Spinocerebellar ataxia

1. Spinocerebellar ataxia
Tanat Tabtieang MD
D e p a r t m e n t o f R a d i o l o g y
F a c u l t y o f M e d i c i n e
C h u l a l o n g k o r n U n i v e r s i t y

2.  Severe atrophy of bilateral cerebellar hemisphere and vermis
Mild atrophic change of basal pons and bilateral middle cerebellar
peduncles
T1WI T1WI + Gd

3.  Severe atrophy of bilateral cerebellar hemisphere and vermis
Mild atrophic change of basal pons and bilateral middle cerebellar
peduncles
T1WI T2WI FLAIR

4.  Severe atrophy of bilateral cerebellar hemisphere and vermis
Mild atrophic change of basal pons and bilateral middle cerebellar
peduncles
T1WI T2WI FLAIR

5.  Severe atrophy of bilateral cerebellar hemisphere and vermis
Mild atrophic change of basal pons and bilateral middle cerebellar
peduncles
T1WI T2WI FLAIR

6.  No restricted fluid diffusion on DWI and ADC
 No hemorrhagic focus or abnormal paramagnetic substance
deposition
ADCDWI SWI

7.  No abnormal parenchymal, dural or leptomeningeal enhancement.
T1WI T1WI + Gd

8. Imaging findings
 Severe atrophy of bilateral cerebellar hemispheres and vermis with
mild atrophic change of basal pons and bilateral middle cerebellar
peduncles.
 Cervicomedullary junction and included C-spine appear normal size
and SI.
 The rest brain parenchyma shows normal SI.
 No hemorrhagic focus or abnormal paramagnetic substance
deposition is detected
 No extra-axial collection or shifting of midline structures.
 No abnormal parenchymal, dural or leptomeningeal enhancement.

9. Cerebellar atrophy
• Multiple System Atrophy (MSA)
• Spinocerebellar ataxia (SCA)
• Alcohol intoxication
• Prolonged phenytoin/phenobarbital use
• Chronic vertebrobasilar insufficiency
• Paraneoplastic syndrome
• Hypothyroidism
• Radiation and chemotherapy
Clinical history often more important in making diagnosis than imaging findings

10. Multiple system atrophy
 A neurodegenerative disorder that affects cerebellar, extrapyramidal,
and autonomic systems.
 Cerebellar ataxia, parkinsonism, and autonomic failures.
 MRI findings
◦ cerebellar atrophy accompanied by dilatation of fourth ventricle
◦ atrophy of the brainstem (predominantly in pontine base)
◦ “hot cross bun” sign: loss of myelinated transverse pontocerebellar fibers

11.  (A) In the sagittal T1-weighted MR image, atrophy of the pons is more
prominent in the pontine base than in the pontine tegmentum.
 (B) Axial T2-weighted MR image shows cruciform hyperintensity (“hot
cross bun” sign) in the pons. Middle cerebellar peduncles are also
atrophied, with high-signal-intensity lesions.

12.  (A) Axial T2-weighted MR image in a patient with MSA-C shows atrophy of the pons
with cruciform hyperintensity (“hot cross bun” sign).
 (C) Klüver-Barrera (KB) staining section of the pons from normal control.
 (D) KB staining section of the pons from a patient with MSA-C (the same case as
Panel B) shows atrophy of the pons and marked reduction of the myelinated fibers
including transverse pontocerebellar fibers.

13. Spinocerebellar ataxia
 Autosomal dominant disorders
 Cerebellum and cerebellar interconnection neurodegeneration
 Severe atrophy of posterior fossa structures and variable atrophy of
basal ganglia nuclei, pyramidal tract and cortical areas at end stage
 MR imaging makes it possible to follow changes of brain structures of
SCA patients during life
 MR imaging cannot predict the specific genotype of SCA that was
diagnosed clinically.
 However, MR imaging may help to separate SCA from sporadic or
recessive ataxias and may cluster SCAs into groups, resulting in
suggestions or a stepwise procedure for genetic testing.

15. Spinocerebellar ataxia type 3
 Most common hereditary SCA in worldwide
 Expansion of a CAG repeat in the ataxin-3 gene
 Younger onset: cerebellar ataxia, spasticity, and dystonia
 Older onset: cerebellar ataxia, polyneuropathy, and ophthalmoplegia
 MRI abnormalities are difficult to detect in the early stage of SCA3
◦ atrophy in the pontine tegmentum
 In the later stage, brainstem and cerebellar atrophy will be clear
◦ Linear high-intensity-signal lesion in the midline of pons coursing an
anteroposterior direction in T2WI
◦ early change of “hot cross bun” sign.
 Neurons of the pontine nuclei are slightly shrunken, but the cell
architecture is well preserved  Myelinated transverse pontocerebellar
fibers are preserved, loss of these fibers only in the midline of pons where
the fibers coming from the left and right pontine nuclei cross

17.  (A) Sagittal T1-weighted MR image shows mild atrophy of the pons (particularly in
the pontine tegmentum) and cerebellum.
 (B) The pontine tegmentum is defined as the dorsal area of the pons between the
medial lemniscus and the base of the fourth ventricle (between the arrows).
 (C) Axial T2-weighted MR image shows mild atrophy of the pons and cerebellum.

18.  (B) Axial T2-weighted MR image in a patient with SCA3 shows atrophy of the pons with
linear high-intensity-signal lesion in the midline of pons coursing an anteroposterior
direction.
 (C) Klüver-Barrera (KB) staining section of the pons from normal control.
 (E) KB staining section of the pons from a patient with SCA3 (the same case as Panel C)
shows marked atrophy of the pons. Although loss of myelinated fiber is very mild
compared with the MSA-C, it is also observed in the midline of pontine base (arrow).

19. Spinocerebellar ataxia type 1
 An autosomal dominant SCA
 Expansion of a CAG repeat in the ataxin-1 gene
 Cerebellar ataxia, spasticity, increased tendon reflexes, cognitive
impairment, and ophthalmoplegia.
 MRI findings are atrophy of the brainstem and cerebellum which
resemble those of SCA3.
 Linear high-intensity-signal lesion in the midline of pons coursing an
anteroposterior direction in T2WI.

21.  (A) Sagittal T1-weighted MR image shows atrophy of the cerebellum and
brainstem.
 (B) Axial T2-weighted MR image shows atrophy of the cerebellum,
brainstem, and middle cerebellar peduncles. In the pons, linear high-
intensity signal lesion in the midline of pons is slightly observed (arrow).

22. Spinocerebellar ataxia type 2
 Cerebellar ataxia, slow saccadic eye movement, involuntary movement
(such as myoclonus, dystonia), dementia, and polyneuropathy.
 Expansion of a CAG repeat in the ataxin-2 gene.
 Brain MRI show prominent atrophy of the brainstem and cerebellum.
 Atrophy of the pons is more prominent in the pontine base than in the
pontine tegmentum
 “Hot cross bun” sign is observed in the pons on axial T2-weighted MR
images
 MRI findings of SCA2 are quite similar to those of MSA-C.
◦ When a young patient shows on MRI findings resembling to MSA-C, we
should consider a possibility of SCA2.

24.  (A) Sagittal T1-weighted MR image shows atrophy of the cerebellum and brainstem
associated with dilatation of the fourth ventricle. Similar to MSA-C, atrophy of the
pons is more prominent in the pontine base than in the pontine tegmentum.
 (B) Axial T2-weighted MR image show atrophy of the cerebellum and brainstem,
and “hot cross bun” sign. High-intensity-signal lesions are slightly showed in the
middle cerebellar peduncles.

25. Spinocerebellar ataxia type 6
and 31
 Autosomal dominant SCA
 Exhibit late-onset pure cerebellar phenotype.
 Cardinal symptom is cerebellar ataxia, occasionally mild dystonia in the
limbs
 SCA 6: Small expansion of a CAG repeat in the alpha1A-voltage-dependent
calcium channel gene
 SCA31: 2.5- to 3.8-kb insertion containing pentanucleotide repeats within
an intron of the BEAN gene
 MRI findings: cerebellar atrophy without brainstem and cerebral
involvement
 Unable to distinguish between SCA6 and SCA31 clinically or radiologically.

27. SCA 6
 (A) Sagittal T1-weighted MR image shows atrophy of the cerebellar
hemispheres and vermis.
 (B) (C) Axial T2-weighted MR images show atrophy of the cerebellum
without brainstem and cerebral involvement.

28. SCA 31
 (A) Sagittal T1-weighted MR image shows atrophy of the cerebellar
vermis.
 (B) Axial T2-weighted MR image shows atrophy of the cerebellum
without brainstem and cerebral involvement.

29. Dentatorubral pallidoluysian
atrophy (DRPLA)
 Autosomal dominant spinocerebellar ataxia caused by the expansion of a
CAG repeat in the atrophin-1 gene
 On MR imaging, atrophy of the brainstem and cerebellum are common
findings.
 Atrophy of the pons is more prominent in the pontine tegmentum than in
the pontine base.
 Adult-onset group
◦ high-signal-intensity lesions are observed in the cerebral white matter, brainstem,
and thalamus on T2WI
 Juvenile-onset group
◦ signal abnormalities in the cerebral white matter are usually absent (or
periventricular white matter changes appear in themost advanced stage).
◦ Severe cerebral atrophy is a characteristic finding in juvenile-onset group
◦ Cerebral atrophy in juvenile-onset group may correlate to the severe dementia
and epilepsy

30. DRPLA (adult-onset group).
 (A) Sagittal T1-weighted MR image shows atrophy of the cerebellum and
brainstem.
 (B) (C) (D) Axial T2-weighted MR images show high-signal-intensity lesion in the
cerebral white matter and pons, in addition to atrophy of the cerebellum.

31. DRPLA (juvenile-onset group).
 (A) Sagittal T1-weighted MR image shows atrophy of the cerebellum, brainstem, cerebral
hemisphere, and corpus callosum.
 (B) (C) (D) Axial T2-weighted MR images show prominent atrophy of the cerebral hemispheres, in
addition to atrophy of the cerebellum. Involvement of the cerebral white matter is not clear.

32. Progressive Nonfamilial Adult Onset
Cerebellar Degeneration

33. Alcoholic encephalopathy
 Alcoholic encephalopathy
◦ Disproportionate superior vermian atrophy
◦ Cerebral hemispheres, especially frontal lobes
◦ Increased size of cerebral sulci, interhemispheric/sylvian fissures
◦ Enlargement of lateral ventricles, sulci with chronic alcoholic encephalopathy
◦ Nonspecific multifocal white matter hyperintensities
◦ Less common: Diffuse white matter hyperintensity from toxic demyelination
 Wernicke encephalopathy
◦ Mammillary body, medial thalamus, hypothalamus, periaqueductal gray
abnormal signal/enhancement/diffusion restriction
 Marchiafava-Bignami disease
◦ Abnormal signal and later necrosis in corpus callosum

34. Sagittal graphic shows generalized and superior vermian atrophy, as well as necrosis in the corpus callosum related
to alcoholic toxicity. Mammillary body, periaqueductal gray necrosis is seen with Wernicke encephalopathy.
Sagittal T1WI MR shows the classic finding of significant cerebellar atrophy (white solid arrow) with supratentorial
parenchyma that appear normal
Coronal T2WI MR demonstrates pronounced cerebellar atrophy.

35. Axial T2WI MR shows the classic finding of significant cerebellar atrophy (white solid
arrow), evidenced as prominent folial spaces, with normal appearing supratentorial
parenchyma.

36. Chronic phenytoin use
 Dilantin vs. seizures as cause of atrophy debated
 Dilantin induces organic cerebellar damage & may interfere with
intestinal absorption of folate causing folate deficiency → cerebellar
atrophy
 Seizures can cause cerebellar atrophy as cerebellum is very sensitive to
hypoxia → cerebellar atrophy
 Normal orientation & anisotropy of middle cerebellar peduncle &
transverse pontine fibers

37. Coronal T2WI MR demonstrates significant diffuse cerebellar atrophy (white
solid arrow)
Axial T1WI MR demonstrates significant diffuse cerebellar atrophy (white solid
arrow)

38. Paraneoplastic syndrome
 Remote neurological effect(s) of cancer, associated with extra-CNS
tumors
 Most common tumor: Small cell lung carcinoma
 Limbic encephalitis: Hyperintensity in mesial temporal lobes, limbic
system
◦ Mimics herpes encephalitis but subacute/chronic
 Paraneoplastic cerebellar degeneration (PCD): Cerebellar atrophy
 Brainstem encephalitis: T2 hyperintensity in midbrain, pons, cerebellar
peduncles, basal ganglia
 Most paraneoplastic syndromes do not have associated imaging
findings

39. Axial FLAIR and T2WI MR demonstrates bilateral hyperintensities (white solid arrow) of paraneoplastic
cerebellitis, which will likely result in cerebellar degeneration.

40. Hypothyroidism
 Pituitary hyperplasia (PH)
◦ Symmetrical pituitary enlargement that is reversible with thyroid hormone
replacement therapy (THRT)
 Basal ganglia variably hyperintense (Ca++)
 Hashimoto encephalopathy (HE)
◦ Bilateral patchy or confluent subcortical and periventricular white matter
(WM) T2 hyperintensity with relative sparing of occipital lobes, bilateral and
symmetric or unilateral mesial temporal lobe edema
 Hashimoto thyroiditis-associated ataxia
◦ Cerebellar vermis or olivopontocerebellar atrophy

41. Axial FLAIR MR shows T2 confluent hyperintensity of leukoencephalopathy (white solid
arrow) of cerebellar peduncles & temporal lobes (white open arrow) in a hypothyroid
patient with Hashimoto encephalopathy.

42. Radiation and Chemotherapy
 Injury may be divided into acute, early delayed injury, late delayed
injury
 Diffuse white matter injury or necrosis
 Radiation → induces cryptic vascular malformations; blood products

43. Axial FLAIR MR shows T2 hyperintense toxic demyelination (white solid arrow) in a 46 year
old woman undergoing chemotherapy for breast cancer, which will likely result in atrophy.