Disclaimer: The information provided herein is for educational purposes only and is not intended to replace the advice of a physician or other qualified medical professional.
Here is the entire book about essential tremor (ET) in a concise presentation.
Definition
Essential tremor, also known as familial tremor or idiopathic tremor, is a common neurological movement disorder that causes involuntary, rhythmic, oscillatory movement of a body part. ET used to be referred to as a “benign tremor,” but that term is now considered obsolete.
Features of the condition
Essential tremor is the most common tremor in humans
“The traditional view of ET, as a monosymptomatic condition (characterized by only kinetic or postural tremor), is being replaced by an appreciation of the spectrum of clinical features, with both motor and nonmotor elements” (E.D.Louis)
“The hallmark motor feature of ET is a 4–12-Hz kinetic tremor (i.e., a tremor that occurs during voluntary movements such as writing or eating) that involves the hands and arms, but which may also eventually spread to involve the head (i.e., neck), voice, jaw, and other body regions” (Louis et al, 2013b)
A difference in ET symptoms may be observed when comparing the left vs the right side of the hands and/or forearms
Many ET patient tremors have an intentional component where the amplitude of tremor increases as a target is approached
95% of ET patients experience symptoms primarily in their hands/ arms
Essential tremor is less commonly seen in the head/voice/face/trunk
If the tremor is isolated to the head and/or voice, it is likely NOT ET
Head tremors are more commonly seen in females
Patients with ET rarely suffer from tremors in their legs
Tremors are usually absent during sleep
Although ET has been reported to start at any age from adolescence onwards, the age of onset shows an early peak before 24 and a late peak after 46
There is emerging evidence that late-onset ET is associated with a slightly higher mortality rate, a slightly higher risk of mild cognitive impairment and dementia, and a more rapid progression of ET symptom
Early-onset patients more frequently reported a family history of ET
ET has a strong genetic component (familial tremor)
There is a family History in 30-70% of cases, with hereditary connections as high as 80% if the onset occurs before age 40
The inherited variety of essential tremor is an autosomal dominant disorder (i.e. An altered gene from just one parent is needed to pass on the condition)
Studies of identical twins have not conclusively identified a genetic component
The condition may stem from a possible under-regulated Cerebellum involving Purkinje cells and GABA (Gamma-Aminobutyric Acid)
Damage and/or death of Purkinje appears to be related to increase in tremors over time
Few long term studies of essential tremor exist, but the best estimates of average annual increase in tremor severity is between 3.1% and 5.3%
Types of tremors
Resting tremors are very rare with ET - They are more common in Parkinson’s patients
Postural tremors occur while a body part is held in a stable position against gravity.
Action tremors, brought on by voluntary movement, are usually the strongest. (i.e. tremors with the largest amplitude)
Intentional tremors are a worsening of action tremor as the hand approaches a target. (i.e. movement such as bringing the finger to the nose)
Isometric tremors happen when you contract a muscle against an unmoving object
Factors that exacerbate ET symptoms
Stress
Anxiety
Pain
Caffeine
Epinephrine/Adrenaline (commonly found in the anesthetic injected during dental procedures)
Diagnosis
Overall
The diagnosis of ET is made by evaluating the patient’s history of symptoms and by conducting a neurological evaluation. At present, there remains no medical test to independently validate a clinical diagnosis of ET
Specific diagnostic procedures
Finger to nose then finger to observer’s finger tip
Tracing a spiral or figure 8
Holding a plate by the edge
Drinking water out of a paper cup
Holding arms out in a “salute” posture at chest height
Noting whether symptoms decrease after the consumption of alcohol
Treatment
Drugs
Efficacy
Most effective in reducing hand tremor - Not as effective at treating tremor in the “midline” (voice, head, trunk)
Types
Propranolol (a beta blocker)
The only FDA approved drug for ET
The only “as needed” option (non-extended release version)
Lasts 4-5 hours
Extended release (24h) is available
60-320 mg/day
About 50% of people with ET respond to beta blockers
Beta blockers can reduce the amplitude of limb tremors by about 50%
Atenolol (a beta blocker)
A beta blocker that is preferred for patients with asthma
Primidone (barbiturate type antiepileptic)
As much as 750 mg/day, though commonly 500mg/day
Limb tremor reduced by 50% and may help with voice
Side effects are worst at start of treatment
Cannot be given with anticoagulants (Warfarin, Heparin, Plavix, etc.)
Needs a “ramp up” to start and a “ramp down” to stop safely
Gabapentin (anticonvulsants) and Topiramate (anti-epileptic)
Less well-tolerated and require ramp up to effective dosage levels
Clonazepam (benzodiazepines) and Alprazolam (psychotropic)
Less evidence of effectiveness in tremor reduction
Usually a “last resort” medication after all other meds have been tried
Can be habit-forming and have diminished effectiveness with prolonged use
Amantadine (antidyskinetic), Clonidine (antihypertensive), Acetazolamide (diuretic), Mirtazapine (antidepressant)
Not clear data to support their use
Botulinum toxin injections
Used for hand tremors but can cause weakness
Has resulted in improvement in head and vocal tremors
Alcohol
1 beer or 1 small glass of wine or 1 oz spirits
Can/may give relief within 15 minutes, for perhaps 1-4 hours
Watch out for a rebound the next day
Can lead to dependence
Drug in clinical trials (not yet approved)
PRAX 944: Reduces abnormal firing of neurons which cause tremor: Phase 3
BOTOX: Temporarily paralyzes muscles to stop tremors: Phase 2
SAGE-324: Reduces abnormal neural activity in the tremor circuit of the brain: Phase 2
ES-481: Anti-seizure medicine: Phase 2
Surgery
DBS
Usually not considered until other solutions (pharmaceuticals, adaptive devices, etc.) have failed to bring relief
First approved in 1997 by FDA for treating ET
Involves implanting electrodes into the thalamus in the brain and then attaching the opposite ends of the wires to a battery pack in the chest
Patients can opt to have only one side done (usually their dominant hand)
Bilateral DBS raises the risks of speech impairment and balance issues once the battery pack is turned on
Usually the wire(s) are implanted in one surgery, and then the battery pack in another surgery a few weeks later
Usually performed where the patient is awakened part way through to see if the electrodes are positioned properly
Can be performed while patient is fully anesthetized (much less common)
Patients use a remote device (iPod or an App on their phone) to control the battery pack
Some systems offer rechargeable battery packs that can last 10+ years before needing to be replaced
Standard battery packs usually last from 3-5 years before needing to be replaced
Statistics show that approximately 80% of patients experience an 80% improvement in their tremor
Generally, the risk of serious complications is relatively low, especially when performed by an experienced surgeon
Research is currently underway to improve the stimulation signal with a closed loop real time stimulus
Focused Ultrasound (non-invasive)
Uses MRI (Magnetic Resonance Imaging) to guide Focused UltraSound to target the area of the brain responsible for tremor
First approved in 2016 by the FDA for treatment of essential tremor (unilateral) and 2023 for bilateral treatment
Is not available for people with certain medical conditions, such as kidney disease, or those who can't undergo an MRI for any reason
Patients whose skull bones are too thick or too thin are also not good candidates for the procedure
Side effects
Patients may feel numbness or tingling in their fingertips
In 10-15% of cases, these sensations may be permanent
Temporary gait disturbance or imbalance may last for 1 or 2 weeks
Permanent unsteadiness has been reported in up to 10% of the patients
There is a very low chance of stroke or seizures
Orthosis Devices (a brace or other such device)
Heavy and bulky
Limit freedom of movement
Expensive
None approved by the FDA or CE (affirms the goods' conformity with European health, safety, and environmental protection standards)
Other devices
Cala Trio
Electrical Neurostimulation of the median and radial nerves at the wrist
40 minute session provides up to 90 minutes of relief
Expensive to run and service but some insurance plans do cover it..
Requires a prescription
Only available in the USA at present
Vibration technology
Gloves and Wristbands are under development
At least 4 active development groups
Not in clinical trials as of Q3 2024
Vilim ball
Anecdotal social media reports suggest this device may help with hand tremors
Local Vibrational Therapy for Essential Tremor Reduction: A Clinical Study Of the 17 persons that participated in the study: “Seven patients reported that vibrational therapy was not effective. Two patients reported an increase in tremor after using the device”
The CEO and CMO of the parent company are co-authors of the above review
ET vs PD
Although tremor is the primary symptom for both ET and PD, there are many differences in the signs and symptoms of the two disorders. ET often happens bilaterally and is primarily seen during action while PD’s tremor commonly occurs at rest and presents unilaterally and later progresses to both sides of the body. (Cheng F. et al.)
ET
The hallmark feature is a 4–12-Hz kinetic tremor (i.e., a tremor that occurs during voluntary movements such as writing or eating) that involves the hands and arms
Tremor is usually symmetric, whether action, postural, or isometric
Tremor amplitude can vary based on a number of factors
Stress
Time of day
Posture
Voluntary movement
Vocal tremors may be present
Onset can occur at any age
Family history of tremor reported in >50% of patients
Onset is commonly in middle age but can occur at any age, including childhood.
Often responds to a single measure of alcohol
May improve with the use of primidone or propranolol
Predominantly in the hands; sometimes in the head and voice; rarely in the legs
Handwriting tends to get large and shaky
PD (Parkinson's Disease)
Asymmetric resting tremors at a frequency of 3.5–7.5 Hz
Hallmark symptoms
Bradykinesia: slowness of movement
Rigidity/stiffness
Problems with walking/balance
Usually characterized by tremors when hands are at rest
A resting tremor that appears as if a person is rolling a pill or other small object between their thumb and index finger
There may be a re-emergent tremor (a postural tremor that appears after a delay) This delay may vary between a few seconds to several minutes
Voice and head almost never affected
Amplitude high/constant
Rarely a family history (<10%)
Onset generally between age 55 and 65
Does not respond to alcohol
Can improve with levodopa treatment
Hands affected more than legs; voice and head almost never affected
Micrographia (very small) handwriting is a symptom
Risk of developing PD is twice as high in men than women, but women have a higher mortality rate and faster progression of the disease
© 2024 James Kissel & Mark Honeyman
DOI: 10.5281/zenodo.13896283
This work is licensed under a Creative Commons Attribution 4.0 International License https://creativecommons.org/licenses/by-nc-sa/4.0/
