"Frontal" behaviors before the diagnosis of Huntington's disease and their relationship to markers of disease progression: evidence of early lack of awareness

Abstract

Huntington's disease has been linked with fronto-subcortical neuropathology and behaviors consistent with this dysfunction. Little is known about these "frontal" behaviors in the earliest phase of the illness. Comparisons between participants in the Predict-HD study (745 "expansion-positive" and 163 "expansion-negative" control subjects) on the Frontal System Behavior Scale looked for evidence of frontal behaviors, including apathy, disinhibition, and executive dysfunction. The authors were also able to compare participant and companion reporting of these frontal behaviors as a possible indication of awareness of behaviors. Expansion-positive individuals reported significantly more of these frontal behaviors than expansion-negative peers. Self- and companion-reported frontal behaviors were related to other Huntington's disease markers. Expansion-positive participants closest to Huntington's disease diagnosis showed greater discrepancies with companions on ratings of frontal behaviors. Even though most are more than 10 years from Huntington's disease diagnosis, mild frontal behaviors were present in this prediagnosed sample, which might make these behaviors useful as markers for Huntington's disease onset. Participant/companion discrepancies, especially closest to Huntington's disease diagnosis, might suggest early lack of awareness in these individuals.

Figure 1

Relationship between probability of diagnosis within 5 years and FrSBe Total score for participants Note. y-axis = FrSBe Total score rated by participants, with higher score indicating more “frontal” behaviors. x-axis = probability of HD diagnosis within next 5 years based on Langbehn et al. (2004). Solid line represents regression line and dotted lines represent 95% confidence intervals.

Figure 2

Relationship between probability of diagnosis within 5 years and FrSBe Total score for companions Note. y-axis = FrSBe Total score as rated by companions, with higher score indicating more “frontal” behaviors. x-axis = probability of HD diagnosis within the next 5 years based on Langbehn et al. (2004). Solid line represents regression line and dotted lines represent 95% confidence intervals.

Figure 3

Relationship between probability of diagnosis within 5 years and FrSBe Total difference score (participant score - companion score) Note. y-axis = difference score for FrSBe Total score (participant score - companion score), with higher score indicating participant is rating more “frontal” behaviors and lower score indicating companion is rating more “frontal” behaviors. x-axis = probability of HD diagnosis within the next 5 years based on Langbehn et al. (2004). Solid line represents regression line and dotted lines represent 95% confidence intervals.