Determinants of functional disability in Huntington's disease: Role of cognitive and motor dysfunction

Abstract

The clinical syndrome of Huntington’s disease is notable for a triad of motor, cognitive and emotional features. All HD patients eventually become occupationally disabled; however the factors that render HD patients unable to maintain employment have not been extensively studied. This review begins by discussing the clinical triad of HD, highlighting the distinction in the motor disorder between involuntary movements such as chorea, and voluntary movement impairment, with the latter contributing more to functional disability. Cognitive disorder clearly contributes to disability, though the relative contribution compared to motor is difficult to unravel, especially since many of the tests used to asses “cognition” have a strong motor component. The role of emotional changes in disability needs more study. The literature on contributions to functional disability, driving impairment and nursing home placement is reviewed. Relevant experience is presented from the longstanding JHU HD observational study on motor vs cognitive onset, and on cognitive and motor features at the time when individuals discontinued working. Finally, we briefly review government policies in several countries on disability determination. We interpret the data from our own studies and from the literature to indicate that there is usually a close relationship between cognitive and motor dysfunction, and that it is critical to take both into consideration in determining disability.

Movement Disorder Society Task Force Viewpoint: Huntington's Disease Diagnostic Categories

“…It is increasingly clear that cognitive dysfunction is important in causing functional disability and that prominent cognitive impairment can occur with relatively less noticeable motor changes. It is less clear whether substantial cognitive impairment occurs frequently in the absence of any detectable change on motor exam . The use of a multidimensional diagnosis including the cognitive, motor, behavioral, and functional aspects of the UHDRS (question 80) resulted in a slightly earlier diagnosis of HD than when based on motor exam alone (question 17), although the difference may have reflected functional as well as cognitive changes.…”

Interrater Reliability of the Unified Huntington's Disease Rating Scale‐Total Motor Score Certification

“…Huntington's disease (HD) is an autosomal dominant, progressive neurodegenerative disorder characterized by motor disturbances, cognitive decline, psychiatric symptoms, and functional disability . It is caused by a cytosine‐adenine‐guanine (CAG) trinucleotide repeat expansion on chromosome 4 in the Huntingtin gene .…”

Fast-to-Slow Transition of Skeletal Muscle Contractile Function and Corresponding Changes in Myosin Heavy and Light Chain Formation in the R6/2 Mouse Model of Huntington’s Disease

“…Huntington’s disease (HD) is a genetic neuropathy associated with severe motoric dysfunction [1, 2]. HD is of autosomal dominant inheritance and results from an expanded cytosine-adenine-guanine triplet repeat (CAG) n in exon 1 of the IT15 gene ( HTT ) leading to an elongated polyglutamine (polyQ) stretch in the N-terminal region of the protein huntingtin (HTT).…”