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Spinocerebellar Ataxia Type 8 (“SCA-8”)

Spinocerebellar Ataxia Type 8 (“SCA-8”). The Cognitive and Psychiatric Profile. Lorna Torrens, Elaine Burns, Jon Stone, Mary Porteous, Adam Zeman, Helen Wright Robert Fergusson Unit, Royal Edinburgh Hospital; Western General Hospital, Edinburgh. Case History - Referral, 1998.

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Spinocerebellar Ataxia Type 8 (“SCA-8”)

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  1. Spinocerebellar Ataxia Type 8(“SCA-8”) The Cognitive and Psychiatric Profile Lorna Torrens, Elaine Burns, Jon Stone, Mary Porteous, Adam Zeman, Helen Wright Robert Fergusson Unit, Royal Edinburgh Hospital; Western General Hospital, Edinburgh

  2. Case History - Referral, 1998 • 46 year old man with 5 year history: • neurological signs • slurred speech, ataxia, impaired dexterity • cognitive decline • forgetfulness, difficulty with divided attention • personality change • labile mood, aggressive outbursts, inflexibility

  3. Case History - Examination • Mild limb ataxia • Dysarthric, slowed repetitive tongue movements • MMSE 30/30 • ‘Buoyant’ mood, poor insight

  4. Cognitive Screening • Predicted FSIQ 110 but < 20th centile on: • Stroop • Trails A and B • Verbal/Category fluency • Immediate/delayed recall of story • Rey Osterreith figure Wisconsin (‘very poor’)

  5. MRI Scan

  6. Family History • Mother, 75 years old • impulsive and inflexible from 40s • dysarthric • incongruous affect • category fluency: 6 (animals), 4 (letter) • failed Luria test (5 trials)

  7. Spinocerebellar Ataxia Type 8 (“SCA 8”) • Koob et al, Nature Genetics, 1999;21:379-384 • Family: 21 affected, 20 unaffected carriers: • SCA-8 is a risk factor for expression of condition • DNA based triplet repeat disorder (as is Huntington’s Disease) • One of an enlarging family of SCAs • Unusual - the repeat expansion is transcribed but not translated • Myotonic Dystrophy - same mechanism

  8. Reported Clinical Features of SCA-8 • Cerebellar Signs (almost all) • Upper Motor Neuron Signs (approx 50%) • Cognitive Impairments: • 26% of 68 patients covered in 11 studies (crude measures?)

  9. SCA-8:Demographics, MRI

  10. SCA 8:Neuropsychiatric symptoms

  11. Schmahmann & Sherman 1998“Cerebellar Cognitive Affective Syndrome” • 20 Cases of Diseases confined to the cerebellum resulting in impaired executive function, visuo-spatial skills and memory. Personality change including disinhibition and blunting of affect

  12. The SCA-8 expansion is associated with neurological and upper motor neuron signs. • Are there also cognitive (specifically executive) and / or affective links?

  13. The Tests • Methodology • Pre-Morbid IQ • Current FSIQ • Memory Screening • Executive Tests

  14. Executive Function Tests • COWAT – Verbal Initiation, Speed • Stroop – Speed, sustained attention, attentional switching • Hayling and Brixton – Verbal initiation, suppression, speed, rule detection and following • TEA – Visual Elevator Subtest – attentional switching, speed • (MWCST) • (BADS 6 Elements)

  15. The Results...

  16. SCA- 8: Mean Scores Controls: Mean Scores FSIQ Memory Executive Tests

  17. Average WAIS III Index Scores SCA-8 Subjects

  18. Control1 (Scores percentiles) SCA- 8 (Atrophy): CB (Scores percentiles) FSIQ Memory Executive Tests

  19. RESULTS • Significant difference in performance executive function tests (p = 0.007) • Non significant trend towards difference in performance on Visual Memory • Main discrepancies stemming from Hayling (p = 0.005) and Stroop (0.015) • Least difference in performance on Brixton

  20. PFSIQ: SCA-8 vs Controls

  21. Mean Executive Function Tests: SCA-8 vs Controls

  22. Stroop:SCA-8 vs Controls COWAT: SCA-8 vs Controls

  23. TEA: SCA-8 vs Controls Hayling: SCA-8 vs Controls Brixton: SCA-8 vs Controls

  24. ASPECTS OF EXECUTIVE FUNCTION? • Verbal Initiation/Speed - COWAT (p = 0.10), Brixton (but controls) • Inhibition of automatic responses - Accuracy vs Speed (Hayling, Stroop 71 vs 56 secs for part I) • Processing “load” ?

  25. Is there an “affective” component?

  26. BDI-II Mild Minimal HADS - Depression Normal

  27. BAI Moderate Mild Minimal HADS - Anxiety Normal

  28. Anxiety Symptoms Reported • Wobbliness in legs • Unsteady • Numbness or Trembling • Hands Shaking • Shaky

  29. Conclusions • SCA-8 linked to cognitive change: • Executive Problems • PS (not necessarily linked to motor problems) • SCA-8 may have an affective component: • Mild depression (Insufficient to account for cognitive deficits) • Anxiety (may reflect cerebellar symptoms as opposed to affective disorder)

  30. Future Thoughts • Progression • re-test in approx 2 years • Mechanisms • results from present study do not elucidate the role of the cerebellum in cognition as SCA-8 may affect other brain regions (work underway)

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