Introduction
An individual with control over body movements can interact with people, objects, and the environment effectively. The brain’s motor system plans and coordinates movements and activities. The signal is then sent to the spinal cord to cause the contraction of specific muscles. Movement disorders are neurological conditions (originating from the central nervous system; CNS) that cause abnormal movements and alter movement coordination. Hence, damage or malfunction to brain areas that control movement results in a movement disorder. Advances in understanding the underlying disease mechanism of movement disorders provide clinicians with emerging options to improve the lives and outcomes of patients. Further, various tools and techniques can be used for diagnosis and severity assessment that can be useful for monitoring the progression or treatment of movement disorders.
How Are Movements Classified?
Human movements are grouped into intentional and unintentional movements. Intentional movements occur when one decides to move. Therefore, voluntary movement is a product of the coordinated operation of the CNS and is essential for achieving a particular goal.
Non-intentional movements have many kinds: reflexes and involuntary movements. Involuntary movements can also be produced by a non-intentional and pathological activation of CNS pathways. These comprise movement disorders.
What Are the Most Common Movement Disorders And Their Management?
The causes of movement disorders are genetics, infections, medicines, brain damage, spinal cord disorders, metabolic disorders, and toxins. The most frequently encountered movement disorders are:
1. Tremors: Tremors involve involuntary shaking movements that include one or more parts of the body. Tremors occur due to the repeated contraction and relaxation of the muscles. Tremors are categorized into essential and functional tremors. Essential tremors worsen when a patient attempts basic movements and occur when there is an underlying brain disorder. On the contrary, functional tremor does not involve an underlying structural brain disorder.
Physical therapy or lifestyle changes may improve symptoms. Medication is considered if the condition affects the patient’s quality of life. About 50 to 75 percent of patients taking medications have reduced tremors. Beta-blockers (block the effects of adrenaline), anti-seizure medications, and benzodiazepines (anti-anxiety medications) are prescribed. Botox injections block nerve and muscle communication and may decrease tremors.
If the tremor is severe to cause a disability, surgery may be recommended. Thalamotomy targets the thalamus (a brain area that receives sensory messages). About 75 percent of patients undergoing partial thalamotomy find relief on one side of their body. Bilateral thalamotomy (surgery on both sides of the thalamus) is rarely done due to speech loss risk. Deep brain stimulation (DBS) is another surgical option in severe essential tremor cases that do not respond to medication. A wire is implanted in the thalamus and connected to a neurostimulator under the collarbone. The neurostimulator interrupts signals that cause tremors.
2. Parkinson’s Disease: PD is a brain disorder causing uncontrollable movements and balance and coordination issues. It also causes cognitive decline (impairment in mental function).PD is a progressive disorder caused by nerve cell degeneration in the substantia nigra (a part of the brain that controls movement). These nerve cells die, losing the ability to produce dopamine (an important neurotransmitter). PD leads to muscle rigidity or limb stiffness, gradual loss of spontaneous movement, decreased mental skills, decreased facial expression, blinking, swallowing, and drooling frequency.
Patients also have flexed posture with bent elbows, knees, and hips and unstable walking. Essential tremor (classic pill-rolling movement) is present at rest in Parkinson’s disease (PD). It is a coarse and regular movement involving the thumb and index finger. About four percent of the patients are diagnosed before the age of 50. Most patients are treated with medications to relieve the symptoms of the disease. Some of them are dopamine precursors, dopamine agonists (mimic the effects of dopamine), and anticholinergics (can relieve the symptoms of PD). DBS is effective in treating all of the primary symptoms and allows for a significant decrease in medication doses. Further, thalamotomy can also stop tremors in PD.
3. Dystonia: Dystonia involves intermittent muscle contractions resulting in twisting, repetitive patterned movements, and abnormal postures. Most forms of dystonia do not have any cause. The disease mechanism of dystonia represents a brain network disorder involving the basal ganglia, cerebellum, thalamus, and cortex, resulting in abnormal neural motor programs.
The primary clinical features of dystonia include influence by voluntary action, unintentional muscle contraction, and tremors (oscillatory movements). Dystonia is exacerbated by anxiety, stress, heightened emotions, and fatigue. Therefore, dystonia decreases with relaxation and sleep.
The management of dystonia involves accurate diagnosis, identifying the form (idiopathic, genetic, or acquired), and determining whether it is combined with another movement disorder. The therapeutic approach involves botox injections, rehabilitation, and consideration of surgical therapies.
Ataxia: Ataxia (without coordination) is a degenerative disorder affecting the central nervous system. This can result in instability, imbalance, tremors, or impaired coordination of muscles. Movements are not smooth and may be jerky. Patients may fall frequently due to unsteady walking. The cornerstone of ataxia treatment is the use of oral Dopamine. Other medications include anticholinergics, dopamine agonists, selegiline (which increases dopamine in the brain), and entacapone (used to treat symptoms of PD).
Other less common movement disorders include Huntington’s disease (an inherited disease that causes nerve cell degeneration in the brain), Tourette syndrome (a condition that causes people to make sudden twitches, movements, or sounds), multiple system atrophy (MSA, a neurodegenerative disease affecting movements, blood pressure, and other body functions), and myoclonus (twitching or intermittent spasm of a muscle or group of muscles).
How Are Movement Disorders Evaluated?
Different tools and methods can be used for diagnosis and assessment of severity. They can further monitor disease progression or therapy.
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Electromyography (EMG): It is a valuable technique for movement disorder analysis. EMG evaluates the activity of muscles. Needle EMG is used for the analysis of neuromuscular disease (NMD).
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Kinesiology: It is the study of body movement and the measurement of forces that move. It is combined with EMG in the clinical investigation of movement and movement disorders. There are multiple methods for the measurement of body movements. Hence, they need to be carefully used to obtain accurate information.
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Nerve Conduction Studies (NCS): It determines how an electrical impulse passes through a nerve. NCS can identify nerve damage in various movement disorders.
Conclusion
A team of expert neurologists, neurosurgeons, physical therapists, speech therapists, and psychologists is required for the holistic treatment of a movement disorder patient. Hence, a crucial part of the treatment approach is adequately examining patients and reviewing investigations and imaging tests. As a result, it forms long-term relationships with patients by providing them with advice and education.
