Measuring the functional impact of cognitive impairment in Huntington’s disease

BACKGROUND: Patients with Huntington's disease (HD) exhibit a variable predominance of cognitive, behavioral and motor symptoms. A specific instrument focusing on the impact of cognitive impairment in HD over functional capacity is lacking. OBJECTIVE: To address the need for a brief and specifically developed HD questionnaire able to capture functional aspects suspected to be sensitive to cognitive impairment. METHODS: We developed and validated the "Huntington's Disease-Cognitive Functional Rating Scale" (HD-CFRS) in 78 symptomatic carriers of the Huntington's disease mutation. We also administered the HD-CFRS to a knowledgeable informant to measure the level of agreement. To explore the association between HD-CFRS scores and participants' cognitive status, we administered objective measures of cognition. Participants were classified as cognitively preserved (HD-NC), as having mild cognitive impairment (HD-MCI), or as having dementia (HD-Dem). RESULTS: The HD-CFRS showed concurrent validity and internal consistency in the three groups. HD carriers and informants in the HD-NC group obtained similar HD-CFRS scores. However, in patients with mild cognitive impairment and dementia, informers reported greater functional impairment than HD participants. The HD-CFRS total score showed strong correlations with measures assessing cognition. CONCLUSIONS: These findings support the utility of the HD-CFRS as a brief and reliable instrument to measure functional defects associated with cognitive impairment in HD. We believe this questionnaire could be a useful tool both for clinical practice and research.