シャドーイング練習: Ataxia Series: Recognizing sporadic ataxias - YouTubeで英語スピーキングを学ぶ
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Hello and welcome to the MTS podcast,
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Hello and welcome to the MTS podcast,
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the official podcast of the International Parkinson's Movement Disorder Society.
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I am Orlando Barsatini, Professor of Neurology at Federal University of Sao Paulo, Brazil.
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And today I'm here with Dr. Divyan Gahr.
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Dr. Divyan is Assistant Professor at the Department of Neurology of OutIndia Institute of Medical Science,
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New Valley, India.
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And today we are discussing sporadic ataxia you can't miss.
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Divyanne, thank you for joining us.
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Hi, Orlando.
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Thank you for having me.
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It's truly a pleasure to be here and to discuss such a clinically important topic.
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Iviane, my first question, how do you clinically distinguish sporadic from genetic ataxias at the bedside?
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And tell me about the diagnostic pitfalls you commonly see in the evaluation of sporadic ataxia.
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a great starting point.
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At the bedside, I focus on three pillars,
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age at onset, the temporal profile of progression of symptoms,
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and the family history.
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So genetic ataxias usually tend to have an insidious onset.
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They tend to be slowly progressive.
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And sometimes we find additional neurological features like neuropathy,
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pyramidal signs, movement disorders, vision involvement.
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It is also important to remember that the absence of family history does not exclude a genetic cause,
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which can be due to various reasons like incomplete penetrance,
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inaccurate diagnosis in the family member,
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subtle symptoms in the family,
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or even a small family size or de novo mutations.
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So sporadic ataxias, the clues to that are that they usually have an acute to subacute onset,
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or they may have a very rapidly progressive course.
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And sometimes we will find history of systemic symptoms or history of exposure to drugs,
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toxins, which can be great clues.
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And some of the common pitfalls include assuming that chronic invariably means degenerative ataxia.
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That is not true because we know for many of these sporadic ataxias,
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a longer history may still be a part of the clinical spectrum.
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Another pitfall is to miss sensory ataxia and assume
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that all ataxia is actually cerebellar because sensory ataxias have a different set of etiologies.
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Another pitfall would be to overlook medications that patient may be on and not screening adequately for immune or metabolic causes.
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So the key principle is to never label degenerative or hereditary before excluding treatable causes.
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As you said, we have many groups,
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many different groups of sporadic taxis,
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including infectious, metabolic, and ultimune.
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Could you talk a little bit more about the treatable forms?
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Yes, Orlando, absolutely.
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And this is really the heart of the matter
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because sporadic ataxias should always be approached with the mindset that it may be treatable unless proven otherwise.
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So the treatable causes, as you have mentioned,
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can be broadly categorized into immune-mediated causes.
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Particularly important in these are the anti-GAD-associated ataxia,
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gluten ataxia, the paraneoplastic cerebellar degenerations,
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The infectious causes which are continuing to be important in some parts of the world,
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for example, ataxias occurring in the setting of HIV,
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syphilis, Whipple's disease, and then the JC virus which can cause progressive malifocal leucal encephalopathy,
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which can occur either in immunocompromised or immunocompetent settings.
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And then in children, the post-infectious cerebellitis is important,
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which can follow several viral infections.
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And then metabolic and nutritional causes,
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of course, you must always screen for vitamin deficiencies and some specific electrolyte disturbances.
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Toxins are important, particularly alcohol continues to remain the most common cause globally.
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But it is also important to consider certain medications,
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particularly the anti-seizure medications, chemotherapy agents.
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And last but not the least,
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I would also mention the structural causes like the tumors,
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strokes, demyelinating disorders like multiple sclerosis,
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etc. because these can be remedied either surgically or medically.
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So if I had to summarize the approach to treatable sporadic ataxias,
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I would emphasize three clues.
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Of course, the subacute or rapidly progressive temporal profile,
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the presence of systemic or extracerebellar features,
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and a disproportion between clinical severity and imaging,
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which we can talk about a little later.
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Okay.
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Diviani, when should clinicians suspect immune-mediated cerebral arotaxis?
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And could you mention some clinical or radiological clues for this vaginosis,
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especially immune-mediated cerebral arotoxic?
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Yeah.
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This is a crucial question because immune-mediated cerebellar ataxias are actually a very time-sensitive and potentially treatable cause of sporadic ataxia.
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The earlier we intervene in these conditions,
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the better is the neurological outcome because once cerebellar atrophy becomes evident and established,
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reversibility tends to decline significantly.
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So the clinicians should suspect immune-mediated etiologies primarily when the evolution is subacute,
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meaning the clinical symptoms progress over a few weeks to a few months.
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So a patient may report a history that they were walking normally three months ago,
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let's say, and they are now needing support.
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So that should immediately raise concerns for a potential immune-mediated etiology.
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Other clues could be a presence of a personal or a family history of autoimmune disorders.
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For example, there could be a family member who has autoimmune thyroid disorders,
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type 1 diabetes, vitiligo, pernicious anemia,
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celiac disease, etc. And then if you have the presence of some other associated neurological features like seizures,
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myoclonus, stiff person syndrome, peripheral neuropathy,
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behavioral changes, all of these raise clinical clues towards suspecting immune-mediated cerebellar ataxias.
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You also asked about the radiology.
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So from the radiological standpoint,
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there's an important teaching point that the MRI of the brain can actually be completely normal in the early stages.
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So therefore, normal MRI does not exclude immune mediated etiologies.
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Okay, great.
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Divyani, sometimes gluten ataxia is a controversial topic.
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What features suggest gluten ataxia?
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And in your vision, what are the most important diagnostic and treatment challenges in gluten ataxia?
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Yes, Orlando.
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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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