6) Higher Cortical Function
Research has indicated the persons with HD commonly experience memory disorders, and that these disorders are apparent prior to the emergence of motor dysfunction. This has been found to be the case with our population. Memory dysfunction is often severe enough to cause significant problems with work and family routines, even in the early stages. As the disease progresses, further deterioration is likely to occur.
Memory dysfunction commonly takes the form of:
Poor retrieval and word-finding difficulties.
Poor encoding (inability to process several pieces of information at once.
Poor short-term memory
Long-term memory usually stays relatively intact, although toward the latter stages of the disease this may be affected.
7) Behavioural Components
Reduction of concentration span and an impairment of cognitive and organisational skills are some of the first obvious symptoms to occur, and again, cause difficulties in the family and workplace.
Body image (ability to perceive the location and relationship of body parts) usually remains intact until well on in the disease process. If dyspraxis develops, then it is likely that body image will also be affected.
Dyspraxis is the inability to carry out unfamiliar motor tasks, even though the means to do it remain intact. It may be seen in HD persons who are able to automatically carry out an action, but are unable to do so on command (e.g., the person may be fully mobile but is unable to walk sideways on command or even on demonstration.
Spatial Orientation (form and space perception)
Dysfunction is apparent in patients who are, for example, unable to distinguish front from back, or the inside of a sweater. This problem with body image and spatial confusion makes dressing difficult, and misinterpretation of facial relationships makes eating a major problem. Also, it may be that a patient who has reasonably good motor control displays very poor ability to judge the amount of space required to fit through a gap (e.g., a doorway) or to reach or negotiate an object (e.g., sitting down in a char). The patient loses contact with his/her environment, internal state, posture and movement. In other words, there is a malfunction of the interaction between sensory input, neurological interpretation and appropriate behavioural responses.
Generally this is seen in the latter stages of HD, but there may be subtle indications of it early on in the disease process.
8) Hand Function
Understandably, a common complaint amongst persons with HD is depression. Even if not manifest as psychotic depression, persistent feelings of despair, low energy, poor motivation, lack of alertness and general low spirits can severely affect the individual’s ability to cope with, and respond to, therapy.
Some individuals in advanced stages of the disease suffer a breakdown in the internal mechanism concerned with regulating emotional expression. Personalities do not change as such, but there is less control over personality traits. "Difficult" personalities become even less controlled and this can cause significant patient management problems.
In the more advanced stages, the ability to relate effectively with others in terms of appropriatness and awareness of social norms may become disrupted (e.g., overstepping personal space boundaries or failure to make eye contact).
Generally the HD process does not affect the range of movement of the hand, but the ability to coordinate finger movement or regulate grip strength is affected. Thus, hand dexterity and manipulative skills decrease. Fine motor skills deteriorate first, and this may be evident fairly early on in the disease. Gross hand skills may remain relatively unimpaired, but if involuntary movement becomes severe then hand function also suffers.
9) Visual Disorder
There are instances where persons in the advanced stages of HD have developed a ‘tonic grasp’. That is, where the hand is constantly held in a clenched position. Initially some voluntary release of the grasp is usually possible, but over time contractures may form and the hand becomes ‘set’.
Eye movement controls usually unaffected in the early stages. Latter-stage persons may be unable to smoothly follow an object travelling across the visual field, or may find it difficult to rapidly focus on an object. Controlled eye movements, independent of neck movements, may also be lost.
10) Exercise Tolerance
Poor exercise tolerance due to factors such as decreased respiratory capacity, inactivity muscle weakness and dysfunction of normal movement is evident at all stages of the disease.