Essential Tremor


Article Author:
Shashank Agarwal


Article Editor:
Milton Biagioni


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Steven Anderson


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Updated:
3/24/2019 11:28:29 PM

Introduction

Tremor is defined as an involuntary rhythmic and oscillatory movement of a body part with a relatively constant frequency and variable amplitude. Alternating contractions of antagonistic muscles cause it. Tremor is the most common of all movement disorders, and essential tremor is the most common neurologic cause of postural or action tremor. It usually presents as a bilateral postural 6 to 12 Hz tremor of the hands, followed by a kinetic and resting component. The upper limbs are often symmetrically involved, but with disease progression, the head and voice (less commonly legs, jaw, face, and trunk) may be involved. Although benign regarding its effect on life expectancy, it often causes embarrassment and, in a small percentage of patients, also serious disability. Symptoms are typically progressive and potentially disabling, often forcing patients to change jobs or seek early retirement.[1][2][3][4]

Etiology

The etiology of essential tremor is mostly unexplained. About half of the cases of essential tremor appear to result from a genetic mutation; although, a specific gene has not been identified. This form is referred to as familial tremor and is an autosomal dominant disorder. The variability in age of onset, the presence of sporadic cases, and incomplete concordance of essential tremor among monozygotic twins suggest that environmental factors play a role.[5][6][7][8]

Epidemiology

Essential tremor is the most common neurologic disorder that effects postural or action tremor. The worldwide, estimated prevalence is up to 5% of the population. Family history can be found in near 50% of cases and, in 90% concordance in monozygotic twins. The incidence of essential tremor increases with age, although it often affects young individuals, especially when it is familial.

Pathophysiology

Some reports suggest that the neuropathology of essential tremor is localized in the brainstem (locus coeruleus) and cerebellum, but the presence of cerebellar pathology is controversial.

History and Physical

Essential tremor most often affects the hands and arms bilaterally and is symmetric, but cases of asymmetric essential tremor have also been reported. In cases of asymmetric essential tremor, the tremor was more severe in the non-dominant arm. It can also affect the head and voice, and uncommonly, the face, legs, and trunk. It varies from a low amplitude, high-frequency postural tremor of the hands to a much larger amplitude, a tremor that is activated by particular postures and actions. In most cases, the tremor frequency of essential tremor is 6 to 12 Hz. essential tremor becomes apparent in the arms when they are held outstretched; it typically increases at the end of goal-directed movements such as drinking from a glass or finger-to-nose testing. Amplitude tends to increase with age while frequency tends to decrease with age. Although there are large variations in tremor amplitude and disability among patients with essential tremor, it is a disabling condition for a substantial proportion of affected individuals. A number of reports suggest that functional disability in essential tremor is associated with the amplitude of kinetic tremor in the upper limbs. Some patients with essential tremor develop enhanced physiologic tremor due to anxiety or other adrenergic mechanisms, thereby aggravating the underlying tremor. On a physical exam, essential tremor can be elicited during examination under 2 circumstances: with the arms suspended against gravity in a fixed posture and during goal-directed activity. Essential tremor is usually relieved by small amounts of alcohol (60% to 70%) but, in contrast with physiologic tremor, is not usually aggravated by caffeine. In some cases, additional cerebellar signs can be found like abnormal tandem walking and mild ataxia.

Tremor in the legs is unusual with essential tremor. A parkinsonian tremor is more likely if resting tremor is present in the legs. A tremor of the neck may be vertical ("yes-yes") near 25%  or horizontal ("no-no") near 75% and is usually associated with a tremor of the hand or voice. A tremor of the head rarely occurs in isolation in essential tremor. When it does, the possibility of cervical dystonia with dystonic head tremor should be considered.

Also, preliminary studies suggest that very mild cognitive deficits with reduced performance on tests of memory and frontal executive function may be more common in patients with essential tremor than age-matched controls, and that essential tremor may be associated with an increased risk of dementia and Parkinson disease.

Evaluation

The diagnosis of essential tremor is based upon clinical features and exclusion of alternative diagnosis. The core criteria require either a bilateral action tremor of the hands and forearms and absence of other neurologic signs. Other information strongly suggestive of essential tremor includes long duration (more than 3 years) of the tremor, a positive family history of essential tremor, and beneficial response to alcohol.[9][10]

The evaluation relies on a detailed neurologic examination to identify specific features of the tremor, including its frequency, amplitude, pattern, and distribution, and to identify other neurologic findings if present. Precipitating, aggravating, or relieving factors such as caffeine, alcohol, medications, exercise, fatigue, or stress should be elicited; a complete list of all medications should be reviewed to exclude the possibility of enhanced physiologic tremor.

There are no specific biomarkers or findings from neuroimaging or other ancillary investigations for confirming the diagnosis of essential tremor, but testing may be appropriate to exclude other causes of tremor. Laboratory evaluation may include tests of thyroid function, urinary copper, and ceruloplasmin to exclude Wilson disease, screening for heavy metal poisoning such as lead if any of these causes are suspected.

Brain imaging can be useful in patients suspected clinically of having a structural cause for tremors, such as Wilson disease, brain trauma, stroke, or mass lesion, but otherwise is not indicated. Striatal dopamine transporter imaging using Ioflupane I123 injection single photon emission tomography can reliably distinguish patients with Parkinson disease and other parkinsonian syndromes associated with nigrostriatal degeneration, for example, multiple system atrophy, progressive supranuclear palsy, and corticobasal degeneration from patients with essential tremor.

Treatment / Management

Less impaired patients may choose to skip treatment altogether. Some patients that are not functionally impaired desire treatment because their tremor is a significant source of embarrassment. Options for patients with significant functional impairment include non-medical, medical, or interventional therapy.

Non-Medical Therapy

In some patients, tremors can be reduced by weighting the limb, usually by applying wrist weights. In a small proportion of patients, this can dampen down the tremor enough to provide some relief or improve functioning. Since anxiety and stress classically make the tremor worse, non-medical relaxation techniques and biofeedback can be effective in some patients. Medications known to make tremors worse should be eliminated or minimized when possible. People with tremor also may benefit from avoiding dietary stimulants, such as caffeine. There are several commercially available technologies to help stabilize the use of utensil, like weighted utensils, or active cancelation of tremor technology to dampen tremor, which could be helpful for some patients.

Medical Therapy

The therapeutic approach to essential tremor many times follows a trial and error approach, and patients should be challenged by several medications if the first choice is ineffective or associated with debilitating adverse effects. Medical therapy can be divided into first, second, and third-line therapies.

First-line therapy: It is either approved by the FDA or supported by double-blinded, placebo-controlled studies that meet criteria for the class I evidence. This class of medications includes propranolol and primidone. If both primidone and propranolol are not effective alone, combinations of both may provide relief in selected patients.

Second-line therapy: Second-line therapy is supported by double-blinded, placebo-controlled trials that do not meet other requirements for the class I evidence studies. This includes gabapentin, pregabalin, topiramate, benzodiazepines (clonazepam, alprazolam), beta-blockers (atenolol and metoprolol) and zonisamide.

Third-line therapy: These therapies are based on open-label studies or case series. Drugs in this class include nimodipine and clozapine.

Interventional Therapy

For patients who fail pharmacologic treatment with the above drugs or are unable to tolerate the side effects, surgical options include deep brain stimulation (DBS), focused ultrasound, or radio-surgical gamma knife thalamotomy to treat persistently disabling limb tremor, and botulinum toxin injections to treat persistently disabling head or vocal cord tremor.

Botulinum neurotoxin (BoNT) injections: In some patients with severe head or hand tremors, injection with botulinum toxins can be helpful. BoNT should be considered as a treatment option for essential hand tremor in those patients who fail treatment with oral agents (Level B). A recent evidence-based review reported insufficient evidence to conclude the use of BoNT in the treatment of head and voice tremor.

Deep-brain stimulation: This is the most common surgical treatment for essential tremor. Most series report 70% to 90% hand tremor control. In deep-brain stimulation, electrical stimulation is delivered to the brain through an electrode implanted deep into the ventral intermediate nucleus (VIM) of the thalamus. This is typically done by implanting 4 electrodes in the VIM using stereotactic methods. Computerized programming of the pulse generator is most commonly done with a handheld device after the patient leaves the hospital to optimize the electrode montage, voltage, pulse frequency, and pulse width. Deep-brain stimulation can be done unilaterally or bilaterally depending on patients symptoms. There is an increased risk of speech and balance difficulties with bilateral procedures. If the tremor significantly affects both hands, the dominant hand is targeted, bilateral procedures may be considered.

Thalamotomy: Stereotactic surgical techniques can be used to create a lesion in the ventral intermediate (VIM) nucleus of the thalamus.

Focused ultrasound: Approved by the FDA in 2016, magnetic resonance imaging-guided, high-intensity, focused ultrasound thalamotomy is an innovative method for the treatment of essential tremor. Although it is transcranial and does not require an incision, skull penetration, or an implanted device, it is an invasive therapy that produces a permanent thalamic lesion.

Radio-surgical gamma knife thalamotomy: Gamma-knife thalamotomy fo­cuses high-energy gamma rays on the ventral intermediate resulting in the death of neurons. It is an unproven treatment that has not generally been adopted due to concerns about potential radiation side effects, including a theoretical, long-term risk of secondary tumor formation.

Differential Diagnosis

Conditions to consider in the differential diagnosis of essential tremor include the following:

  • Physiologic tremor: Predominantly bilateral, symmetrical action tremor. High frequency (10 to 12 Hz), the presence of known cause (e.g., medications, hyperthyroidism, hypoglycemia)
  • Parkinson Disease Tremor: Predominantly at rest, asymmetrical.  Usually does not produce head tremor. Frequency 4 to 6 Hz.
  • Orthostatic tremor: Postural tremor in the torso and lower limbs while standing; may also occur in the upper limbs. Suppressed by walking. Tremor is high frequency (14 to 20 Hz) and synchronous among ipsilateral and contralateral muscles.
  • Cerebellar tremor: Postural, intention, or action tremor. Relatively low frequency (3 to 4 Hz). Associated with ataxia and dysmetria
  • Writing tremor (task-specific): Not evident in other tasks requiring coordination, only during writing. Is considered a variant of focal hand dystonia (Writer’s cramp).
  • Psychogenic tremor: It is not an exclusion diagnosis. Symptoms vary in severity, depending on the subject’s emotional state associated with stressful life events. Several clues are helpful to differentiate the psychogenic nature and include sudden onset and spontaneous remission, larger variations of amplitude and frequency, and less severity. The tremors disappear with distractions such as alternate finger tapping, mental concentration on serial 7s, or the healthcare professional applying a vibrating tuning fork to a patient’s forehead and informing the patient (wrongly) that this can stop the tremor and entrainment. Entrainment is a change in frequency of a tremor in adaptation to voluntary movements such as a regular movement in the contralateral limb.

Prognosis

Although prospective longitudinal data are limited, the usual course of essential tremor is one of slow, gradual progression. Essential tremor may remain stable in a minority of patients. However, a stable course should raise suspicion for an alternative diagnosis such as an enhanced, physiologic tremor or drug-induced tremor rather than essential tremor. While prospective data are limited, essential tremor may be associated with an increased risk for developing Parkinson disease. Survival in essential tremor does not differ from the general population.

Enhancing Healthcare Team Outcomes

The management of essential tremor is multidisciplinary because of the diverse treatments available. For those not impaired by the disorder, only observation is recommended. There are both medical and non-medical therapies available for essential tremor, but there is no evidence to support one over the other. Because essential tremor can be affected by stress, education of the patient is important. The patient should refrain from caffeinated beverages, alcohol and limit stress. A multidisciplinary team of nurses, pharmacists, and clinicians will result in the best management and safety of these patients.

Medical therapy is usually pharmacological but lately invasive procedures like transcranial brain stimulation, deep brain stimulation and botulinum toxin are being used. The prognosis for most patients is guarded because there is evidence that essential tremor may degenerate into Parkinson disease. [11](Level V)


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Essential Tremor - Questions

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What is the best treatment of essential tremor in a patient with bradycardia?



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A 60-year-old man experiences trembling hands, which was initially intermittent but has become constant over the past several months. His tremor worsens when he is upset and improves when he consumes alcohol. Recently, he has noted a vocal tremor. Which of the following is the most likely diagnosis?



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Which of the following does NOT characterize an essential tremor?



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Which of the following tremors can be treated with beta blockers?



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A 41-year-old male develops a tremor of the left hand. The tremor disappears at rest and is evident when using the hand to grab objects. There are no other symptoms, and the neurologic exam is normal. His father had a similar tremor. What is the most likely diagnosis?



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Which of the following is not used to alleviate essential tremor?



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A 45-year-old female presents with a 2-year history of progressive hand tremors. It has become socially embarrassing as she has problems with eating and drinking. Small amounts of alcohol seem to help. Exam shows a mild head tremor. There is no tremor of the hands at rest but if held outstretched there is a course tremor. No other findings are present. What is the most likely diagnosis?



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What is the most common cause of tremor in the elderly?



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Which of the following is NOT true regarding essential tremor?



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Which of the following medications is the most appropriate treatment of essential tremor?



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Which of the following can be used to treat essential tremor?



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What is the best initial treatment for essential tremor?



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Essential Tremor - References

References

Pahwa R,Dhall R,Ostrem J,Gwinn R,Lyons K,Ro S,Dietiker C,Luthra N,Chidester P,Hamner S,Ross E,Delp S, An Acute Randomized Controlled Trial of Noninvasive Peripheral Nerve Stimulation in Essential Tremor. Neuromodulation : journal of the International Neuromodulation Society. 2019 Jan 30;     [PubMed]
Prasad S,Bhalsing KS,Jhunjhunwala K,Lenka A,Binu VS,Pal PK, Phenotypic Variability of Essential Tremor Based on the Age at Onset. The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques. 2019 Jan 28;     [PubMed]
Brogley JE, DaTQUANT: The Future of Diagnosing Parkinson's Disease. Journal of nuclear medicine technology. 2019 Jan 25;     [PubMed]
Iacono MI,Atefi SR,Mainardi L,Walker HC,Angelone LM,Bonmassar G, A Study on the Feasibility of the Deep Brain Stimulation (DBS) Electrode Localization Based on Scalp Electric Potential Recordings. Frontiers in physiology. 2018;     [PubMed]
McKinnon C,Gros P,Lee DJ,Hamani C,Lozano AM,Kalia LV,Kalia SK, Deep brain stimulation: potential for neuroprotection. Annals of clinical and translational neurology. 2019 Jan;     [PubMed]
Benito-León J,Serrano JI,Louis ED,Holobar A,Romero JP,Povalej-Bržan P,Kranjec J,Bermejo-Pareja F,Del Castillo MD,Posada IJ,Rocon E, Essential tremor severity and anatomical changes in brain areas controlling movement sequencing. Annals of clinical and translational neurology. 2019 Jan;     [PubMed]
Vogelnik K,Kojovic M, From beta-blockers to Parkinson's disease in respect of essential tremor. Movement disorders : official journal of the Movement Disorder Society. 2019 Jan;     [PubMed]
Prasad S,Pal PK, Reclassifying essential tremor: Implications for the future of past research. Movement disorders : official journal of the Movement Disorder Society. 2019 Jan 17;     [PubMed]
Tarakad A,Jankovic J, Essential Tremor and Parkinson's Disease: Exploring the Relationship. Tremor and other hyperkinetic movements (New York, N.Y.). 2018;     [PubMed]
Louis ED, The Roles of Age and Aging in Essential Tremor: An Epidemiological Perspective. Neuroepidemiology. 2019 Jan 9;     [PubMed]
Ross JP,Mohtashami S,Leveille E,Johnson AM,Xiong L,Dion PA,Fon E,Dauvilliers Y,Dupré N,Rouleau GA,Gan-Or Z, Association study of essential tremor genetic loci in Parkinson's disease. Neurobiology of aging. 2018 Jun;     [PubMed]

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