What is Essential Tremor? Diagnosis and Treatments
Tremor is one of the most common symptoms that occur alone or in combination with other symptoms various lesions of the nervous system, as well as often accompanying endocrine, somatic diseases, and various intoxications. An international research group defines tremors as rhythmic mechanical oscillations in at least one functional body area.
There are two main types of tremors, physiological and pathological.
- Physiological tremor exists in every healthy person. Its amplitude is so small that it is invisible to the naked eye; the frequency is from 8 to 12 Hz. An increased physiological tremor has an amplitude greater than usual but retains the same frequency. It can often be seen with the naked eye. Increased physiological tremor occurs in various conditions leading to the excitation of peripheral b-adrenergic receptors (exposure to increased doses of endogenous adrenaline with fear, excitement, and when taking drugs agonists of these receptors).
- Pathological tremor A tremor that occurs in various diseases is visible and has several clinical and electrophysiological characteristics that differ from physiological tremor. The defining differential diagnostic sign of tremor among another hyperkinesis (chorea, athetosis, dystonia, ballism, orthostatic myoclonus, tics, Parkinson’s disease) is its recurrent oscillatory nature.
If you or your family members have a tremor, you need to make an appointment with your doctor. Contact our doctors at Lone Star Neurology will conduct a thorough diagnosis using modern equipment and prescribe treatment.
Tremor is Distinguished by the Nature of the Manifestations
There are two types of tremor, rest and action. This indicates the state in which the manifestation of tremor begins.
- Rest tremor is a tremor that occurs when the muscles do not make active movements and are subject only to gravity. A decrease in resting tremor is observed with active voluntary movements, especially with precise targeted movements, to the complete disappearance of tremors. This type of tremor is most typical for Parkinson’s disease and other parkinson-like syndromes, accompanied by damage to the substantia nigra and basal ganglia.
- Action tremor is a pathological tremor that occurs during voluntary muscle contraction. It includes:
- Postural tremor occurs with active muscle tension directed against the forces of gravity;
- Isometric tremor, with muscle contraction, experiencing stationary resistance when interacting with a stationary object;
- Kinetic tremor during any voluntary movement.
The Main Types of Pathological Tremors
There are several main types of tremors that can have different causes.
|Essential tremor||Essential tremor is a syndrome characterized by an isolated bilateral tremor of the upper extremities, lasting at least three years, which can be combined with tremors in the head, larynx (tremor of the voice), or lower extremities. It is also called the orthostatic tremor. This pathology affects approximately 1% of the world’s population. Incidence increases with age, with most studies finding no difference in prevalence between men and women. Initial manifestations can occur in early childhood or the 2nd to 6th decade of life. The essential tremor history is characterized by a slow progression of intensity with age.|
|Parkinsonian tremor||Parkinsonian tremor (tremor in Parkinson’s disease). Patients with Parkinson’s disease may have a different tremor, but there is often a classic resting tremor in 40-60% of patients. The frequency of this type of tremor is 4–6 Hz. In some patients with Parkinson’s disease, resting tremor is combined with a kinetic tremor of the same frequency. In some cases of Parkinson’s disease, the frequency of postural tremor is higher than resting tremor (up to 9 Hz); sometimes, postural tremor prevails over resting tremor. This type is observed only in 15% of patients. In some of them, postural tremor exists long before the onset of resting tremor, causing difficulties in differential diagnosis with essential tremor.|
|Dystonic tremor||Dystonic tremor hyperkinesis is associated with some form of dystonia. It has a frequency of 4-10 Hz, is predominantly postural and/or kinetic, and is usually localized in the part of the body affected by dystonic hyperkinesis (limbs, neck, etc.). Sometimes this type of tremor occurs without manifestations of dystonia; it is usually observed in family members who suffer from torsion dystonia.|
|Cerebellar tremor||Cerebellar tremor. This term is often used as a synonym for intentional tremor. However, various clinical forms of tremor can be observed in the pathology of the cerebellum, for example, rhythmic oscillations of the head and trunk (titubation). An extremely low frequency characterizes cerebellar tremor, usually less than 4–5 Hz, which distinguishes this tremor from most other types of tremor hyperkinesis.|
|Orthostatic tremor||Orthostatic tremor is a rare syndrome in the form of pronounced instability when standing up from a prone or sitting position (transition to an upright position), accompanied by the tremor. Tremor is characterized by an unusually high frequency (13-18 Hz), recorded in all muscles but palpable only in the thighs and legs muscles. This type of tremor has a central origin; it is observed in middle-aged and older adults (usually without other neurological symptoms), often with certain abnormalities in the psyche.|
|Holmes tremor||Holmes tremor. A combination of resting tremor, postural and intentional tremor is characteristic. Hyperkinesis increases sharply while maintaining a fixed position of the limb on weight, leading to rough, large-sweeping arms, legs, and trunk oscillations. Low frequency is characteristic (<4-5 Hz). With Holmes’ tremor, the cerebellothalamic (upper leg of the cerebellum), nigrostriatal pathways, and other central nervous system structures are often involved in the pathological process.|
|Primary writing tremor||Primary writing tremor or tremor with other purposeful complexly coordinated movements. The typical frequency is 4-10 Hz. Such a tremor can sometimes appear during specific actions and when performing similar (imitating) movements affecting the same muscle group.|
|Drug-induced and toxic tremor||Drug-induced and toxic tremor. A variety of medications can cause different types of pathological tremors. Typical examples are parkinson-like tremor that occurs after treatment with neuroleptics or other antidopaminergic drugs in Parkinson’s disease, intentional tremor after the use of lithium salts, tremor after acute alcohol intoxication, etc.|
|Psychogenic tremor||Psychogenic tremor. This type of tremor has a variable frequency (from 4 to 10.5 Hz) and is characterized by the following features:
Orthostatic or Essential Tremor
Different types of tremors have been described above. But in this article, we will discuss one of the types, it is orthostatic or essential tremor. Let’s start with its peculiarities:
- Essential tremors are often familial with a typical autosomal dominant pattern. Genomic association studies have shown that several single nucleotide polymorphisms are associated with essential tremors. For example, a gene encodes a LINGO protein that appears to inhibit cell differentiation during development and axonal regeneration, and synaptic plasticity.
- The question of certain pathophysiological features of essential tremor or primary orthostatic is controversial. However, several pieces of evidence point to cerebellar dysfunction. Magnetic resonance spectroscopy showed decreased levels of N-acetylaspartate in the cerebellum, indicating neuronal dysfunction. Some histological studies have shown a loss of Purkinje cells in the cerebellum; dysfunction of γ-aminobutyric acid has also been noted in the cerebellum of people with essential tremors.
- The pathophysiology of essential tremor includes rhythmic activity in the cortical-ponto-cerebello-thalamocortical loop, although the origin of the oscillations is unknown. Resting cerebellar metabolism is high, increases with extension of the arms, and decreases with ethanol (suppresses essential tremor).
Essential Tremor Diagnosis
To diagnose orthostatic tremor or essential tremor, many tests need to be done so that the doctor can be sure of the correct diagnosis. Diagnostics should include the following analyzes.
- Routine laboratory tests, including measuring thyroid-stimulating hormone and electrolyte levels in the blood, as well as examining liver and kidney function, are integral components in the diagnosis of essential tremor.
- History taking should include:
- information about the age of onset of symptoms;
- family history and any exposure potentially causing tremors;
- medicines (eg, sodium valproate, selective serotonin reuptake inhibitors, sympathomimetics, or lithium);
- toxins (such as mercury, lead, or manganese).
- Neurologic examination should assess the topical distribution of the tremor and the state of activation (resting or intentional tremor), include an assessment of the tremor frequency range (low [<4 Hz], moderate [4-8 Hz], or high [> 8 Hz]), and assess any signs suggesting a systemic disease or other neurological diseases.
- It is necessary to assess the patient’s condition at initial and subsequent examinations to assess the effect of therapy using The Essential Tremor Rating Assessment Scale.
- Additional electrophysiologic studies, including superficial electroneuromyography and accelerometry to assess muscle activation, rhythm, and frequency characteristics, can help distinguish primary orthostatic tremor from cortical, functional, and increased physiological tremor.
Parkinson’s disease with a predominant tremor of action and little or no tremor at rest or bradykinesia can be distinguished from essential tremor by single-photon emission computed tomography using 123I-ioflupane, which assesses the distribution of dopamine transporters.
Treatment of Essential Tremor
Deep brain stimulation (unilateral and bilateral) and thalamotomy (unilateral only) are aimed at the thalamic nucleus ventralis intermedius that are used to treat an orthostatic tremor refractory to medication. Although conventional stereotactic thalamotomy was the first available interventional treatment for tremors, its use is limited to unilateral interventions due to the high risk of irreversible dysarthria or ataxia after bilateral thalamotomy.
In a randomized trial of patients with tremors, deep brain stimulation produced more significant functional improvements than thalamotomy. It resulted in fewer side effects such as dysarthria, sensory disturbances, and gait disturbances. However, after five years of follow-up, half of the patients with essential tremors who were prescribed deep brain stimulation had a decrease in the effect, which was explained by the progression of the disease or the development of tolerance to stimulation. Adverse events are more common with bilateral than unilateral deep brain stimulation.
Undesirable effects of deep brain stimulation may include:
- reversible stimulus induced by stimulation,
- tonic muscle contractions.
The Food and Drug Administration has approved a focused ultrasound device to treat primary orthostatic tremors that do not respond to drug therapy. It was developed based on the results of a randomized controlled trial in 76 patients with essential tremor in which unilateral thalamic thermoablation using focused ultrasound, guided magnetic resonance imaging contributed to a significantly greater reduction in hand tremor and improved quality of life at 12 months. The most common adverse events of focused ultrasound thalamotomy were postoperative paresthesia or numbness (38% of participants) and gait disturbance (36%). Twelve months after the intervention, the frequency of paresthesia or numbness was 14%, and the degree of gait disturbance was 9%.
Medication for Orthostatic Tremor
Propranolol and primidone are the two compounds with the highest evidence for the treatment of essential tremors by reducing the severity of upper limb symptoms.
In randomized controlled trials, the non-selective beta-adrenergic blocker propranolol is effective at doses ranging from 120 to 240 mg/day:
- in randomized controlled trials, the amplitude of tremor, measured by accelerometry, was reduced by an average of 55%;
- side effects include bradycardia and bronchospasm;
- in one small study, long-acting propranolol was as effective as short-acting drugs in reducing the amplitude of essential tremor.
Primidone, which is metabolized to phenylethylmalonamide and phenobarbital, was effective at doses ranging from 250 to 750 mg/day:
- the amplitude of the tremor decreases by 60%, which is similar to the effect observed with propranolol monotherapy;
- early side effects, including dizziness, fatigue, and malaise, were noted in 23–32% of patients at the start of primidone treatment (versus 8% in the propranolol group), but usually resolved after 1–4 days, and the majority of patients who had such effects continued therapy.
A randomized controlled trial of combination therapy with propranolol and primidone compared with placebo demonstrated a 70% reduction in tremor. However, despite this, in a survey of people who received propranolol or primidone, about half said they eventually stopped taking the drugs. The most likely reasons for stopping treatment are limited effectiveness and unacceptable side effects.
There are limited data from randomized controlled trials to support other drugs for essential tremor, including topiramate, alprazolam, gabapentin, and other beta-adrenergic blockers such as atenolol, nadolol, and sotalol.
Controlled studies have not shown significant benefits with other medicines.
Therapy of Orthostatic Tremor
The choice of first-line therapy should be made after consideration of contraindications (eg, symptomatic bradycardia or hypotension), and patient preference may also be considered after lightening the side effects of these drugs, such as dizziness, hypotension, and sedation.
For second-line orthostatic tremor therapy, it is recommended to switch to another first-line drug, unless contraindicated; if none of these have been effective on their own, combination therapy may be considered.
For patients with disabilities and lack of adequate response to pharmacotherapy, which also includes treatment with drugs with a lower level of evidence of efficacy, the option of deep brain stimulation or focused ultrasound thalamotomy should be considered after assessing the possible risks of surgery and the potential benefits.
- What is Parkinson’s disease?
Parkinson’s disease is a chronic, steadily progressive disease of the brain, which is accompanied by autonomic and mental disorders. Experts distinguish three groups of the disease, idiopathic, symptomatic (toxic, vascular, infectious, etc.), and degenerative.
- What are the symptoms of essential tremors?
Essential tremor is often characterized by only one symptom of tremor, which differs from resting tremor in Parkinson’s disease. It appears with muscle tension and movement of the limbs, more often the arms.
- What is the main manifestation of Essential tremor?
Essential tremor is the most common extrapyramidal and one of the most common neurological diseases; the main manifestation is progressive bilateral action (kinetic-postural) hand tremors.
- Why is tremor dangerous?
Tremors can be caused by various injuries to the brain stem, extrapyramidal system, or cerebellum. Dysfunction or damage to neurons causing tremors can result from trauma, ischemia, or metabolic damage, as well as from various neurodegenerative diseases.
- Why does the whole body tremble?
Tremor is a process of trembling of certain parts or the whole body, which is involuntary. The main cause of this disease is structural damage to those parts of the nervous system that are associated with muscle tone.
- What disease is causing the fine tremor and slow deterioration that extends to both hands?
These are symptoms of essential tremor, or it is also called orthostatic. If you or your relatives have similar symptoms, then immediately consult a doctor who can diagnose and prescribe treatment.