Essential tremor

Definition

Essential tremor is a hereditary hyperkinesis manifested by kinetic and postural tremors of the hands, head, lower jaw, lips, eyelids, vocal cords, and, less frequently, legs and trunk. It is diagnosed mainly clinically. Secondary-caused tremors are excluded with the help of biochemical tests, hormonal studies, MRI and CT of the brain, examination of cerebral vessels, and electroneurography. Therapy is carried out with beta-blockers, anticonvulsants, high doses of vitamin B6, and acupuncture. Targeted deep stimulation of extrapyramidal system structures may be used.

General information

A distinctive feature of this type of tremor is its manifestation with muscle tension and movement. The incidence of pathology increases with age. According to various data, among people under 40, essential tremor is observed in 0.3-6.7%, and after 70, in 8-17%. The morbidity statistics do not give exact figures because the benignity of tremors leads to a lower turnout of patients to doctors. There are also diagnostic errors—sometimes, tremor is treated as Parkinson’s disease.

Causes

The etiology of the disease is closely related to genetic disorders transmitted in an autosomal dominant manner. If one parent suffers from a tremor, the probability of its development in the child is at least 50%. Along with cases with hereditary predisposition, there are many sporadic forms when such pathology is not detected among the patient’s relatives.

Recent advances in genetics have made it possible to determine that several genes are responsible for the development of hereditary tremor. Apparently, gene aberrations lead to disorders in the extrapyramidal system, which regulates posture and muscle tone. The thalamus and subcortical nodes are morphologic structures of this system, but degenerative changes in them are detected on MRI in only a few patients.

Symptoms of essential tremor

The primary clinical manifestation is a small-amplitude tremor with a frequency ranging from 6 to 12 Hz. The hands are most often affected. It is clearly noticeable when the hands are stretched out in front of the body and held in this position (postural tremor). Intentional tremor is also characteristic – tremor during purposeful movements. In some cases, the tremor phenomenon is observed at rest. In all patients, these changes disappear entirely during sleep. Physical exertion and emotional experience can intensify tremor.

Essential tremor may involve the head, chin, lips, tongue. The tremor of the vocal cords causes voice vibration, disturbing the clarity of speech. Tremors of the legs and trunk are noted less frequently. Mild changes significantly do not affect the quality of life. Moderate tremor of the upper extremities complicates fine work and lead to changes in handwriting: letters become pointed, and there are no connections between them. Severe tremor reduces performance and may causedisability. Visible to others, tremor causes psychological discomfort. It is possible to develop mistrust, depressive neurosis, and hypochondria.

For a long time, essential tremor was considered a monosymptomatic disease. Recently, clinicians have been discussing the presence of clinical forms accompanied by other neurologic symptoms and psychiatric and cognitive changes. Ataxia, hearing loss, depression, phobic disorders, decreased memory, and attention are observed. However, it should be taken into account that in elderly patients, these symptoms are often due to dyscirculatory encephalopathy with chronic insufficiency of cerebral circulation and age-related degenerative processes.

Diagnosis

Essential tremor is diagnosed only after ruling out all possible causative diseases. It is based primarily on clinical features and anamnestic data, and the diagnostic process takes place in several stages.

1. Neurologist consultation. The patient’s neurological status is examined, his mental state is analyzed, and the neck is examined for changes in the thyroid gland. Physical examination helps determine the time of occurrence, the nature of the tremor phenomenon, and the sequence of involvement of different body parts. Objectively, a neurological examination revealed tremors in the fingers and hands in the Romberg pose when performing the finger-nose test. Trembling of the lower extremities is detected when performing the patellofemoral test. In a relaxed, comfortable position of the body, it disappears.
2. MRI of the brain or CT scan. The study visualizes brain structures and various cerebral lesions (tumors, degenerative changes, atrophic areas, signs of encephalitis, etc.).
3. Ultrasound diagnostics. Ultrasound and duplex scanning of cerebral vessels help assess the state of cerebral blood circulation. Ultrasound of the thyroid gland is performed according to indications and can be supplemented by consultation with an endocrinologist.
4. Electroneurography – allows you to rule out polyneuropathy.
5. Laboratory studies: biochemical analysis of blood, study of thyroid function, determination of the parathormone level.
6. Genetic counseling and genealogical research are required to confirm the condition’s genetic nature. The presence of relatives with a history of similar symptoms supports hereditary tremor.

Differential diagnosis

The diagnosis of essential tremor is established after excluding the physiologic nature of the tremor and its connection with other diseases. Differential diagnosis is carried out with tremor in:

• lesions of the nervous system (parkinsonism, encephalitis, brain tumor, stroke, brain injury, multiple sclerosis, polyneuropathy, cerebellar diseases);
• endocrine disorders (hyperthyroidism, hyperparathyroidism, hypoglycemia);
• intoxications (alcoholism, uremia with renal failure);
• mental disorders (neurasthenia, hysteria);
• side effects of certain pharmaceuticals.

Tremor phenomena occurring against the background of the underlying pathology are usually combined with typical symptomatology. Psychogenic tremor is caused by stress, experiences, and mental abnormalities. Parkinsonism is characterized by resting tremors, accompanied by bradykinesia and muscle rigidity. Cerebellar ataxia is diagnosed by a characteristic gait, large-scale handwriting, and hypermetry of movements. However, it should not be forgotten that two diseases are possible in the same patient (e.g., essential tremor and Parkinson’s disease). Acute onset and association with a provoking factor (stress, traumatic brain injury, taking a pharmacological drug) confirms the secondary nature of tremor.

Treatment of essential tremor

Conservative therapy

Therapy is aimed at reducing tremor and slowing the progression of the disease. It has been carried out over the years. Includes pharmacotherapy, relaxing massage, and acupuncture. It is not recommended that patients experience increased physical and emotional stress. In drug treatment, the drugs of choice are:

• Beta-blockers have a good effect. They are prescribed for a long time and require mandatory monitoring of blood pressure and pulse rate.
• Anticonvulsants. Side effects (drowsiness and asthenia) are prevented by gradually carefully selecting the dose.
• Pyridoxine—High doses of vitamin B6 help significantly slow the progression of the disease. The drug is administered intramuscularly. The course of treatment lasts 1 month and is repeated annually 2-3 times.

In case of head tremor, it is possible to treat it by injecting botulinum toxin into the nodule muscles. The effect of the injection lasts up to 2.5 months, after which a second treatment is required.

Neurosurgical techniques

Severe essential tremor resistant to conservative therapies may be an indication for alternative therapies such as deep cerebral stimulation. Electrodes are implanted intracranially and connected to a small device that sends tremor-suppressing pulses. Recently, a group of researchers developed a method of ablation of certain areas of the thalamus passing through the bones of the skull with targeted ultrasound radiation. Developments in this direction are continuing.

All these treatment options are available in more than 570 hospitals worldwide (https://doctor.global/results/diseases/essential-tremor). For example, Functional neurosurgery can be done in 16clinics across Turkey for an approximate price of $5.7 K (https://doctor.global/results/asia/turkey/all-cities/all-specializations/procedures/functional-neurosurgery). 

Prognosis

Essential tremors usually have a benign course and can be treated well. Some patients do not seek medical attention for long, as they experience only minor discomfort. Without therapeutic measures, progression usually occurs, which may accelerate in old age. A pronounced tremor reduces the quality of life and ability to work, makes it difficult to care for oneself, and hurts psychological well-being.