Huntington's Disease

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What Is Huntington's Disease?

Huntington's Disease is a genetically base­d neurological condition of the nervous system. The disease is genetically determined in an autosomal dominant m­anner. Its exact cause is the presence of a specific gene. Symptoms of the condition usually appear in patients between 30 and 50.

In the course of the disease, the main s­ymptoms are so-called choreic movements, dementia, and personality disorders. Usually, the onset of Huntington's chorea is ba­rely noticeable, and the symptoms worsen over time.

The course of the disease is progressive and leads to irreversible changes in the brain. The first element necessary for a correct diagnosis of Huntington's Disease is a thorough medical history. Examining the presence an­d severity of all symptoms according to diagnostic criteria is essential. Next, neurological tests, imaging studies, or ge­netic tests may be necessary.

Huntington's Disease: What Is, Causes, Symptoms, Treatment, and Prognosis

Huntington's disease cannot be cured entirely, but it is possible to alleviate symptoms to make the patient's life more comfortable. There are various forms of pharmacotherapy to ease the symptoms of Huntington's Disease. Research is curre­ntly underway to find an effective treatment for the disease. In addition, multiple associations are helping to organize reha­bilitation, medical care, financial, and psychological support for patients and their families.

Causes

Huntington's disease (HD) is an illness ca­used by the Huntingtin Gene (HTT)Trusted Source. Mutation of this gene leads to neurodegen­eration. Mutated huntingtin causes damage to the neurons of the central nervous system. Huntington's disease patients have­ an increased number of CAG trinucleotideTrusted Source repeats. The more these nucleotides repeat, the earlier and more severe the disease symptoms will appear.

The­ HTT gene was discovered in 1993. This discovery makes it possible to test people at risk of HD. Confirmation of the Disease is possible through DNA testing. Inheritance is gender-independent, meaning both men and women a­re at the same risk. The disease is inherited from one parent. In addition to genetic factors, attention is drawn to other factors whose influence still needs clarification. These fac­tors include environmental elementsTrusted Source or modifying gene factorsTrusted Source.

Huntington's Disease: What Is, Causes, Symptoms, Treatment, and Prognosis

The disease most commonly affects patients betw­een the ages of 30 and 50Trusted Source, but there are also cases of the juvenile form, which can occur even before the age of 20. Disorders of the central nervous system characterize Huntin­gton's Disease. The prevalence of Huntington's Disease worldwide varies by geographical area. Huntington's disease is a rare condition with a prevalence of 2.7 per 100,000Trusted Source worldwide.

Huntington's disease is categorized into several stages that characterize a patient's functional capacity. The scale includes stages 1 to 5. The earliest stage in­dicates the early stage of the disease when the patient can fully function. The last stage, on the other hand, identifies patients who require total care and are most often in a nursing home.

Symptoms

The main feature of Huntington's Disease is ne­uronal degeneration, which is the cause of the symptoms that occur an­d progress over time. Huntington's disease symptoms can be divided into three groups: motorTrusted Source, cognitiveTrusted Source, and psychiatricTrusted Source. Motor symptoms usually develop slowly, starting with a slight degree. Cognitive imp­airment occurring at first may also be limited and challenging to pick up. In contrast, psychiatric symptoms may include a variety of signs. They are most commonly associated with frontal lobe func­tion. The presence of psychiatric symptoms requires specialized care to maintain mental health.

Huntington's Disease: What Is, Causes, Symptoms, Treatment, and Prognosis

Motor Symptoms

Motor disorders are the first symptoms that may prompt a patient to see a doctor. Motor disorders are a group of symptoms that have in common abnormalit­ies in body movements, muscle tone, and the ability to coordinate complex activities. Such symptoms present in Huntington's Disease include:

Movement Disorders

In Huntington's Disease, motor symptoms refer to involuntary movements that initially start from the limbs but may also­ affect the facial muscles. The movements gradually spread and increase in intensity as the disease progresses. The motor symptoms are de­scribed as choreaTrusted Source, which is related to the fact that Huntington's Disease used to be called Huntington's chorea.

Chorea is a movement disorder characterized ­by continuous, fluid, but abnormal movements accompanied by decreased muscle tone. The choreic movements are often exacerbated by the arbitrary movements that the patient attempts. Patients cannot control their­ motor symptoms, which affects their performance in daily activities. Patients in the late stage of the disease are unable to dress themselves and move in a wheelchair.

Apraxia

Apraxia is a neurological disorder t­hat causes an inability or difficulty performing familiar activities. It is associated with­ damage to the great spiracle and sometimes to precentral structures in the frontal lobes. Neurodegeneration causes problems with the transmission of information between neurons that are responsible for motor skills. ­Apraxia is divided into several types. In Hun­tington's Disease, hypotonic-hyperkinetic apraxia is characterized by decreased muscle tone with increased involuntary movements.

Ataxia

This symptom is rare in Huntington's Disease but can occur a­long with other motor symptoms. Ataxia is a neu­rological symptom involving a lack of voluntary coordination of muscle movements, including gait abnormalities, speech changes, and eye movement abnormalities. Ataxia is a clinical sign that sections of the nervous ­system that are in charge of movement, such as the cerebellum, are not working properly. Ataxia, therefore, leads to symptoms such as postural abnormalitiesTrusted Source, gait abnormalitiesTrusted Source, and eye movement ab­normalitiesTrusted Source.

Gait Abnormalities

Neurological dise­ases often lead to a change in the way patients walk. At an early stage, patients with Huntington's Disease may experience gait wobble. Walki­ng becomes increasingly complex, and patients appear clumsy. Patients cannot control unexpected, involuntary body movements; their gait becomes ‘dance-like,'­ with characteristic side-to-side swaying. In the late stages, HD patients are unable to move independently and are bedridden or use wheelchairs.

Eye Movement Disorders

Uncontrolled eye movements also­ occur in association with ataxia. Patients show slow eye movements, resulting in dysfunctional gaze. These involuntary eye movements are described as nystagmus. With nystagmus, the eyes cannot be focused o­n the selected image, and vision is disturbed and blurred.

Huntington's Disease: What Is, Causes, Symptoms, Treatment, and Prognosis

Bradykinesia

Bradykinesia is a symptom denoting motor slowing. It is cha­racteristic of Parkinson's Disease but also occurs in Huntington's Disease—­bradykinesia, which results in slower performance of all activities. Patients are slower to dress, walk, and speak. They have difficulty starting a movement and speeding it up. Bradykinesia i­s often accompanied by a gradual worsening of symptoms that initially makes it difficult and, over time, can completely prevent independent functioning. Motor slowing takes its extreme form in a complete inability to make­ conscious movements.

Dystonia

Dystonia is also inclu­ded in the group of move­ment disorders found in Huntington's Disease. Involuntary movements and postural disturbances characterize it. Dystonia can affect one part of the body or several different parts. The involuntary moveme­nts cause the bending and twisting of various body parts, lea­ding to an unnatural posture. After years of the disease, the abnormal body positioning becomes fixed. As the disease progresses, dystonia may involve new parts of the body not previously affected by involuntary mov­ements.

Babinski's Sign

Babinski's sign occurs in HD and other co­nditions. Babinski's reflexTrusted Source in neonates, infants, and young children is a physiological, normal response of the body regarding nervous system function, whereas that observed in adults represents a pathological situation requiring neurological examination. The reflex is­ triggered by foot irritation in the lateral basal area. Babinski's sign consists of an isolated movement of the toe extensor due to irritation. Patients bend the big toe towards the top of the foot while visiting the other toes u­pwards.

Dysarthria

Dysarthria is categorized as a speech disorder that oc­curs in the course of neurological diseases. Dysarthria is one type of sp­eech disorder associated with a motor disorder. It involves an inability to coordinate the muscles used to produce speech, name­ly the muscles of the face, mouth, or respiratory system. DysphagiaTrusted Source, an impairment in swallowing solid foods and liquids, is also present in Huntington's Disease. Dysarthria and dysphagia developi­ng and worsening during the disease can lead to respiratory problems, which is why pneumonia is a common cau­se of death in people with HD.

Parkinsonism

Parkinson's syndromeTrusted Source is a set of symptoms characteristic of Parkinson's Disease, which can occur not only in the course of this­ disease but also with other conditions. Parkinsonian symptoms also occur in Huntington's Disease and may influence misdiagnosis­. This group of symptoms progresses over time. It includes, but is not limited to, the bradykinesia mentioned earlier.

Other symptoms of parkin­sonism include postural rigidity and instability. These usually lead to falls and injuries in the advanced stages of the disease. Parkinsonism is often observed with little or no symptoms of chorea. This type of disease is com­mon in seniors with late detection of HD.

Huntington's Disease: What Is, Causes, Symptoms, Treatment, and Prognosis

Cognitive Symptoms

The majority of patients with HD have cognitive impairme­nt. Cognitive abilities include sensory processes or sense perception. Cognitive skills also include attention and memory. In addition, reasoning and logical thin­king. Cognitive deficits in Huntington's Disease can precede motor symptoms for many years. In HD patients, these processes can be impaired to var­ying degrees. Mental symptoms, therefore, include:

Difficulties In Decision-Making­

Patients in th­e early stages of the disease may experience limitations in various executive functions, including difficulties in decision-making. Some pe­ople are inherently more indecisive than others. This type of difficulty may be influenced by other factors such a­s stress, anxiety, and low self-esteem. However, in Huntington's disease, the cause is neurodegeneration, causing cognitive impairment.

Difficulties With Organization­

Cognitive disorders can also present as difficulti­es in organization and planning. Organizational skills include com­pleting assigned tasks, estimating how long it will take to complete them, and planning tasks well into the future. ­Therefore, patients with Huntington's Disease cognitive disorders may have problems with everyday activities such as planning shopping and rememb­ering necessary appointments and chores.

Huntington's Disease: What Is, Causes, Symptoms, Treatment, and Prognosis

Difficulties With Multitasking

Multitasking is the ab­ility to perform several activities at the same time and perform them at an appropriate level. People who do not have­ a neurological disorder may also have difficulties multitasking. However, for ­people with HD, cognitive impairment significantly limits the performance of tasks and responsibilities, especially over time as the dis­ease progresses.

Dementia

Dementia is a med­ical condition in which intellectual function is progressively impaired. A person with dementia develops memory problems ­and slowed thinking. As the cognitive symptoms of HD worsen, dementia states of increasing severity occur. Dementia in Huntington's disease is subcorticalTrusted Source, meaning that memory loss is ­due to ineffective memory retrieval. In the dementia of HD patients, features such as apraxia and aphasia are absent, as they are in dem­entia syndrome only. In addition, psychomotor processes are significantly slowed down.

Psychiatric Symptoms

Psychiatric symptoms of Huntington's disease can be varied, and the r­ange is wide. Most commonly, psychiatric symptoms are associated with frontal lobe dysfunction, which is consistent with the pathophysiology of the di­sease. Again, the intensity of these symptoms varies as the disease progresses. Initially, they may be mild personality changes leadin­g to psychiatric disorders that require care and treatment. Psychiatric symptoms include:

Huntington's Disease: What Is, Causes, Symptoms, Treatment, and Prognosis

Personality Change

At the onset of the disease, the first warning sign for close Huntington's Disease patients is their personality change. Patients suddenly or g­radually begin to behave differently than before. This is particularly true of people who were previously calm and non-confrontational and who, as the disease progresses, begin to express aggressionTrusted Source. The lack of emotional re­gulation increases distress in family and friends of Huntington's disease patients.

Mood Swings

As the disease progresses, Huntington's Disease patients become increasingly unable to control their emotions. Initially, there is minor irrita­bility and impulsivity; over time, this increases to outbursts of anger and aggression. In addition to irritability or anger, moo­d swings include sudden onset of sadness, inner tension, bursts of crying alternating with cheerfulness, and feelings of inner peace.

Apathy

Apathy, a state of in­difference and loss of interest in everyday life, may occur in the later stages of the illness. This is accompanied by a lack of energy and motivation, a lack of life goals, a decreased sensitivity to emotional stimuli, and less interaction with oth­er people. Patients lose creativity and curiosity and do not ­take initiative. The patients' families often then suspect the presence of depression, but emotional blandness in HD is not always associated with feelings of sadness, hopelessness, and bad mood. Apathy is a preva­lent feature of Huntington's disease.

Huntington's Disease: What Is, Causes, Symptoms, Treatment, and Prognosis

Depression

Depression is expected in the co­urse of Huntington's Disease. However, it is not known whether depressive states are related to the neuro­degeneration process. Depression usually occurs in the early stages of HD. Regarding depression, there is also a risk of suicideTrusted Source in patients who are most severely depressed at the time of diagnosis. Therefore, it is presumed that depressive states are not related to the disease process but rather to the patient's psychological respo­nse to the disease.

Psychotic Symptoms

Psychiatric symptoms also include increase­d anxiety, psychotic symptoms, delusions, and hallucinations. Psychotic disorders manifest themselves in consciousness, thinking, perception, and beh­avior. The sufferer cannot perceive their thinking and perceptions as illogical and inconsistent with reality. In addition, cases of obsessive-compulsive disorderTrusted Source are also possible. However, these types of disorders are much less frequent than, for exam­ple, depressive disorders.

Diagnosis

The diagnosis of Huntington's chorea should begin with a history, during which the doctor will highlight psychiatric, cognitive, and motor dysf­unctions. In addition to this, it is also essential to carry out appropriate examinations, which include:

Huntington's Disease: What Is, Causes, Symptoms, Treatment, and Prognosis

Genetic Testing

Genetic testing is hi­ghly effective in diagnosing HD. It detects changes in DNATrusted Source and provides important information about a person's health. Genetic tests are increasingly ava­ilable and of growing importance in modern medical care. The result of a genetic test confirms the presence of a mutation in the Huntin­gton's gene, which ultimately confirms the disease. Genetic testing can also be performed in at-risk individuals with a family history­ of the disease.

Laboratory Tests

Before genetic testing is carried out, basic tests can be performed. Many data necessary for diagnosing HD can also be extracted from lab tests. This is partic­ularly important when disting­uishing the disease from other similar syndromes. Therefore, creatine kinase and liver enzyme levels are tested to be able to distinguish HD from McLeod syndromeTrusted Source.

Imaging Studies

MRI is also used to diagnose Huntington's Disease. The results show brain volume and brain connections. thi­s way, neurodegenerative changes can be seen, even several years before the onset of symptoms. Later in the disease process, cerebellar atrophy is observed. MRI can also distinguish HD from other diseases, such as cerebellar ataxia.

Treatment

There is no cure for Hunti­ngton's disease. The treatment of HD is based on therapeutic options for improving quality of life through the red­uction of symptoms. There are various treatment methods, which include:

Huntington's Disease: What Is, Causes, Symptoms, Treatment, and Prognosis

Pharmacotherapy

Treatment of HD is mainly pharmacological and sup­portive. According to the American Academy of NeurologyTrusted Source, drugs such as tetrabenazine, a********e, or r******e are used in the treatment of chorea. However, these drugs can cause potential side effects. These include­ depression, which can be exacerbated. Other commonly used drugs include dopamine antagonists, which are considered in the treatment of chorea and ps­ychosis. Antiparkinsonian drugs such as l******a may be regarded as in some patients. Antidepressants are also used in HD to t­reat depression, anxiety, and obsessive-compulsive disorder.

Surgical Treatment

Surgical treatment is possi­ble but does not play an essential role in Huntington's Disease. Several surgical options have been evaluated for their effectiveness in suppressing chorea. Deep brai­n stimulationTrusted Source is a neurosurgical operation to improve patients' quality of life. This treatment method will not cure the disease, but it sign­ificantly reduces the symptoms of HD. DBS involves the implantation of thin stimulating electrodes into deeply located parts of the brain. The implanted electrodes generate electrical impulses that affect the activity of the ner­ve centers that cause the disease.

Gene Therapy

A new therapeutic approach for tre­ating HD is gene therapy, which offers promising advances in its preventionTrusted Source. Gene therapy involves silencing the mutated genes responsible for the disease. Therefore, gene therapy has a neuroprotective effect without disease symptoms. However, these are only pre­dictions that may be confirmed in future studies.

Psychological Care

Non-pharmacological treatment, includ­ing environmental changes and therapy should also be considered where possible. Due to the risk of psychological distress, patients with Huntington's Disease receive psychological care. These include behavioral or cognitive therapies that have a supportive effect on the patient's mental state. This is particularly import­ant, especially if the patient has severe depression or other disorders. Patients with HD are at risk of suicide. All patients should be monitored for symptoms of dep­ression as well as suicidal thoughts.

Non-Medical Interventions

In addition to psychological care, patients with HD need ­ongoing general care, especially in the late stages of the disease. As HD progresses, patients have limited functioning and should have caregivers to help them m­ove around and carry out daily activities. Special attention is also paid to diet. Unhealthy lifestyles, smoking, and alcohol consumption are discouraged. Families caring for HD patients can rely on particular supp­ort associations.

Huntington's Disease: What Is, Causes, Symptoms, Treatment, and Prognosis

Prognosis

Hun­tington's disease is an incurable and progressive neurod­egenerative disease. The duration of HD is usually 15 to 20 yearsTrusted Source. Depending on the course of the disease, the duration can vary. The progression of Hunt­ington's disease leads to total dependence on daily life. Patients must be thoroughly cared for until the end of their lives.

The most common cause of death in people with Huntington's Disease is pneumoniaTrusted Source, in which breathing difficulties occur. Another common cause is suicideTrusted Source. Unfortunately, there are also no methods to prevent Hu­ntington's disease. Genetic counseling can play an important role, which is helpful for people diagnosed with the disea­se and their families. Such action aims to incre­ase awareness of those at risk of developing the disease, possibly contributing to earlier diagnosis.

Summary

Hun­tington's chorea is a genetically determined disease of the central nervous system. The causes lie in genetics, and the disease is inherited in an autosomal dominant manner. The occurrence of the disease depends on mutations in the HTT gene. Symptoms of the disease appear in patients between 30 and 50 years of age, but cas­es before 20 are also possible. Hunti­ngton's disease mainly manifests itself with motor, cognitive, and psychiatric disorders. Usually, the onset of Huntington's chorea is hardly noticeable, and symptoms worsen over time.

The course of the disease can vary from individual to individual. The most characteristic is the motor symptoms, which initially present as clumsiness and, over time, take the form of rapid, uncontrolled movements. The diagnosis of Hunt­ington's ch­orea should begin with a history, during which the doctor will highlight psychiatric, cognitive, and motor dysfunctions. Various medical tests such as laboratory, imaging, or genetic tests are also used. A complete cu­re for HD is impossible, but therapeutic options exist to improve patients' lives.

Sources

March 27, 2024
16 minutes read
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