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
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