Early-Motor Phenotype Relates to Neuropsychiatric and Cognitive Disorders in Huntington's Disease

To determine the relationships between the motor phenotype and the presence of specific neuropsychiatric and neuropsychological disorders in patients with early motor-manifest Huntington's disease (HD).

From the Enroll-HD study, 3,505 individuals with HD who had ≤5 years of motor symptoms were classified based on the predefined parkinsonism/chorea index into chorea-dominant (n = 1125), parkinsonism-dominant (n = 867), and mixed-motor phenotype (n = 1513) groups. An analysis was performed on the results of the short Problem Behaviors Assessment. This test assesses patients for neuropsychiatric disorders such as depression, irritability/aggression, apathy, obsessive-compulsive behaviors, and psychosis as well as cognitive disorders by using neuropsychological tests such as the Stroop Interference test, Trail Making Test Part A and B, letter fluency, Symbol Digit Modality test, and animal fluency test.

In these early motor-manifest HD individuals, motor phenotype was associated with neuropsychiatric and cognitive changes. Independent of the age of motor onset, motor duration and severity, CAG repeat expansion, and medication use, the parkinsonism-dominant group had more severe neuropsychiatric disorders (depression, apathy, obsessive-compulsive behaviors, and psychosis) and poorer performance on all cognitive tests than those patients in the mixed-motor phenotype and chorea-dominant groups. The patients in the chorea-dominant group had less apathy and depression than those in the mixed-motor phenotype group.

In the early stage of motor-manifest HD, parkinsonism-dominant patients appear to have more severe neuropsychiatric disturbances and more cognitive impairments than those HD patients with chorea-dominant and mixed-motor phenotypes. Future studies should explore the brain mechanisms of these disorders and the possible treatments. © 2020 International Parkinson and Movement Disorder Society.