What Are Movement Disorders?

A movement disorder is a neurological condition that affects your movement, either by increasing or reducing it. The affected movement can be voluntary or involuntary. There are many factors contributing to movement disorders, genetic factors, ageing, and brain trauma are typically mentioned. 

With millions of patients suffering from some kind of movement disorder globally, a better understanding of movement disorders may help overcome the challenges faced by patients and create a better living environment for them. 

This article discusses the various types of movement disorders, the mechanisms underpinning their development, and the symptoms associated with them. We will also explore promising pharmacological interventions and therapeutic techniques that are enhancing patients' lives.

Introduction

Movement disorders are a group of neurological disorders that affect your movement. These disorders can increase or decrease both conscious (voluntary) and subconscious (involuntary) movements. If you have a movement disorder, you may find it difficult to plan, control or execute various movements. This often manifests as symptoms like uncontrolled muscle contraction, uncoordinated balance, and even cognitive problems.

The Parkinson and Movement Disorder Alliance have suggested more than 40 million people are affected by movement disorders.¹ It is important to raise awareness of movement disorders and promote early diagnosis. As there is no complete cure for movement disorders yet, research into the development of effective treatments and preventative measures could significantly improve patient’s quality of life. 

Types of movement disorders

Movement disorders can be classified into three main categories: neurodegenerative, hyperkinetic (increased movement) and hypokinetic (reduced movement).  

Neurodegenerative movement disorders

The most common neurodegenerative movement disorders include Parkinson’s Disease (PD), Huntington’s Disease (HD) and Amyotrophic Lateral Sclerosis (ALS). In these neurodegenerative disorders, neurons (the main cells that make up our central nervous system) break down, degenerate, or die, affecting normal movement and activity. These neurodegenerative movement disorders mostly appear and progress as patients age. 

Parkinson’s disease

Parkinson’s disease is caused by the loss and lack of neurons in the basal ganglia (the region of the brain responsible for controlling movement) - specifically, the neurons responsible for producing dopamine.2 Individuals with PD may suffer from tremors in their limbs or jaw and experience difficulty in swallowing and chewing.

Huntington’s disease (or Huntington’s chorea)

Huntington’s disease is caused by a mutation in the IT1 gene, which affects the production of a protein called Huntingtin. This mutated product can negatively affect essential cellular functions and lead to neuron death.³ Huntington’s often appears early in adult life, with symptoms typically appearing around 37 years of age. However, this can vary.² Typical symptoms include involuntary twisting and jerking and unusual eye movement.

Amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is a disorder that disturbs and kills motor neurons (the neurons that control our voluntary muscle movements), making it difficult for patients to move.⁴ Symptoms of ALS include muscle weakness and cramps, difficulty swallowing, difficulty breathing, and cognitive changes.⁴  

Hyperkinetic movement disorders

Hyperkinetic movement disorders are often related to excessive involuntary movements. They can be an indication of deeper neurological diseases or injuries to motor neurons or can be induced by drugs, toxins, pressure, or infection. These disorders are more commonly observed in children with neurological disorders than in adults.⁵ These disorders include:

• Dystonia: A movement disorder that affects various muscle groups, leading to involuntary muscle contraction, repetitive movements, or abnormal posture, which may be painful.⁵  
• Chorea: A disorder that also involves discrete involuntary movements but is distinguished from others due to its unpredictability, starting and ending from different locations, and timing.⁵
• Myoclonus: A sudden and involuntary series of muscle contraction and relaxation which creates non-rhythmic muscle jerks. It can affect one or more muscles simultaneously in a predictable sequence (synchronous) or unpredictably.⁵

Hypokinetic movement disorders

Hypokinetic movement disorders reduce or completely impair a patient’s movement and can also be referred to as hypokinesia. The cause of hypokinesia is often associated with Parkinson’s disease due to its impact on the neurons that affect motor function, but it is also seen in other neurological conditions. The symptoms of hypokinetic movement disorders can be classified into bradykinesia and akinesia:⁶ 

• Bradykinesia: slow movement, or continued pauses or hesitations in your movement 
• Akinesia: the inability to perform certain movements. It can be grouped under bradykinesia. 

Causes and mechanisms of movement disorders

Although the exact mechanisms underpinning movement disorders are still unknown, most cases can be linked to genetic factors, neurochemical imbalances, brain injury, or other factors. 

Scientists have studied the genes thought to be involved in movement disorders and found that mutations in certain “risk genes” are major risk factors for, or directly cause these disorders. These mutations may produce faulty proteins that interfere with neurological pathways and cause damage to neurons and other cells. Known risk genes include the IT1 gene in Huntington disease, the C9ORF72 gene in ALS, and the SNCA gene in PD.^7,8

Clinical and preclinical studies have recorded the low levels of neurochemicals like dopamine, serotonin, and glutamate in the brains of patients with Parkinson’s disease and Huntington’s disease. This is not just symptomatic - the lack of these neurotransmitters and the neurons producing and using them contributes to the progression of movement disorders and further neuron loss.⁹  

Brain injuries can cause damage in or impairment to various regions of the brain, such as the thalamus and basal ganglia, leading to dysfunctional movement and movement disorders.¹⁰ Other factors thought to be involved in brain injury and movement disorder development include toxin buildup, side effects of medication, progression of other diseases.  

Symptoms of movement disorders

Typical symptoms of movement disorders include:¹¹ 

• Tremors: shaking in one or more parts of the body at rest or performing movements
• Muscle rigidity: muscle stiffness, which may make it hard for muscles to contract and relax and may cause pain or cramping
• Unstable posture: difficulty in remaining posture and balance under dynamic or static positions
• Altered gait: difficulty walking or changes in walking posture due 

Diagnosis and evaluation

The diagnosis of movement disorders requires taking a full medical history and physical examination, as well as neuroimaging and laboratory tests. A healthcare professional will initially evaluate your basic condition -  for example, seeing whether you are experiencing excessive or reduced movement, whether this occurs when you are asleep or awake, the body parts affected by your condition, and whether your movements are regular or random.¹⁰

Further tests may be used to assess the impact of your condition on your brain and neurons, your overall motor function, and your quality of life. Neuroimaging technologies like MRI and CT can provide a patient's brain condition, helping with diagnosis and evaluation of the loss of brain tissue and neurons in some situations.¹² Intellectual or cognitive function tests may be recommended for young children.⁵ 

Treatment and management

There is currently no cure for movement disorders, but there are pharmacological approaches and surgical interventions which can help control your symptoms and disease.

Medications focusing on the mechanisms of different movement disorders have been developed. For example, Levodopa and dopamine agonists are designed for Parkinson’s disease. These are often combined with physical therapy. Therapists provide exercises and activities that help to recover muscle strength and stimulate relevant pathways in the brain to increase accuracy of movements.¹³

Deep brain stimulation is currently one of the most beneficial surgical procedures for movement disorders. Its wide range of applications and generally low risk has made it a popular treatment for movement disorders, especially in cases where they seriously affect patients’ quality of life. Deep brain stimulation involves inserting a thin electrode into the affected regions of the brain and placing a battery in the chest. From here, the electrical stimulation of neurons can be controlled from a computer and optimised over time.¹⁴

Apart from medication and surgeries, lifestyle modification is also necessary for many patients. Following suitable diets and getting regular exercise may prevent symptom progression while increasing patients’ quality of life.¹⁵

Impact on quality of life

Movement disorders pose significant physical and mental challenges on patients and their families. Indeed, patients often suffer from depression and anxiety due to their reduced quality of life.

To draw attention to movement disorders, associations like the International Parkinson and Movement Disorder Society® have accumulated healthcare professionals and researchers who are dedicated to promote greater outcomes in this field and support patients. 

Summary

Movement disorders are a group of neurological conditions that impact your ability to control your movements, potentially leading to an increase or decrease in voluntary or involuntary actions. Diseases of this kind often have uncertain origins, but their onset can be shaped by a combination of genetic and environmental factors. Some of the most common movement disorders are Parkinson's disease, Huntington’s disease, and Amyotrophic lateral sclerosis. There is currently no cure for movement disorders, but researchers and professionals are fighting for better medication and diagnostic methods, allowing these illnesses to be diagnosed and controlled at an early stage.