Treatment of Apathy in Huntington’s Disease and Other Movement Disorders

Apathy is one of the most prevalent neurobehavioral symptoms in Huntington’s disease (HD), occurring in approximately 70% of the symptomatic HD population. Apathy scores in patients with HD are highly correlated with duration of illness, suggesting that apathy is an inevitable consequence of advanced disease. Although less distressing than symptoms like depression and less disruptive than irritability or aggression, apathy has a considerable adverse impact on those affected with HD because it leads to a decrease of the goal-directed behaviors that contribute much to the day-to-day quality of life. As a neuropsychiatric syndrome, apathy is also common in patients with other neuropsychiatric disorders such as Parkinson’s disease, traumatic brain injury, cerebrovascular accident, dementia, and other neurodegenerative conditions. The nosologic status of apathy and lack of a clear definition has probably contributed to the paucity of therapeutic evidence in this area. Several different scales are available to measure apathy, including the Apathy Evaluation Scale, Apathy Inventory, Lilles Apathy Rating Scale, and the apathy items from the Unified HD Rating Scale, the Problem Behaviours Assessment for HD, and the Neuropsychiatric Inventory, but all are based on slightly different definitions of apathy, so the scores obtained may not be directly comparable. Assessment may also be complicated by overlap between the manifestations of apathy and other complications of HD such as depression, so the identification and treatment of these comorbid conditions is important. No adequate evidence currently supports any specific pharmacologic or psychological intervention for apathy in HD. Evidence can only be extrapolated from interventional studies done in other basal ganglia disorders such as Parkinson’s disease or other neurodegenerative disorders such as dementia. The neurobiology of apathy points towards three areas of functional connectivity: connections between the dorsolateral prefrontal cortex (PFC) and basal ganglia, orbitomedial PFC and basal ganglia, and dorsomedial PFC and basal ganglia. Pharmacologic interventions such as cholinesterase inhibitors, the dopaminergic antidepressant bupropion, amantadine, levodopa, bromocriptine, methylphenidate, and atypical antipsychotics have all been tried in other neurodegenerative disorders, but not in HD. Psychosocial interventions such as cognitive stimulation therapy and multisensory stimulation, which have been used in patients with dementia, have not been properly studied in HD. Individualized treatment should be considered, using a combination of methods, as there is no evidence to support one particular type of treatment. Multidisciplinary input, environmental modifications, improved psychosocial support, and psychoeducation programs designed to help caregivers to understand and compensate for the deficits caused by this symptom may all have a role to play in the treatment of apathy.