Huntington's disease is a genetic neurodegenerative disorder that causes motor and cognitive decline. While it is known for disrupting motor skills, it also significantly impacts cognitive abilities and can cause dementia. There are two types of Huntington's disease-associated dementia - cortical and subcortical. Subcortical dementia affects areas below the cortex and leads to motor impairments, while cortical dementia impacts functions like memory, language, and perception. Cognitive testing can help diagnose dementia early to allow for mental stimulation activities that may help slow progression. Currently there are no treatments to stop or cure cognitive decline from Huntington's disease.

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Dementia in Huntington’s Disease
Bridget Pody
Gwynedd Mercy University
PSY209-Dementia: Awareness, Understanding, and BP
Kaitlin M. Reilly

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Dementia in Huntington’s Disease
Abstract: Huntington’s disease (HD) is a progressive neurodegenerative disease that slowly
disrupts the function of motor skills in its victims. It is not commonly noted, but the disease also
has a large effect on the person’s cognitive abilities. Patients with HD have a higher risk of
dementia due to the disruption of the neurons and their connections in the brain. There are two
types of dementia that effect different areas of the brain. Thus, the patient is also affected
differently. These patients are now being introduced to tests used to diagnose dementia and
Alzheimer’s disease to measure for possible decline in cognitive abilities.
Huntington’s disease is a rare, yet devastating and impactful disease amongst its victims.
It is a fatal genetic disorder that disrupts the nerve cells, known as neurons, in the brain. These
cells begin to breakdown and slowly cause muscular weakness, atrophy and they will eventually
begin to disrupt several mental and cognitive abilities. The disease appears to be the most
common in people between the ages of 30 to 50 years old. The average life expectancy of most
victims is 10-25 years from the start of the first symptoms of the disease.
The prevalence of Huntington’s disease is about 10 in 100,000. That is approximately
30,000 cases in the United States alone. In Huntington’s disease (HD), the victim has an
excessive amount of CAG, which produces what is known as a huntingtin protein. Genetic
studies and analyses have found abnormalities in chromosome four, alongside repetition of
certain genetic material. The huntingtin protein contains glutamine blocks and develops a shape
different from a normal protein. This causes abnormal behaviors within the protein, thus causing
neurons and other cells in the brain to malfunction and die. The loss of the neurons occurs

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mainly in the caudate nucleus and putamen within the striatum. Degeneration is also caused by
chemical changes in the neurotransmitters. Substances such as glutamic acid and acetylcholine
are reduced, while lactate appears to be elevated.
The most common misconception with Huntington’s disease (HD) is its impact solely on
the neuromuscular system. While HD is most well-known for this factor, several people are not
aware that it can also have a large psychological effect on the patient. The hallmark and the most
common symptoms are those that are rather similar to several other degenerative diseases. Thus,
it can be easily mistaken for more well-known diseases including Parkinson’s disease,
Alzheimer’s, and amyotrophic lateral sclerosis (ALS). These hallmark symptoms of HD include
involuntary muscle movements and contractions (chorea) and slurred speech. Psychological
symptoms include forgetfulness, impaired judgment, personality changes, and depression, found
commonly in dementia or Alzheimer’s disease. Regarding these psychological symptoms, it is
possible for patients with HD to be diagnosed with what is known as, Huntington’s disease
associated dementia.
Dementia in Huntington’s disease appears the same way as every other type of dementia,
regarding the effects on memory, recall, recognition, and other common findings in dementia.
However, this form of dementia features more psychological impacts than other types. While HD
is well-known for the degeneration of motor skills, there also appears to be a significant amount
of cognitive decline. As a matter of fact, cognitive decline has been found to onset before the
main symptoms even begin to appear.
In order to take early action, it is important for the patient to undergo neuropsychological
analysis and be able to identify the amount of decline and what functions appear to have a higher
deficit. The most common test for a patient to undergo in the diagnosis of dementia is the Mini-

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Mental State Examination (MMSE). However, there are still numerous tests that can be
performed to measure the further rates of cognitive decline. As compared to MMSE, other tests
require the use of numerous mental tasks that also force the different areas of the brain to work
harder than usual. This makes it more challenging for the patient, thus making it easier for
physicians to determine which parts of the brain are being most impacted by the disease. Other
tests in the diagnosis of dementia can also measure how the disease affects deductive reasoning,
visual perception, long term verbal memory, attention/concentration, word searching, and
categorization abilities. These include physical examination, including medical history. Other
common tests include MRI and PET scan on the brain and spine, CSF analysis, liver and kidney
tests, and EEG’s. During these tests, results of performances and results are compared to normal
results found in their age criteria.
The progression of HD associated dementia also highly depends on the rate of
degeneration of the disease itself. The dementia can be either slowly or rapidly progressive.
Slower progression is the nerve cells in the brain losing their function over the course of several
years. Rapid progression features a sudden advancement of the condition. More neurons in the
brain continue to die faster. This can eventually lead to brain shrinkage, also known as cerebral
atrophy. Memory loss and cognitive impairment tend to be a greater risk in Huntington’s disease
patients than any form of dementia not associated with the disease. The symptoms of dementia
begin to worsen due to the victim’s decline in mental and emotional health.
It should also be important to note that HD also causes psychiatric disturbances,
especially at the onset of cognitive decline. It has been shown that patients with Huntington’s
disease are at a higher risk for anxiety, depression, and other disturbances such as judgment and,
sometimes, symptoms mirroring schizophrenia. The risk of depression and anxiety is higher as

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the patient slowly begins to lose their motor and cognitive abilities. The prevalence is
approximately 40 to 70 percent of HD patients in all disease stages. Mania is found in 2 to 10
percent and suicide can be found in nearly 6 percent of cases. Dementia can be detected in all
stages, but the mean age of onset is approximately 40 years old, which is almost two thirds of a
difference in non-associated dementia.
The rates of dementia in HD are increasing. There are two types that can affect the
patient differently. These categories include cortical and subcortical. The classification of
dementia is dependent on the areas in which degeneration begins to occur. Subcortical is the
most common and most impacting, affecting the thalamus, cerebellum, hypothalamus, and brain
stem. When these sections are impacted, motor impairments, mainly chorea, begin to appear.
Meanwhile, cortical dementia only appears to affect the cerebral cortex. This section is
associated with the result of several impairments such as aphasia, agnosia, apraxia, amnesia, and
comprehension. The striatum has been found to be the most affected area in patients with HD.
The purpose of this area is sequencing and procedure learning.
In Huntington’s disease dementia, the memory classification that is most effected is
declarative, which includes episodic and semantic memories. Episodic memory is responsible for
recall, while semantic is in charge of categorizing factors from previous experiences. Short term
memory appears to be more effected than long term memory. HD patients also experience
impaired learning of motor skills. For example, some patients experience impairments in
learning, which may be a result of decline in eye movement, but mostly in late stages of the
disease. As degeneration continues to progress throughout the brain, beginning in the core,
communication skills are eventually lost. The skills that are most commonly affected are
speaking clearly, starting conversations, organizing words, and understanding what they are

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trying to say. Assessments to measure attention and concentration appeared to be only
moderately impaired, compared to cognition. The patient may present cooperation, but may not
necessarily show interest in the activity. Language skills are also impaired, but mainly only in
the final stages of the disease.
The cognitive declines presented in Huntington’s disease dementia are caused by the
damage of neurons and connections throughout the sections of the brain. Unfortunately, these
effects are irreversible for the time being. While there is no current treatment or cure for these
effects, acetylcholinesterase inhibitors can affect cognitive abilities as the victim’s condition
worsens. Antipsychotic and anti-anxiety medications can diminish the severity of the
psychological symptoms. Therapy also contributes to assisting a patient as their disease worsens.
Group therapy and support groups are often suggested, especially with several patients being at
an increased risk of depression and suicidal thoughts. It is important for the overall disease to be
managed so that the progression of the dementia might decrease. Researchers are currently
researching the brain’s capabilities of forming new neurons. They are also continuing to measure
the formation of new connections in the neurons, which can be associated with improvement of
cognition.
When a person contains the gene linked to Huntington’s disease, they will eventually face
it at some point in their life. The onset of the disease can occur at any point of life, most
commonly in ages greater than 30 years. Maintaining a healthy lifestyle with diet and exercise is
important to slightly ease the symptoms when the disease onsets. Victims at high risk of HD can
participate in mental stimulation activities. Some of these include reading, writing, solving
puzzles, listening to music, and learning new skills.

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In conclusion, Huntington’s disease has been studied for years since its discovery in the
late 1800’s. Victims of the disease find that they show impairment in their motor skills.
However, it is not typically reported enough that HD can also greatly affect the patient
cognitively. This form of dementia has been found in several HD patients over the years,
regardless of the age group or disease stage. The key is early diagnosis, which includes a wide
variety of tests involving physical and cognitive demands. Early diagnosis helps, so that patients
might still be able to participate in several activities that promote mental stimulation. HD
associated dementia is often a result of the constant degeneration of the nerve cells within the
brain. This explains why victims are also at an increased risk of several mental abnormalities,
such as depression and anxiety. There is currently no cure, treatment, or specific methods of
preventing the disease. However, there are several drugs on the market that will lessen the
severity of symptoms featured in most patients. Alongside, improving several different lifestyle
behaviors is important in those that contain the gene that will cause the victim to develop the
disease at some point later in life.

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References:
Bezdicek, O. (2013). Validity of the Montreal Cognitive Assessment in the detection of cognitive
dysfunction in Huntington’s disease. Applied Neuropsychology, 20(1), 33-40. Retrieved
November 8, 2015 from EBSCOhost database.
Heindel, W. C., Butters, N., Salmon, D. P. (1988). Impaired learning of a motor skill in patients
with Huntington’s disease. Behavioral Neuroscience, 102(1), 141-147. Retrieved
November 8, 2015 from EBSCOhost database.
Hindley, N. (1996). Late onset Huntington’s disease as a cause of dementia. Where should the
clinician’s index of suspicion lie?, International Journal of Geriatric Psychiatry, 11(8),
729-733. Retrieved November 6, 2015 from EBSCOhost database.
Sampaio, C., Borowsky, B. (2015). Cognitive impairment and dementia (mild or major
neurocognitive disorder) in Huntington’s disease. Neuropsychiatric symptoms of
movment disorders, 211-222. Retrieved November 8, 2015 from EBSCOhost database.
Vuono, R. (2015). The role of tau in the pathological process and clinical expression of
Huntington’s disease. Brain: A Journal of Neurology, 138(7), 1907-1918. Retrieved
November 8, 2015 from EBSCOhost database.
Zakzanis, K. K. (1998). The subcortical dementia of Huntington’s disease. Journal of Clinical
and Experimental Neuropsychology, 20(4), 565-578. Retrieved November 6, 2015 from
EBSCOhost database.