Introduction
Huntington’s disease (HD) is an inheritable and neurodegenerative disease. It is characterized by progressive psychiatric, cognitive, and motor symptoms. It is significant to familiarize with the phenotypes since patients can present with one or more symptoms of the disease. Loss of balance and chorea are the first symptoms recognized by the patients. However, the families always notice personality or cognitive changes before first symptoms. The disease is most common in races from northern Europe. This paper is set to discuss the etiology and risk factors, pathophysiological processes, clinical manifestations, complications, as well as diagnosis of Huntington’s disease.
Etiology and Risk Factors
A defective gene located on chromosome four causes HD. Children of parents with Huntington’s disease have a fifty percent chance of developing the disease since it is hereditary (Bates, Tabrizi, & Jones, 2014). Huntingtin is a protein produced by the HD gene and it is found in almost all body tissues. However, its concentration in the brain is higher as compared to other body parts. The function of the protein is yet to be known, but its defective form causes HD. Huntington’s disease causes deterioration in brain neurons. The most affected parts of the brain include the cortex and the basal ganglia. The whole basal ganglia including the caudate and the putamen are also affected. The HD typically affects both the cognitive and physical functioning. The main function of the cortex is to control the cognitive functions of the brain. Such functions include understanding and high-level thinking. Basal ganglia help in the performance of smooth movements. Anything that affects it has an equal effect on movement and stability (Rüb, Vonsattel, Heinsen, & Korf, 2015).
Clinical Manifestations and Complications
The rate of progression of the disease, as well as the onset of symptoms, differs from one patient to the other. However, in most cases, the symptoms begin after an individual has attained 30 years of age. The symptoms progress slowly for 10 to 25 years. Early symptoms of the disease often include a few changes in the cognitive system. There may also be slight changes in movement and posture. The individual may find it hard to stand upright or maintain a given posture. As the disease progression continues, individuals with HD usually experience personality changes such as mood swings, depression, as well as irritation. Such a person may also experience troubles with concentration, memory, decision-making, and learning new things. Another common feature of HD is an Obsessive-compulsive disorder (OCD). This makes the individuals repeat the same activity (Guillory & Carasco, 2013).
After the onset of the initial symptoms, they develop gradually into more pronounced states. Such pronounced symptoms include involuntary twitching of the neck, head, as well as jerking of the legs or arms. Symptoms developed in the later stages of Huntington’s disease include difficulty in swallowing and eating, poor concentration, and difficulty in movements. This is due to the death of brain cells that control thinking, understanding, as well as movement. These motor symptoms can be divided into two; impaired voluntary movements (IIM) and voluntary movements (VM). These cause poor coordination in the limbs as well as the neck.
When the postural reflexes are lost, the symptoms worsen. They follow a pattern where others decline while some get worse. For instance, chorea declines while bradikinesia, rigidity, and dystonia become more marked (Guillory & Carasco, 2013). In early stages of cognitive symptoms, individuals report multi-tasking difficulties, short memory, and concentration. The style of thinking becomes less efficient and more concrete. The organization, timing, initiation, and planning of thought processes become slower as well as disorganized over time. Depression occurs in almost all HD patients as the disease progresses. Other psychiatric disorders are psychosis and obsessive-compulsive disorder. Early diagnosis of these psychiatric disorders is essential to ensure proper treatment is started.
Pathophysiological Processes
Neuropathology in Huntington's disease occurs when there is gross atrophy of putamen and caudate nucleus within the neostriatum. This atrophy is accompanied by astrogliosis and selective loss of neurons. Prominent loss of neurons can also be seen within the cerebral cortex layers. Other regions showing atrophy, but in varying degrees, include subthalamic nucleus, cerebellum, globus pallidus, and subsantia nigra. Pathologic grade determines the degree of atrophy in the affected regions. The severity of Huntington's disease pathology is graded depending on neuronal loss, gliosis, as well as striatal pathology. In grade 0 and 1 of HD, gross striatal atrophy (GSA) is not observed. Grade 0 does not have any histologic pathology that can be detected in the presence of a positive history of HD in the family line and an ideal clinical picture (Rüb, Vonsattel, Heinsen, & Korf, 2015).
Neuropathologic changes in grade one are detectable under high-resolution microscopes. These do not show any sign of atrophy. In grade 2, the convex nature of caudate nucleus remains unchanged, and striatal atrophy can be easily observed. Striatal atrophy in grade three becomes more severe while the caudate nucleus changes from convex to flat. In grade four, the severity of striatal atrophy increases while the caudate nucleus becomes concave. Loss of neurons and striatal atrophy has been studied extensively. However, attention on the structure and functioning of the neurons that survive has been very little. The investigations carried on these surviving neurons show regenerative changes (Guillory & Carasco, 2013). In comparison to neurons from normal brain cells, HD neurons have greater density, large dendritic spines, and more dendrites, with greater somatic areas. For one to completely understand Huntington’s disease, an explanation on the causes of these regenerative changes is required.
Diagnostics
When specific symptoms associated with Huntington’s disease appear on an individual, a diagnosis of HD can be suspected. Most of these symptoms occur beyond 30 years of age. The first step in the diagnosis of HD is carrying out a comprehensive physical examination to find out whether the disease process has started. A physician should assess signs of involuntary movements of the body. This is done through unintentional, abrupt, and random movements of body parts. Additionally, imaging techniques used in the medical field are also utilized to determine the extent of caudate nuclei atrophy. Such medical techniques include computerized tomography (CT) as well as magnetic resonance imaging (MRI). These can reveal early stages of HD as well as other underlying diseases (Rüb, Vonsattel, Heinsen, & Korf, 2015). However, these symptoms are not the ultimate diagnosis of Huntington's disease.
Huntington’s disease is a serious degenerative condition that requires early detection.
Since the HD causes slow and progressive loss of several body functions, it is essential to prepare the patient as well as the family about the end of life care that will be required. When this type of care is discussed early, it relieves the patient and the family of uncertainty. People with this kind of disease often have difficulty in communication and disorganized thought processes. For that reason, it is crucial to let them communicate their wills and other requirements before the disease reaches its advanced stages. Researchers also need to do a lot of work on the surviving neurons after striatal atrophy. This can help in the prevention of the various conditions that lead to faster degeneration of brain cells. Clear diagnostic procedures and guidelines should also be put in place to avoid misdiagnosis.
References
Bates, G., Tabrizi, S., & Jones, L. (2014). Huntington's Disease. Oxford: Oxford University Press.
Guillory, K., & Carasco, A. (2013). Huntington's Disease: Symptoms, Risk Factors and Prognosis. New York: Nova Science Publishers.
Rüb, U., Vonsattel, J., Heinsen, H., & Korf, H. (2015). The Neuropathology of Huntington’s Disease: Classical Findings, Recent Developments and Correlation to Functional Neuroanatomy. New York City: Springer Publishers.
