course be deciphered by a good history and a clinical examination.

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Determine the temporal profile and progression of symptoms,

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whether it's are rapidly progressive, subacute.

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Then take a targeted history of exposure to drugs and toxins.

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Don't forget this because this sometimes gets overlooked.

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Perform a good MRI of the brain.

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You must also try to see whether radiological involvement is proportionate to the degree of clinical involvement

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because if you find a lot of clinical dysfunction but not so much of radiological findings,

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that's a good clue towards thinking of immune-mediated ataxias.

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Order some basic laboratory screening like we mentioned earlier,

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that is the routines, thyroid functions, vitamin levels.

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Then pursue targeted autoimmune, paraneoplastic,

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or infectious testing depending on the clinical context.

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Also consider genetic testing only after these treatable causes are excluded.

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So the guiding principle is simple,

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exclude reversible causes before labeling the patient with a degenerative disorder.

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Okay, thank you Diviani for sharing these insights and thank you to our listeners for joining us.

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We hope this episode helped you approach sporadic attacks with greater confidence and precision.

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Thank you.

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Thank you, Orlando.

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The views

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and opinions expressed by the participants in this podcast do not necessarily reflect those of the International Parkinson

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and Movement Disorders Society or their affiliated journals,

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Movement Disorders and Movement Disorders Clinical Practice.

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Any disclosures of the participants can be found within the episode description located on the MDS website.

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