Tremor

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Tremor is a condition in which a person experiences shaking or trembling movements in various parts of the body, with the hands being the most commonly affected. However, it can also affect the arms, legs, head, vocal cords, and torso. These tremors can either be constant or intermittent. Tremors can occur independently or as a symptom of another underlying disorder.

Although tremors are not life-threatening, they can pose challenges and potentially lead to disabilities. Tasks like writing, typing, eating, shaving, and dressing may become more difficult for individuals with tremors.

Typical symptoms of tremor include:

1. Rhythmic shaking of the hands, arms, head, legs, or torso.
2. Shaky voice.
3. Difficulty with writing or drawing.
4. Problems holding and controlling utensils, tools, or other items.

Additionally, certain triggers, such as stress, strong emotions, physical fatigue, specific postures, or movements, can exacerbate tremors. It’s essential for individuals experiencing tremors to seek medical advice for proper diagnosis and management.

Types of Tremors

Tremors are classified based on when and how they are triggered, falling into two main categories: rest tremor and action tremor.

1. Rest tremor: This type of tremor occurs when the affected individual is at rest. It’s commonly associated with conditions like Parkinson’s disease.
2. Action tremor: This tremor happens when a muscle is voluntarily engaged. There are several subtypes of action tremor, each with its own characteristics:
   • Postural tremor: Arises when maintaining a position against gravity, like holding the arms outstretched.
   • Kinetic tremor: linked with any voluntary movement, such as moving the wrists up and down or opening and closing the eyes.
   • Intention tremor: This occurs when the individual makes a deliberate movement toward a target, like lifting a finger to touch their nose.
   • Task-specific tremor: Occurs only during particular goal-oriented tasks, such as handwriting or speaking.
   • Isometric tremor: Manifests during a voluntary muscle contraction without accompanying movement, like holding a heavy book steady in one position.

These types of tremors can vary in severity and impact on daily activities, and understanding the specific type can aid in diagnosis and management.

Tremor syndromes

Tremor syndromes are identified by the pattern of tremors they exhibit. Here are some of the most common types:

Essential Tremor:

• Description: characterized by trembling in both hands and arms during voluntary movements without other neurological symptoms. It can also affect the head, voice, or lower limbs.
• Onset: Typically starts during adolescence or middle age (around 40–50 years old).
• Progression: Can remain mild or slowly worsen over time.
• Cause: The exact cause is unclear, but it’s often associated with mild degeneration of the cerebellum. About 50–70% of cases are hereditary.

Dystonic Tremor:

• Description: It occurs in individuals with dystonia, a disorder causing overactive muscles and abnormal postures or movements.
• Onset: Usually appears in young or middle-aged adults.
• Affected Areas: Can affect any muscle, commonly the neck (cervical dystonia), vocal cords (laryngeal dystonia), or limbs.
• Relief: Tremors may lessen with relaxation or touching the affected muscle.

Cerebellar Tremor:

• Description: Characterized by slow, large tremors in the arms, legs, hands, or feet, often worsening at the end of purposeful movements.
• Causes: result from cerebellar damage due to various factors like stroke, tumor, injury, or chronic alcohol use disorder.

Functional Tremor:

• Description: Also known as psychogenic tremor, it can mimic any type of tremor and may vary in symptoms. It often starts suddenly and fluctuates widely.
• Characteristics: Tremors may increase with attention but decrease or disappear with distraction.

Enhanced Physiologic Tremor:

• Description: Involves fine, small tremors in the hands and fingers, typically not caused by neurological diseases but by reactions to drugs, alcohol withdrawal, or medical conditions.
• Reversibility: This can potentially be reversed by correcting the underlying cause.

Parkinsonian Tremor:

• Description: Commonly seen as an early sign of Parkinson’s disease, though not present in all cases. Tremors are most noticeable at rest, often resembling a pill-rolling motion between the thumb and finger.
• Spread: may start in one limb or on one side of the body and spread as the disease progresses.
• Aggravation is often worsened by stress or strong emotions.

Orthostatic Tremor:

• Description: A rare disorder characterized by rapid muscle contractions in the legs upon standing. Tremors typically cease when sitting or walking.
• Detection: Tremors may not be visible but can be felt by touching the thighs or calves or detected by a doctor using a stethoscope.
• Progression: In some cases, tremors may become more severe over time.

Who is at risk?

Tremors can affect individuals of all ages, but they are most commonly observed in middle-aged and older adults. Interestingly, tremors occur equally in both men and women.

Causes of tremor

The underlying cause of tremors often lies in issues within the brain regions responsible for coordinating movements. While many types of tremors have no identifiable genetic link, there are certain forms that seem to be inherited and can run in families.

Tremors can either manifest independently or as a symptom of other neurological conditions such as Parkinson’s disease, multiple sclerosis, or stroke. Additionally, they can be triggered by various medical conditions, including:

1. Medications: Certain drugs like asthma medications, corticosteroids, chemotherapy drugs, and medications used for psychiatric and neurological disorders can induce tremors.
2. Exposure to Toxins: Contact with heavy metals (such as mercury, lead, manganese, and arsenic), organic solvents, or pesticides may result in tremors.
3. Caffeine: Excessive consumption of caffeine can either cause temporary tremors or exacerbate existing ones.
4. Thyroid Disorders: An overactive thyroid gland can lead to tremors.
5. Organ Failure: Liver or kidney failure can damage specific brain areas, resulting in tremors or jerky movements.
6. Diabetes: Fluctuations in blood sugar levels, either high (hyperglycemia) or low (hypoglycemia), may provoke tremors or other involuntary movements.
7. Stress, Anxiety, and Fatigue: Emotional factors like stress, anxiety, or physical fatigue have been associated with tremors.

Diagnosing Tremors

To diagnose tremors, a doctor follows a comprehensive approach involving various assessments:

1. Physical Examination and Medical History Review:
   • The doctor conducts a thorough physical examination and reviews the individual’s medical history.
   • They assess muscle tone, strength, reflexes, balance, and speech during a neurological examination.
2. Characteristics of tremors:
   • Determining whether the tremor occurs at rest or during movement.
   • Noting the specific location of the tremor in the body and whether it affects one or both sides.
   • Observing the frequency and size (amplitude) of the tremor.
3. Laboratory Tests:
   • Blood or urine samples may be collected to rule out certain factors contributing to the tremor.
4. Diagnostic Imaging:
   • Imaging studies such as MRIs or CT scans can help identify any brain damage that may be causing the tremor.
5. Electromyogram (EMG):
   • This test measures involuntary muscle activity and muscle response to nerve stimulation. It helps identify any underlying muscle or nerve problems contributing to the tremor.
6. Functional Limitation Assessment:
   • Additional tests may be conducted to assess functional limitations, such as difficulty with handwriting or holding objects like a fork or cup.

Treatments for Tremors

While there’s no outright cure for most forms of tremors, several treatments can effectively manage symptoms. In some cases, if symptoms are mild, treatment may not be necessary, and addressing any underlying health issues can sometimes alleviate or reduce tremors.

1. Medications:
   • Beta-blocking drugs: These can be effective for essential tremor and certain types of action tremor.
   • Anti-seizure medications: sometimes prescribed if beta-blockers are ineffective for essential tremor.
   • Tranquilizers (benzodiazepines) may provide temporary relief but can have side effects like sleep disturbances and coordination issues.
   • Dopaminergic medications are used for Parkinsonian tremors associated with Parkinson’s disease.
   • Anticholinergic medications are employed for dystonic tremors in some cases.
   • Botulinum toxin injections are useful for dystonic head and hand tremors and, in some cases, essential tremors that are unresponsive to oral medications.
2. Surgery:
   • Deep brain stimulation (DBS) involves surgically implanted electrodes that send electrical signals to the brain to control tremors. It is often used for Parkinsonian tremors, essential tremors, and dystonia.
   • Radiofrequency ablation uses radio waves to disrupt nerve signaling in the brain, improving tremors on one side of the body.
   • Focused ultrasound is an MRI-guided treatment that creates lesions in the brain’s thalamus to alleviate tremors, particularly for essential tremors resistant to medications.
3. Lifestyle Changes:
   • Physical, speech, and occupational therapy: helps manage tremors and adapt to daily challenges.
   • Limiting caffeine intake.
   • Using assistive tools, such as special utensils designed to minimize tremors,.
   • Taking medications as prescribed and discussing any potential contributing medications with a doctor.
   • Stress reduction techniques to alleviate tremor aggravation.
   • Choosing clothing and footwear that are easy to manage.
   • Ensure adequate sleep and engage in regular physical activity to prevent fatigue and improve sleep quality.

Latest updates on tremor research

1. Understanding Brain Functions and Disease Markers:
   • Researchers are using advanced neuroimaging techniques to identify structural and functional changes in the brain associated with tremor.
   • Functional MRI technology helps in understanding normal and diseased brain circuit functions related to motor behaviors.
   • The development of digital tools for real-time monitoring of tremor outside clinical settings is underway to optimize treatment.
   • Studies on brain tissue from individuals with and without tremor aim to uncover brain changes linked to tremor and potential treatment targets.
2. Genetic Discoveries:
   • Essential tremor appears to have a significant genetic component, affecting multiple generations. Researchers are identifying genes associated with familial early-onset essential tremor.
   • Focus on multigenerational families with early tremor onset aids in detecting genetic connections.
   • Research investigates the impact of genetic changes on essential tremor development.
3. Medications and Treatment Methods:
   • While medications are effective in about 50% of individuals with tremors, research is ongoing to develop assistive and rehabilitative devices.
   • Studies explore the use of ethanol (alcohol) in managing essential tremor and its physiological effects on the brain to determine the optimal dosage and identify alternative medications without ethanol’s side effects.
   • Efforts are directed towards understanding the source of essential tremor, evaluating the effects of current tremor-suppressant drugs on the brain, and developing more targeted therapies.
4. Clinical Trials:
   • Clinical trials play a crucial role in advancing knowledge and improving care for tremors and related disorders.
   • Participation in clinical trials enables clinicians and scientists to learn more about tremor and develop better treatment options.
   • Volunteers of diverse backgrounds and health statuses are needed for clinical trials to ensure that treatments are safe and effective for everyone.

Sources:

• National Institute of Neurological Disorders and Stroke (NINDS)
• NHS.UK
• MSD manuals