Comparisons
Part 3

A comparison of HD to Alzheimer's and Parkinson's diseases

Neurobiology: Emotional/Cognitive Comparisons

Disclaimer: Despite many similarities, these cognitive and emotional signs present at different stages of the disease in different people. A person with HD may very well maintain healthy cognitive functioning throughout the remainder of his/her life.

The symptoms of Huntington’s disease are both behavioral and cognitive. Symptoms are the direct result of neurological changes in the brain. Apathy is one of the most common behavioral symptoms of HD due the death of nerve cells controlling “emotions” in the brain. Deterioration of a certain area of the brain called the caudate nucleus causes HD sufferers to be unable to control intensities of emotion, and makes them more likely to experience frustration, irritability, and aggression. For more on behavioral symptoms associated with HD go here here.

In addition to behavior symptoms associated with HD, many cognitive changes also arise with the onset of Huntington’s disease due to neuronal damage. A patient’s ability to initiate a conversation and to communicate is altered due to degeneration in the brain. Furthermore, an individual suffering from the cognitive symptoms of HD may have memory, problem solving, and judgment difficulties. Tasks that were once simple are difficult for an HD patient to perform efficiently. An HD patient also experiences difficulty with visual spatial impairment, awareness, and organization. For more on the cognitive symptoms associated with HD, go here.

Similarly, patients of Alzheimer’s disease may experience both behavioral and cognitive changes at different stages of their disease process, many which are similar to HD. Difficulty with the acquisition of new information is generally the most salient symptom to emerge in patients with AD. Whereas learning new information for HD patients is disorganized and slow, Alzheimer’s patients experience rapid forgetfulness and an inability to store information. Several studies have demonstrated that people with AD lose more information over a brief delay than other patients with disorders that involve amnesia or dementia. Though at first their symptoms may be mild, people in the later stages of AD may forget how to perform simple tasks, like brushing their teeth or combing their hair. They neglect to bathe, or wear the same clothes over and over again while insisting that they have taken a bath or that their clothes are still clean. They can become lost on their own street, forget where they are and how they got there, and not know how to get back home. Eventually, patients need total care because they are unable to think clearly and perform tasks for daily living.

Another similarity to HD is that Alzheimer’s patients lose their initiative to perform normal activities or to engage in activities they used to enjoy. They often become very passive, sitting in front of the television for hours and sleeping more than usual. Furthermore, Alzheimer’s patients can experience rapid mood swings for no apparent reason, and their personality can vary from becoming extremely confused and suspicious to being fearful or dependent on a family member. They also may see, hear, smell, or taste things that are not there. Finally, like those with HD, Alzheimer’s patients sometimes exhibit poor judgment, which creates safety issues when left alone. They may wander and risk exposure, accidental poisoning, falls, self-neglect, or exploitation.

For patients with Parkinson’s disease, the most prominent symptom is tremor. Tremor often starts in one extremity and worsens with precipitating factors such as stress, fatigue, and cold weather. The tremor associated with PD occurs predominantly at rest, and results in the slowness of a patient’s movement (also known as Bradykinesia) A delay in initiating movements develops due to the brain’s inability to transmit necessary instructions to the body at a normal rate. Parkinson’s patients often report difficulties in performing activities of daily life, such as dressing, walking, and doing household chores. Symptoms that appear later in the progression of the disease include poor balance and the inability to swallow. Upon walking, a Parkinson sufferer has a decreased or non-existent arm swing, short shuffling, and difficulty negotiating turns. Another major symptom is rigidity, characterized by increased tone and stiffness in the muscles; rigidity is responsible for a Parkinson patient’s sometimes mask-like facial expressions and stooped posture.

As with HD and AD, depression is commonly seen in the early stages of Parkinson’s disease. It is estimated that about half of people with Parkinson’s may suffer from depression. This is thought to be not only a reaction to the diagnosis, but rather an intrinsic part of the disease process. Also, as with HD, Parkinson’s disease causes anxiety and can cause panic attacks. Symptoms of anxiety include breathlessness, sweating, chest discomfort, choking, and dizziness. In severe cases, patients may have feelings such as the fear of dying or the fear of going insane. Also, about 15-25% of individuals with Parkinson’s disease will suffer from memory and cognitive deficits similar to those of Huntington’s disease patients. Mild cognitive deficits are common in Parkinson’s and are characterized by a lack of flexibility in thought, difficulty in learning new information, and impaired visual-spatial skills. Short-term memory deficits are common and may progress to more severe memory deficits. Language skills are relatively spared although some studies have found a mild impairment in naming. Higher executive function (abstract thinking, planning abilities, judgment, and initiative) is often affected in patients with Parkinson’s disease as well.

Last Modified: 5-20-04

An educational product of HOPES, not to be used in place of medical care. For more information about HOPES, click on the Logo. To contact HOPES with comments or questions, click here.