Huntington's disease is characterized by a triad of symptoms: motor, psychiatric and cognitive. Symptoms, as well as their intensity and presentation, vary greatly from patient to patient. Clinical manifestations of the disease usually appear between the ages of 30 and 50, but the disease can be expressed at any age, from childhood or old age, before the age of 20 in 10% of cases, for example. Motor symptoms are the most visible and often the first to be identified, but cognitive or psychiatric problems may already be present. In the early stages, before the age of 20, the disease manifests itself mainly as behavioural and learning disorders.
Huntington’s disease progresses, on average, over a period of 13 to 15 years after the onset of clinical symptoms, although this figure varies greatly from patient to patient, to severe dementia, an inability to walk and swallow, and ultimately death.
Motor symptoms
The best known and most visible motor symptom is chorea. These are sudden, jerky, involuntary abnormal movements of one or more body parts. As with all involuntary movements, external factors such as stress or strong emotions can aggravate choreographic movements. Other motor symptoms include posture, walking or balance problems. Typical characteristics are a jerky gait, a grimacing face, an inability to move your eyes purposefully without blinking your eyelids or moving your head forward. Significant disturbances of chewing and swallowing are also observed in the more advanced forms. These disorders worsen as the disease progresses, to the point where people are unable to make certain movements such as dressing, washing, travelling alone, eating and even communicating, with a strong impact on their independence.
Cognitive symptoms
Cognitive impairment in Huntington's disease is multifaceted and affects executive functions in particular. Patients have difficulty thinking, planning, performing complex tasks or multiple tasks at the same time, and organizing daily activities. Disorders of language and visual perception may occur and there is often a slowing down of information processing that results in a longer reaction time to external stimulation. This cognitive decline generally leads to severe dementia in the advanced stages of the disease.
Psychiatric and behavioural disorders are prominent in Huntington's disease and often precede motor symptoms. Anxiety and depression and apathy are most common. Psychotic states with delusions (in 10% of cases), hallucinations or obsessive disorders (more than 15% of cases) may be related to schizophrenia.
Other symptoms
Other symptoms patients may experience include sleep disturbances, circadian rhythm (biological processes that occur over a 24-hour period such as sleep-wake rhythm, body temperature or hormonal production), or weight loss.
