تدريب Shadowing: Ataxia Series: Neuroimaging patterns not to miss in ataxia - تعلم التحدث بالإنجليزية مع YouTube

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Hello and welcome to the MTS podcast,

the official podcast of the International Parkinson's Movement Disorders of Life.

I am Orlando Barsatini, professor of neurology at Federal University of Sao Paulo, Brazil.

And I'm here today with Dr. Malco Rossi.

Malco is a movement disorder neurologist and planning institution in Buenos Aires, Argentina.

And today we are discussing neuroimaging patterns not to miss in ataxia.

Malco, thank you for joining us.

Hi, Orlando.

Thank you for having me.

Thank you, Malco.

Malco, this is my first question for you.

When you first review an MRI for a patient with ataxia,

what are the key elements you systematically evaluated in these patients?

The first thing I do is evaluate the cerebellum.

I assess whether cerebellar atrophy is present,

and if so, whether it is global or follows a specific pattern,

such as predominant involvement of the vermis or the cerebellar hemispheres.

I always examine the cerebellum in the axial, coronal, and sagittal planes.

So, vermian atrophy and in particular superior cerebellar vermis involvement can be especially helpful in the diagnostic process.

In some patients, cerebellar volume appears normal on conventional imaging,

so in these cases, when available,

T1 volumetric MRI can help confirm the absence of overt cerebellar atrophy or reveal mild volume loss.

This is particularly relevant because not all causes of ataxia show cerebellar atrophy,

especially in the early disease stages.

So, it is also very important to evaluate the cerebellar peduncles.

Atrophy of the superior cerebellar peduncles can point to specific etiologies,

and the superior, middle, and inferior peduncles may show T2

or flare hyperintensities that can be very informative in certain causes of ataxia.

So, when cerebellar atrophy is present,

it is often diffuse and nonspecific,

which limits the diagnostic value in clinical practice.

For this reason, I then systematically assess for additional MRI abnormalities beyond the cerebellum,

like brainstem, basal ganglia, corpus gaiosum, and cortical regions.

Other than atrophy patterns, I carefully look for associated signal abnormalities,

both hyperintensities and hypointensities that may provide important diagnostic clues,

as well as any distinctive imaging features that point towards specific etiologies.

So, in other words, in patients with ataxia,

the MRI evaluation should follow a structured pattern-based approach rather than focusing only on the cerebellar volume.

Okay.

And also, in everyday clinics,

cerebral atrophy in cerebral antacus is often diffuse and no specific.

And now some of the most challenging cases are those where cerebral atrophy is minimal and even absent.

My question, which cerebral imaging features do you find the most helpful in daily practice or in evaluation of these patients?

The cerebral imaging signs that I find particularly helpful in daily clinical practice are the changes in the cerebral peduncles.

Cerebellar peduncul hyperintensities are a well-recognized feature of Fragile X-Associated Traumatoxia Syndrome and can also be seen in MSA Type C.

Also, superior cerebellar peduncul hyperintensity is present in up to 60% of patients with SCAR27B.

This is a frequent cause of late-onset ataxia,

either sporadic or familiar, with typical features including onset after age 45,

downbeat nystagmus, episodic worsening, and symptom exacerbation with caffeine.

Of importance, SCA27B is a treatable cause of ataxia as many patients respond to 4-aminopiridine.

So this makes early recognition of this disorder very important.

Also, another point is that superior cerebellar vermis atrophy can be helpful,

even though this finding can be seen in some common causes of ataxia,

such as free text ataxia,

phenocerebellar ataxias, and also in alcoholic cerebellar degeneration,

it is also a classic feature of ARSACs,

particularly when associated with other typical MRI findings of ARSACs,

like the bilateral hypo-intense pontine stridions and the enlarged pons.

And as you mentioned, Orlando,

many causes of ataxia show diffuse and nonspecific cerebellar atrophy,

and in some conditions, cerebellar atrophy may be minimal or even absent,

particularly in early disease stages.

This can occur in Friedreich's ataxia.

Also in ataxia with vitamin E deficiency in adult-onset Alexander disease are in several hereditary spastic paraplycheas

that combine spastic paraparasis and ataxia.

In these cases, cervical spine MRI to assess for spinal cord atrophy can be very helpful.

So for this reason, I routinely assess atrophy patterns beyond the cerebellum,

including the brainstem and basal ganglia.

For example, combined atrophy of the putamen,

pons, and middle cerebellar peduncles points to MSA type C,

while midbrain atrophy patterns are characteristic of PSP type C.

In addition to atrophy, signal abnormalities,

including hyperintensities in the brainstem,

spinal cord, basal ganglia, corpus gaiosum,

inferior o-lifts, or cerebellar white matter,

often provide critical diagnostic clues,

particularly early in the disease course.

A classic example is the hot cross-band sign,

which is highly specific for MSA type C,

with an about 98 or 99% specificity,

but its sensitivity is limited around 45 to 70%.

So of importance, this sign is not pathognomonic and has been reported in several other conditions,

including many scars, like SCAL34,

as well as immune-mediated or panneoplastic,

inflammatory, vascular, and infectious causes of ataxia.

This overlap reflects shared pathophysiological mechanisms that include the degeneration of pontine neurons

and transverse pontocerebellar fibers with relative sparring of the pontine tegmentum and corticospinal tracts.

Also valerian degeneration and gliosis has been reported and so given the broad list of differential diagnosis for the hot crossband sign,

the presence of a hot crossband sign needs a clinical correlation,

taking into account the age at onset,

disease progression, predominant clinical features,

laboratory findings, and also additional imaging features.

But MSA should remain high on the differential diagnosis unless clearly excluded.

Very clear, Malco.

Malco, signs like the hot cross band or middle cerebral arthropodical hyperintensive are well known,

as you already mentioned.

But probably the most important question here is how do we use these findings in real world clinical decisions made?

Could You fuck a little bit more.

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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you

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