Movement Disorders

Movement disorders are a group of neurological conditions consisting of abnormal control of voluntary and automatic movements. They are classified as hyperkinesia or hypokinesia, depending on whether they imply excessive or diminished speed, range and/or accuracy of movements. Chorea and parkinsonism are the paradigmatic syndromes of these two categories. Movement disorders frequently involve neurological disorders. Parkinson’s disease and essential tremor, in particular, with a prevalence range of 1.7 and 4% among adults, are the two most frequent movement disorders.

Movement Disorders

When viewed from an anatomo-functional point of view, movement disorders are generally considered a disturbance of the basal ganglia or their connections with other brain structures. Mis-balance between two key basal ganglia neurotransmitters, dopamine, and acetylcholine, allows the dichotomy between hypokinesia (lack of dopamine, excess of acetylcholine) and hyperkinesia (the opposite), although many other transmitters, neuropeptides, and proteins have been implicated.
Progress has shifted in last few decades, bringing relevant knowledge of the genetic basis of movement disorders. Not surprisingly, the first movement disorders to be genetically characterized were those that had already, based on their description, been reported as being clearly familial, suggesting the presence of a Mendelian inheritance. Hence, Huntington’s disease, a dominant autosomal condition featuring a combination of chorea, psychiatric disturbances and dementia, was found in 1993 to be due to an excessive number of CAG repeats (polyglutaminopathy) within the huntingtin gene (chromosome 4)3.

Until recently, most of the remainder of movement disorders, namely Parkinson’s disease and atypical parkinsonisms, along with dystonia, have been considered as sporadic disorders until more recent analysis of familial cases has enabled the characterization of a number of classic Mendelian genetic mutations, mostly in PD and primary dystonia. Notwithstanding the undeniable relevance of the identification of these monogenic forms, these account for a small proportion of cases. Presently, increasing attention is being paid to the complex genetics of these disorders, emphasizing the common risk of these genetic variants are playing in the role of these disorders, rather than on rare genetic mutations directly and univocally causing them.
Relevant progress has been made in the knowledge of the genetic basis of movement disorders has been achieved by using various genetic studies which cause different Mendelian gene mutations. Growing attention is now being paid to the genetic risk variants of these of these diseases. In complex diseases like PD, a combination of genetic causative or risk factors and interactions between these risk factors could be involved in the etiology of the disease. Determining the prevalence of each disease, together with our assumptions about the characteristics and frequencies of the genetic variants in the affected populations, is conditioning the research methods to be prioritized. Common genetic factors are also involved in different related diseases and could begin to show common pathological biological pathways. Findings in the parkinsonism-associated pathways will allow developing animal or cell models of these conditions, in order to focus research on “the related molecular mechanisms, which could eventually lead to the identification of therapeutic targets.”



Ataxia

Ataxia (meaning “without order” or “lack of order”) is a sign looked for on a neurologic exam that shows movement that is not coordination or gait that looks abnormal. This sign means that there is damage or dysfunction to the areas of the brain that control movement,
balance and coordination.

Dystonia/Muscle Spasms


Dystonia means "abnormal tone" that can happen in any body part. It is a movement disorder that results in constant or sporadic muscular spasms, abnormal postures, movements that occur over and over, and twisting. Common forms of dystonia are “writer’s cramp” and “torticollis". Many causes of dystonia exist, such
as, genetics, trauma, infections and certain medications.

Myoclonus


Myoclonus is a brief, uncontrolled contraction of a muscle or group of muscles. This jerky movement results from damage to the brain or spinal cord and has been linked to many diseases affecting the nervous system, such
as, Huntington’s disease, Parkinson’s disease, Alzheimer’s disease, multiple sclerosis, and many more.

Tics


Tics are a movement disorder that
cause sudden movement anywhere in the body. These movements differ from other movement disorders because the person intentionally moves. Tics are usually voluntary movements performed out of a sense of need to relieve the desire. Examples of tics include eye blinking, throat clearing, toe curling, abdominal tensing, vocal outburst, and many more. Tourette’s syndrome is the most severe form of tic movements.

Tremor


A tremor is an involuntary, rhythmic movement of one or more body parts. It is the most common movement disorder that can affect multiple body parts. The most commonly affected areas are the hands, head, face, vocal cords, trunk, and legs. A tremor can sometimes be a sign of another neurological disorder. There are many diseases that can cause a person to have a tremor including Parkinson’s disease.



Sources
https://www.ghc.org/kbase/topic.jhtml?docId=nord430
https://mdmercy.com/centers-of-excellence/additional-centers/interventional-pain-medicine/conditions-we-treat/osteoarthritis
https://www.healthtap.com/user_questions/674184-i-have-a-rash-on-the-back-of-my-leg-what-does-it-mean
http://europepmc.org/articles/PMC3681180/


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