シャドーイング練習: Ataxia Series: Neuroimaging patterns not to miss in ataxia - 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 Disorders of Life.
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I am Orlando Barsatini, professor of neurology at Federal University of Sao Paulo, Brazil.
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And I'm here today with Dr. Malco Rossi.
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Malco is a movement disorder neurologist and planning institution in Buenos Aires, Argentina.
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And today we are discussing neuroimaging patterns not to miss in ataxia.
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Malco, thank you for joining us.
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Hi, Orlando.
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Thank you for having me.
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Thank you, Malco.
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Malco, this is my first question for you.
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When you first review an MRI for a patient with ataxia,
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what are the key elements you systematically evaluated in these patients?
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The first thing I do is evaluate the cerebellum.
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I assess whether cerebellar atrophy is present,
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and if so, whether it is global or follows a specific pattern,
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such as predominant involvement of the vermis or the cerebellar hemispheres.
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I always examine the cerebellum in the axial, coronal, and sagittal planes.
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So, vermian atrophy and in particular superior cerebellar vermis involvement can be especially helpful in the diagnostic process.
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In some patients, cerebellar volume appears normal on conventional imaging,
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so in these cases, when available,
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T1 volumetric MRI can help confirm the absence of overt cerebellar atrophy or reveal mild volume loss.
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This is particularly relevant because not all causes of ataxia show cerebellar atrophy,
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especially in the early disease stages.
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So, it is also very important to evaluate the cerebellar peduncles.
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Atrophy of the superior cerebellar peduncles can point to specific etiologies,
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and the superior, middle, and inferior peduncles may show T2
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or flare hyperintensities that can be very informative in certain causes of ataxia.
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So, when cerebellar atrophy is present,
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it is often diffuse and nonspecific,
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which limits the diagnostic value in clinical practice.
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For this reason, I then systematically assess for additional MRI abnormalities beyond the cerebellum,
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like brainstem, basal ganglia, corpus gaiosum, and cortical regions.
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Other than atrophy patterns, I carefully look for associated signal abnormalities,
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both hyperintensities and hypointensities that may provide important diagnostic clues,
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as well as any distinctive imaging features that point towards specific etiologies.
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So, in other words, in patients with ataxia,
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the MRI evaluation should follow a structured pattern-based approach rather than focusing only on the cerebellar volume.
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Okay.
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And also, in everyday clinics,
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cerebral atrophy in cerebral antacus is often diffuse and no specific.
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And now some of the most challenging cases are those where cerebral atrophy is minimal and even absent.
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My question, which cerebral imaging features do you find the most helpful in daily practice or in evaluation of these patients?
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The cerebral imaging signs that I find particularly helpful in daily clinical practice are the changes in the cerebral peduncles.
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Cerebellar peduncul hyperintensities are a well-recognized feature of Fragile X-Associated Traumatoxia Syndrome and can also be seen in MSA Type C.
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Also, superior cerebellar peduncul hyperintensity is present in up to 60% of patients with SCAR27B.
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This is a frequent cause of late-onset ataxia,
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either sporadic or familiar, with typical features including onset after age 45,
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downbeat nystagmus, episodic worsening, and symptom exacerbation with caffeine.
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Of importance, SCA27B is a treatable cause of ataxia as many patients respond to 4-aminopiridine.
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So this makes early recognition of this disorder very important.
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Also, another point is that superior cerebellar vermis atrophy can be helpful,
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even though this finding can be seen in some common causes of ataxia,
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such as free text ataxia,
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phenocerebellar ataxias, and also in alcoholic cerebellar degeneration,
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it is also a classic feature of ARSACs,
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particularly when associated with other typical MRI findings of ARSACs,
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like the bilateral hypo-intense pontine stridions and the enlarged pons.
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And as you mentioned, Orlando,
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many causes of ataxia show diffuse and nonspecific cerebellar atrophy,
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and in some conditions, cerebellar atrophy may be minimal or even absent,
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particularly in early disease stages.
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This can occur in Friedreich's ataxia.
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Also in ataxia with vitamin E deficiency in adult-onset Alexander disease are in several hereditary spastic paraplycheas
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that combine spastic paraparasis and ataxia.
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In these cases, cervical spine MRI to assess for spinal cord atrophy can be very helpful.
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So for this reason, I routinely assess atrophy patterns beyond the cerebellum,
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including the brainstem and basal ganglia.
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For example, combined atrophy of the putamen,
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pons, and middle cerebellar peduncles points to MSA type C,
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while midbrain atrophy patterns are characteristic of PSP type C.
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In addition to atrophy, signal abnormalities,
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including hyperintensities in the brainstem,
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spinal cord, basal ganglia, corpus gaiosum,
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inferior o-lifts, or cerebellar white matter,
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often provide critical diagnostic clues,
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particularly early in the disease course.
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A classic example is the hot cross-band sign,
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which is highly specific for MSA type C,
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with an about 98 or 99% specificity,
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but its sensitivity is limited around 45 to 70%.
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So of importance, this sign is not pathognomonic and has been reported in several other conditions,
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including many scars, like SCAL34,
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as well as immune-mediated or panneoplastic,
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inflammatory, vascular, and infectious causes of ataxia.
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This overlap reflects shared pathophysiological mechanisms that include the degeneration of pontine neurons
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and transverse pontocerebellar fibers with relative sparring of the pontine tegmentum and corticospinal tracts.
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Also valerian degeneration and gliosis has been reported and so given the broad list of differential diagnosis for the hot crossband sign,
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the presence of a hot crossband sign needs a clinical correlation,
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taking into account the age at onset,
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disease progression, predominant clinical features,
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laboratory findings, and also additional imaging features.
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But MSA should remain high on the differential diagnosis unless clearly excluded.
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Very clear, Malco.
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Malco, signs like the hot cross band or middle cerebral arthropodical hyperintensive are well known,
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as you already mentioned.
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But probably the most important question here is how do we use these findings in real world clinical decisions made?
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Could You fuck a little bit more.
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Yes, Orlando.
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I use these MRI signs as clues rather than diagnostic endpoints.
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Findings such as the hot crossband sign
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or middle cerebellar peduncle hyperintensities help me narrow the differential diagnosis and give priority to some etiologies,
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but they should never be analyzed in isolation.
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In my clinical practice, I try to integrate MRI findings with a phenotype,
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like age at onset, rate of progression,
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and the presence of specific clinical manifestations like oculomoto signs,
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pyramidal signs, or associated movement disorders.
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I think that some imaging patterns help me guide the next diagnostic step rather than providing a definitive diagnosis on their own.
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Although some MRI signs are highly specific when present,
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their sensitivity is often limited,
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especially in early disease stages,
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which means that they should always be interpreted in a clinical context.
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My diagnostic approach starts with a careful analysis and neurological examination,
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which in many patients with ataxia sometimes provides a very strong diagnostic clue.
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Based on this initial assessment,
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I usually have a short list of differential diagnosis,
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and a brain MRI then helps me refine and narrow that list.
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The combination of clinical and imaging features guides targeted laboratory testing.
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For example, measuring alpha-phytoprotein, which is commonly elevated in ataxia telangiectasia,
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and some forms of ataxia mid-oculumotor apraxia also.
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And also you can also measure vitamin E levels,
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which can also be helpful for the diagnostic process.
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Neuroimaging also directly influences my genetic testing strategy.
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Depending on the clinical neuroimaging pattern,
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I may give priority to testing for repeat expansions versus exam sequencing.
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For instance, superior cerebellar peduncle hyperintensity,
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when associated with the corresponding phenotype,
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raises early suspicions for SCA27b,
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a repeat expansion ataxia, And then a targeted confirmation should be done.
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Middle cerebellar peduncle hyperintensities in an adult onset ataxia with axiom tremor makes me consider Fratex,
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another repeat expansion disorder.
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And also the presence of a hot crossband sign leads me first to think of MSA type C.
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But I also consider other possibilities,
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such as SCAR-34 or immune-mediated ataxias,
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including anti-Homer-3 or anti-Kelch-like protein 11,
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depending on disease cause and associated clinical features.
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In short, neuroimaging signs are most powerful when they are integrated with the clinical picture and used to guide a rational,
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stepwise diagnostic strategy.
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Thank you.
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Welcome.
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For the next question, particularly I like so much this topic,
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some imaging signs look like animal shapes and they are easy to remember.
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Can you name a few examples and how do you use these signs in clinical practice without letting them bias your diagnosis?
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Yes, both neurologists and neuroradiologists can sometimes experience visual pareidolia,
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which is the tendency to perceive meaningful shapes,
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often animals or faces, in random or ambiguous visual patterns.
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I experienced this a few years ago
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when a resident asked me to evaluate an MRI of a patient with cerebellar ataxia and unilateral cerebellar hyperintensity.
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At first glance, the lesion immediately reminded me of a shrimp.
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So the shrimp sign had already been described,
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and this is a unilateral lesion in the cerebellar white matter outlining the dentate nucleus.
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This sign is a reliable indicator of progressive multifocal leucencephalopathy in patients with rapidly progressive cerebellar ataxia.
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And the patient was evaluated and was finally diagnosed with progressive multifocal leucencephalopathy based on disease characteristic and laboratory findings.
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Other examples of imaging signs
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that look like animal's shapes include the crab sign described in SCAV-48
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that is characterized by dentate nucleus T2 hyperintensities and predominant posterolateral cerebellar hemispheric atrophy.
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Also the cat pole sign showing marked atrophy of the medulla oblongata and cervical spinal cord with a relatively preserved pons.
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This is a typical adult-onset Alexander disease finding.
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And the face of the giant panda is classically associated with Wilson's disease,
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a condition in which ataxia can be present in some patients,
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but it has also been reported in isoniazid-induced ataxia.
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In the cerebellar variant of PSP,
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midbrain atrophy patterns, such as the hummingbird and mouse sign,
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show very high specificity, although some sensitivity is limited in early stages.
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Also, even well-known signs like the eye of the tiger,
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typically linked to PANC2.
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They have also been reported in SCAD28.
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So to sum up, recognizable imaging animal patterns can clearly speed up diagnosis,
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but they should never be interpreted in isolation.
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Only by integrating MRI findings with clinical futures,
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demographics, and laboratory data can we confidently identify typical phenotypes of genetic and acquired ataxias.
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Okay.
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Thank you, Marcus.
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Sometimes for me, it's quite difficult to identify these animal shapes on the brain MRI.
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Here I have my last question.
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How do you see advanced MRI techniques,
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nuclear imaging to earlier diagnosis,
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disease monitoring, and the future clinical trials in ataxia?
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I think, Orlando,
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that neuroimaging will increasingly shift from a purely diagnostic tool to quantitative biomarker of disease progression and also treatment response.
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We are moving beyond visual pattern recognition to measurable and reproducible metrics,
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and advanced MRI techniques such as volumetry and diffusion imaging or DTI can detect in the research setting very early,
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even preclinical changes, and allow us to track progression more sensitively than clinical scales alone.
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Of importance, mild cerebellar and brainstem volume loss has been shown in persons with spinocerrebellar ataxias like SCA1,
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2, 3, and 6, even before ataxia develops.
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I think that also nuclear imaging,
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while still emerging in ataxias,
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it has the potential to capture the disease biology,
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such as neuroinflammation or synaptic dysfunction.
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I think that together these tools will be very important for early diagnosis,
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patient stratification and outcome measures in future clinical trials.
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Okay.
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Thank you, Marco, for sharing these insights and thank you to our listeners to join us.
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We hope this episode helps you approach ataxia imaging with greater confidence and precision.
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Thank you.
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Thank you, Arlasa.
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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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