MDS-ES Neuropathology of Movement Disorders online course December 2020 Neuropathology of

Javier Alegre-Abarrategui MD DPhil FRCPath Consultant Neuropathologist and Clinical Lecturer, Imperial College London Director of Neuropathology, Imperial College Brain Bank Function of the cerebellum

DESCENDING SYSTEMS Upper Motor Neurons Motor Cortex BASAL GANGLIA Planning, initiating, directing Gating initiation movement CEREBELLUM Brainstem centres Sensory motor coordination Basic movements and posture

Local circuit neurons Lower motor neurons Reflex coordination

SKELETAL MUSCLE Inputs of the cerebellum Cerebral cortex

Cerebral cortex

Pons Cerebellum

Vestibular Inferior Spinal Granule cells nuclei olive cord

Purkinje cells

Pons Vestibular nuclei Inferior olive Nucleus dorsalis of Clarke Outputs of the cerebellum Cerebral cortex

Cerebellar cortex Thalamus

Deep nuclei

Dentate nuclei Vestibular Inferior Thalamus Red nuclei olive nucleus Purkinje cells

Cerebral cortex Normal cerebellum Cerebellar cortical atrophy

Climbing fibres

SCA 5, 6, 11, 26 Partially SCA8

Olivopontocerebellar atrophy (cerebellipetal atrophy) Dentatorubral atrophy (cerebellifugal atrophy)

Climbing fibres Mossy fibres DRPLA SCA3 Plus ascending FRDA tracts SC and Clarke’s FRDA also dorsal ganglia MSA, SCA 1,2,7 Olive and pons also in SCA3 Focal lesion: stroke, brain tumour, sarcoidosis Toxic: ethanol, antiepileptics, lithium, heavy metals Infectious or postinfectious cerebellitis Sporadic Endocrine Head injury Immune-mediated cerebellar (paraneoplastic or not)

Sporadic degenerative ataxias

Cerebellar ataxia MSA criteria (Neurology. 2008;71:670–676)

Idiopathic late onset (ILOCA) >50y ILOCA with cerebellar-plus syndrome No

Hereditary <50y Consider Friedreich's ataxia (FRDA)

Modified from Current Opinion in Neurology22(4):419-429, August 2009. Paraneoplastic cerebellar degeneration Underlying Antibody type Clinical picture cancer Anti-Yo Breast, gynaecological SCLC, sarcoma, Anti-Hu Encephalomyelitis neuroblastoma Limbic encephalitis Sensory neuronopathy Autonomic dysfunction Anti-Ri Opsoclonus– Neuroblastoma, breast, gynaecological Brainstem encephalitis Anti-Tr Hodgkin’s lymphoma Anti-CV2 (CMRP) Thymoma, SCLC, tumours of testis Anti-Ma Limbic encephalitis Breast Brainstem encephalitis Opsoclonus–myoclonus Anti-PCA2 Limbic encephalitis SCLC Lambert–Eaton syndrome Autonomic and motor neuropathy Episodic Pure cerebellar syndrome Dominant No Spinocerebellar ataxias (SCAs) SCA 5, 6, 11, 26

Cerebellar ataxia-plus (OPCA: SCA 1,2,7)

Consider: Ataxia with deficiency in vitamin E (AVED) - Blood smear Hereditary Abetalipoproteinaemia (ABL) cerebellar - Vitamin E Cerebrotendinous xanthomatosis (CTX) ataxia - Cholesterol Recessive FRDA Refsum's disease - Cholestanol Ataxia with oculomotor apraxia (AOA)1-2 - Phytanic acid - Alpha-fetoprotein Early onset cerebellar ataxia with retained reflexes (EOCARR) - Immunological AR spastic ataxia of Charlevoix-Saguenay (ARSACS) Mitochondrial recessive ataxia syndrome (MIRAS) Ataxia telangiectasia/ATLD SCA with axonal neuropathy (SCAN1) X-linked Mitochondrial Late-onset Tay-Sachs disease (LOTSD) Ataxic variant of ALD (AVALD) Fragile-X ataxia syndrome (FXTAS) Main episodic ataxias Episodic ataxia Phenotype Onset Triggering Mutation/locus EA1 Interictal myokymia Early childhood Physical exertion KCNA1 (12q13) Emotional stress Startle CACNA1A EA2 Interictal nystagmus Childhood or adolescence Exertion (19p13) Rarely in adulthood Stress Alcohol EA3 Episodic vertigo, tinnitus, and ataxia Linked to 1q42 No baseline deficit EA4 Episodic vertigo Late-onset Interictal nystagmus No response to acetazolamide EA6 Attacks of hemiplegia and migraine EA7 Seizures Before the age of 20 Exertion 19q13 Attacks of vertigo, weakness, and slurring Excitement Trinucleotide repeat disorders Nonpolyglutamine Polyglutamine SCA42 SCA38 SCA35 SCA28 SCA27 SCA26 SCA23 SCA19/22 SCA15/16 SCA14 SCA13 SCA11 SCA5 SCA4 SCA10 SCA8 DM1 HDL2 FRDA FRAXE FXTAS FXS SCA12 SCA17 SCA7 SCA6 SCA3/MJD SCA2 SCA1 SBMA HD DRPLA Disease CACNA1G ELOVL5 TGM6 AFG3L2 FGF14 EEF2 PDYN KCND3 ITPR1 PRKCG KCNC3 TTBK2 SPTBN2 Unknown ATXN10 ATXN8OS or OSCA DMPK JPH3 X25 or FXN AFF2 or FMR2 FMR1 FMR1 PPP2R2B TBP ATXN7 CACNA1A ATXN1 ATXN2 ATXN1 AR HTT DRPLA or ATN1 Gene Missense Missense andinframe mut Missense Missense andframeshift Missense Missense Missenses Missenses Exondels /missenses Missenses Missenses Frameshifts Inframemissense / del >800 ATTCT CTG >110 CTG >50 CTG/CAG >41 GAA >100 >200 CCG 55 CGG >230 CGG >55 CAG >47 CAG >37 CAG >20 CAG >55 CAG >32 CAG >49 CAG >38 CAG >36 CAG >49 CAG Pathogenic - 200 ------78 63 306 33 86 88 62 250 88 III III subclass I III subclass I III subclass I III subclass I III subclass I III III I II subclass I II subclass I II subclass I I subclass I II III I subclass I I subclass I I subclass I ADCA Type I subclass III subclass I III I III subclass I III subclass I OPCA OPCA OPCA III: pure III: cerebellar pigmentary maculopathyII: ataxia I: - plus nonsense missense, III:dels, Subclass splicing RNA dysfunction non II: Subclass Polyglutamine I: Subclass - codingCAG, Trinucleotide repeat disorders – general remarks

• Instability of repeat length leading to expansion in following generation : “anticipation” – particularly paternal • In polyQ disorders the repeat length inversely correlates with age of onset +/- speed of progression and clinical presentation • Only 50-80% variability in age of onset attributable to CAG repeat length: modulated by nonmutated genes for example heat shock proteins. • No correlation in the case of SCA8 Ataxia neuropathology – general remarks

• Total brain weight usually normal (except SCA with very long repeat length, DRPLA and FXTAS) • Hindbrain (cerebellum + brainstem) normally should be 11-12% of total brain weight • Degeneration is often more severe in the anterior >posterior vermis (archicerebellum) • Always sample several levels of SC and dorsal ganglia • Sample fibroblast for cultures and freeze CSF • Observe the skull in the mortuary room, as DRPLA typically thickening of the skull IHC in ataxia – general remarks

• Retraction of Purkinje cell dendritic tree - Calbindin IHC • Axonal torpedoes and empty baskets - Bielschowsky or Sevier-Munger • Grumose degeneration – SNAP25 IHC • Proteinaceaous aggregation – Ub, p62, 1C2 IHC • Morphologies: granular cytoplasmic, condensed cytoplasmic, diffuse nuclear, condensed intranuclear, axonal inclusions

PolyQ inclusions in SCA2 Images courtesy of O. Ansorge IHC in ataxia – some peculiarities

• SCA6: Large filamentous cytoplasmic aggregates do not stain with 1C2

Ub inclusions in SCA6, anterior horn

Images courtesy of O. Ansorge Control SCA6 SCA3 / MJD

OPCA

Dentatorubral

Normal cerebellum Pure cortical atrophy

Modified from Neurodegeneration: The Molecular Pathology of Dementia and Movement Disorders – with permission SCA2 SCA6 SCA3 / MJD

Cerebellar cortex Neurofilament P/non-P

Dentate nucleus Cresyl violet SNAP-25

OPCA

Modified from Neurodegeneration: The Molecular Pathology of Dementia and Movement Disorders – with permission SCA2 SCA6 SCA3 / MJD

Basis pontis

Neurofilament (non-P)

Inferior olive

Neurofilament (non-P)

Thoracic SC

MBP

Modified from Neurodegeneration: The Molecular Pathology of Dementia and Movement Disorders – with permission Pathogenesis inherited ataxias

•Loss of function

•Gain of function Protein aggregation

• Inclusion bodies are the rule in PolyQ diseases • Length of polyQ tract predict aggregation propensity and cellular toxicity in vitro • Effects may be enhanced by alteration of protein clearance, both UPS and autophagy and cause downstream mitochondrial dysfunction • Prion-like protein propagation and transfer between cells • Disconnection of inclusion formation and neurodegeneration • Purkinje cells, a main apparent disease target, usually no/minor inclusions • Distribution of aggregates does not correlate with severity of degeneration, with inclusions abundant in areas with no/minor degeneration (e.g. basis pontis in SCA3) AD SCA – shared mechanisms

• Alteration of regulation of transcription or RNA processing leading to alterations in gene expression • Direct interaction of mutant protein with promoter, repressors and splicing factors • Sequestration of splicing factors by repeat-containing (untranslated) RNA • Incorporation into polyribosomes • Alteration of transcription (remodelling of chromatin, regulators of transcription, direct mutation of transcription factors) • Alteration of synaptic transmission • Neurotransmitters (e.g. decreased glutamate reuptake) • Ionic signalling pathways (e.g. direct mutation of K+ or Ca++ channels or indirect effects) • Dysregulation of gene transcription or translation proteins necessary for regulation of ions and neurotransmitters Trinucleotide repeat disorders Nonpolyglutamine Polyglutamine SCA42 SCA38 SCA35 SCA28 SCA27 SCA26 SCA23 SCA19/22 SCA15/16 SCA14 SCA13 SCA11 SCA5 SCA4 SCA10 SCA8 DM1 HDL2 FRDA FRAXE FXTAS FXS SCA12 SCA17 SCA7 SCA6 SCA3/MJD SCA2 SCA1 SBMA HD DRPLA Disease CACNA1G ELOVL5 TGM6 AFG3L2 FGF14 EEF2 PDYN KCND3 ITPR1 PRKCG KCNC3 TTBK2 SPTBN2 Unknown ATXN10 ATXN8OS or OSCA DMPK JPH3 X25 or FXN AFF2 or FMR2 FMR1 FMR1 PPP2R2B TBP ATXN7 CACNA1A ATXN1 ATXN2 ATXN1 AR HTT DRPLA or ATN1 Gene Missense Missense andinframe mut Missense Missense andframeshift Missense Missense Missenses Missenses Exondels /missenses Missenses Missenses Frameshifts Inframemissense / del >800 ATTCT CTG >110 CTG >50 CTG/CAG >41 GAA >100 >200 CCG 55 CGG >230 CGG >55 CAG >47 CAG >37 CAG >20 CAG >55 CAG >32 CAG >49 CAG >38 CAG >36 CAG >49 CAG Pathogenic - 200 ------78 63 306 33 86 88 62 250 88 III III subclass I III subclass I III subclass I III subclass I III subclass I III III I II subclass I II subclass I II subclass I I subclass I II III I subclass I I subclass I I subclass I ADCA Type I subclass III subclass I III I III subclass I III subclass I OPCA OPCA OPCA III: pure III: cerebellar pigmentary maculopathyII: ataxia I: - plus nonsense missense, III:dels, Subclass splicing RNA dysfunction non II: Subclass Polyglutamine I: Subclass - codingCAG, Summary

• What is ataxia • Neuroanatomical circuitry involved in the function of the cerebellum • The main patterns of cerebellar degeneration • An algorithm to approach the diagnosis of cerebellar degenerations • Trinucleotide repeat disorders • Shared and specific neuropathological aspect of ataxias • Examined the neuropathology of representative examples of ataxia • Outlined the pathogenic mechanism of inherited ataxias. Thank you

23