SHORT REPORT

Motor overflow in Huntington’s disease

N Georgiou-Karistianis¹, K E Hoy¹, J L Bradshaw¹, M Farrow¹, E Chiu², A Churchyard³, P B Fitzgerald⁴ and C A Armatas⁵

¹ Experimental Neuropsychology Research Unit, Psychology Department, School of Psychology, Psychiatry & Psychological Medicine, Faculty of Medicine, Nursing and Health Sciences. Monash University, Victoria, Australia
² Department of Psychiatry, University of Melbourne, Parkville, Victoria, Australia, and Aged Psychiatry, Education and Research, St George’s Health Service, Kew, Victoria, Australia
³ Department of Neurology, Monash Medical Centre, Clayton, Victoria, Australia
⁴ Alfred Psychiatry Research Centre, The Alfred and Monash University, Department of Psychological Medicine, Faculty of Medicine, Nursing and Health Sciences, Monash University, Victoria, Australia
⁵ School of Psychology, Deakin University, Geelong, Victoria, Australia

Correspondence to:
Correspondence to:
Dr Nellie Georgiou-Karistianis
Department of Psychology, Monash University, Clayton 3800, Victoria, Australia; nellie.georgiou-karistianis{at}med.monash.edu.au

We investigated both motor overflow and ability to control voluntary movement in patients with Huntington’s disease (HD). We hypothesised that, compared with controls, overflow would be significantly greater in HD participants and that they would exhibit poorer control of voluntary movement. In a finger flexion task, participants had to maintain target forces representing 25, 50, or 75% of the maximum strength capacity for whichever finger was performing the task; overflow was measured in the corresponding finger of the non-responding hand. HD participants exhibited significantly greater motor overflow than controls, and more difficulty controlling the target force with the active hand. In addition, the degree of overflow in HD participants positively correlated with overall UHDRS motor symptom severity.The presence of exacerbated motor overflow in HD, and its correlation with symptom severity, is an important finding worthy of further investigation.

Keywords: motor overflow; Huntington’s disease; force

Abbreviations: LVDT, linear variable differential transformer; MADRS, Montgomery and Asberg Depression Rating Scale; MMSE, Mental State Examination; NART, National Adult Reading Test; UHDRS, Unified Huntington’s Disease Rating Scale

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