Essential tremor: causes, evolution, disability, ultrasound, intervention

By Cristiano Antonino On Aug 9, 2022

Essential tremor (‘TE’) refers to one of the most common movement disorders, which manifests itself mainly as postural and kinetic tremor

Essential tremor is characterised by a persistent, bilateral tremor affecting the upper limbs and hands, but may sometimes be limited to the head only.

Objective examination shows no other findings, in particular no neurological signs or muscle rigidity.

It should be noted that tremor is generally classified as follows

rest tremor: typical of Parkinson’s and Parkinsonian syndromes;
postural tremor: this is evidenced by the patient stretching his arms forward and is found in anxiety, alcoholism, hyperthyroidism, hepatic encephalopathy, but may also be present in the elderly (senile tremor) or may have no apparent cause (essential tremor);
intentional (or kinetic) tremor: this is typical of cerebellar pathology and is evident during the execution of a movement. However, essential tremor can also be kinetic. It is not present during rest and when the patient is asleep.

Spread of essential tremor

TE affects between 0.5 and 6% of the population aged 40 years and over; it affects 15% of people aged 65 years and over (in this case we speak of ‘senile essential tremor’).

The incidence of TE increases with age, but it can occur at any age, even in youth or even in adolescence and childhood (albeit rarely).

Sixty per cent of hereditary cases begin at a young age; approximately 5 % of patients with onset of essential tremor are children or adolescents.

TE is spread equally between men and women (with a slight predilection for the male sex).

Essential tremor, causes and risk factors

The condition currently has no known specific causes, although it is assumed that among the predisposing causes are basically involved

genetic factors: familial essential tremor or hereditary tremor; the presence of a mutation in the Lingo1 gene would also appear to increase the risk of TE;
environmental factors: such as substances consumed in the diet – especially in the case of high consumption of certain types of meat containing armane, a carcinogenic heterocyclic alkaloid β-carboline amine, which is also present to a small extent in coffee, certain sauces and tobacco smoke) and has been found in 50 % of people with TE;
traumatic factors: traumas of various kinds (from sports accidents, falls or surgery) that create damage to the cerebellum appear to increase the risk of TE.

Characteristic of tremor

The main sign of TE is postural and kinetic tremor, localised mainly at

distal extremities of the upper limbs;
head (affirmation or negation movements);
voice.

It may be present simultaneously in the upper limbs and head, or there may be an isolated tremor of the upper limbs, but it may affect any muscle in the body.

There is no objective and persistent muscle weakness (hyposthenia), obvious paresthesias (with the exception of possible median nerve involvement) or changes in muscle tone (hypotonia and hypertonia) that are related to the syndrome.

Essential tremor is visible during movement or tension of the limbs (especially in the use of the hands), and may increase or decrease depending on the emotional condition of anxiety, fatigue, cold or intense heat, although it is always present and higher than normal physiological tremor.

Tremor and activity/intensity disorders may be worsened by:

mental/physical stress;
fatigue;
strong emotions;
hypoglycaemia;
heat;
cold;
caffeine abuse;
intake of lithium salts;
intake of various antidepressant and antipsychotic drugs.

Symptoms and signs of essential tremor

In addition to tremor, discussed in the previous section, TE can lead to other symptoms and signs in the patient, including olfactory dysfunction (anosmia) and neuropsychiatric symptoms of Parkinson’s disease, such as depression, apathy and anxiety.

The tremor usually begins in one upper limb and later moves to affect the other.

In the early stages, the disorder may be transient and appear for instance during periods of anxiety and/or stress.

Later, it tends to become continuous.

Although the symptom tends to worsen as the years go by, it is usually a benign condition, so many patients do not seek medical treatment for this disorder.

However, the presence of tremor can lead to difficulties in work and social activities, and in 15% of cases, a significant degree of disability can occur.

Essential tremor can be associated with other pathologies, including:

moderate idiopathic Parkinsonism: moderate or mild ‘Parkinsonism’ may develop in around 20% of patients. This term encompasses various pathologies similar to Parkinson’s disease but with a different course and origin, causing rest tremor, bradykinesia, rigidity, hypertonia, dysarthria, hypomimia (poor facial expressions), gait disturbances (present, however, in about 50 % of TE patients) spasms, dyskinesia, ease of cramping, slight balance disorders and orthostatic hypotension (in 70 % of Parkinson’s patients, then in 14 % of TE patients, with the possibility of headache, hyposthenia, dizziness, tinnitus, fainting and insomnia);
Parkinson’s disease: essential tremor can also occur in patients who already have Parkinson’s, in which case the subject has both types of tremor, essential and Parkinsonian.

TE can also be associated with numerous other neurological, psychiatric and orthopaedic conditions and diseases, including:

dementia;
mild cognitive impairment;
manic depressive bipolar disorder;
cramps and fasciculations syndrome;
cervical and cranial dystonia;
scribe’s cramp;
spasmodic dysphonia;
restless legs syndrome;
akathisia;
idiopathic essential myoclonus
depression;
chronic anxiety;
panic attacks;
obsessive-compulsive disorder;
personality disorders and alcoholism.

The diagnosis is based on the anamnesis (collection of all data about the patient and his history) and the objective examination (the actual examination).

During the objective examination, simple extension of the upper limbs in extension reveals postural tremor, while the index-nose test highlights kinetic tremor.

In some cases, examinations that may be useful in ruling out other pathologies are:

blood tests;
electromyography;
electroencephalogram;
magnetic resonance imaging;
computed tomography (CT) scan;
radiography;
myelography;
electrocardiogram;
ultrasound;
ultrasound with colordoppler
biopsies;
postural analysis;
vestibular examination;
lumbar puncture.

IMPORTANT: not all the examinations listed are always necessary.

Differential diagnosis

The main diagnostic-differential problem is to distinguish essential tremor from Parkinson’s disease; the latter is manifested by tremor at rest, with unilateral onset and low frequency (less than 7 Hz), and there is usually no familiarity, unlike essential tremor.

Furthermore, Parkinsonian tremor tends to decrease with movement, whereas essential tremor is highlighted by it, and increases after muscular exertion.

The use of SPECT with DATscan has made it possible to differentiate essential tremor from Parkinson’s disease and primary Parkinsonism: in Parkinson’s the aforementioned method shows a reduction in the dopamine membrane transporter (DAT) at the striatal level.

Other causes of postural-kinetic tremor, such as multiple sclerosis, brain or neural lesions, neuropathy, hypoglycaemia and hyperglycaemia (especially from diabetes mellitus), hyperthyroidism and autoimmune thyroiditis (or other thyroid dysfunctions that cause tremor), drug side effects (e.g. tardive dyskinesia), Parkinsonism, dystonic tremor, poisoning or drugs must also be excluded.

There are no specific markers that are characteristic of essential tremor in the blood or CSF.

Pharmacological and physiotherapeutic therapy

The medical treatment of essential tremor usually involves the administration of propranolol, a beta-blocker, or primidone, or both; other drugs such as benzodiazepines, gabapentin, clozapine, flunarizine, clonidine, and theophylline have been shown to be effective in the treatment of essential tremor, although they are statistically less effective than propranolol and primidone.

If one particularly suffers from hand or head tremor, botulinum may be administered to relieve symptoms by blocking certain muscles.

The anti-epileptic and mood stabiliser valproate may be used in cases of comorbidity with essential myoclonus and bipolar disorder.

Effective physiotherapeutic methods include physical therapy, which aims to restore muscle control, and in the presence of diaphragm tremor – the formulation of correct breathing.

Hand shaking can be partially eliminated by manipulating small objects and finger gymnastics.

The main condition for efficiency in this case is the regularity of the classes.

Various balneological procedures, in particular contrasting souls in sanatorium and spa treatment conditions, help well with this disorder.

In addition, it can be helpful to follow

special diets;
acupuncture;
relaxing massage;
acupuncture.

In the treatment of essential tremor, it is also possible to use traditional medicine, which includes bee venom therapy, leech therapy (hirudotherapy) and phytotherapy.

Traditional methods give a temporary result and should only be applied under the supervision of a specialist.

In addition, to relax your muscles, you can practise the oriental practices of self-control and relaxing self-training.

Thus, for example, yoga-mudra can significantly facilitate the state.

This Indian gymnastics uses various combinations of finger positions to harmonise the flow of internal energy flows in the body.

In severe cases of disease progression, when traditional conservative treatment does not produce results and a curative effect or for certain reasons cannot be prescribed (e.g. if one is allergic to drug components, severe liver, kidney or stomach disease), surgery is recommended.

Surgical therapy

In patients with severe disabilities who do not respond to medical treatment, surgery may be proposed.

The procedures performed are:

stereotactic thalamotomy: destruction of a brain area responsible for the interaction between the remaining areas (thalamic nuclei);
deep thalamic stimulation: introduction of electrodes connected to a device that produces electrical impulses to stimulate the nervous system.

In both cases, good results can be obtained, however thalamotomy can lead to complications such as dysarthria and cerebral haemorrhage.

Thalamic stimulation seems to have a lower frequency of adverse effects and has the advantage that it can be discontinued in the event of side reactions.

In any case, the indications and type of intervention must be assessed by centres experienced in the method, as these are options whose long-term efficacy and safety have yet to be determined.

Botulinum

Recently, botulinum toxin associated with haemagglutinin A has also been proposed.

It is administered by means of injections into the forearm muscles or at the level of the neck muscles in cases of head tremor.

The treatment is able to reduce the symptom but can cause limb weakness.

Moreover, the difficulty of finding doctors who practise this therapy is a limitation.

High-intensity focused ultrasound

High-intensity focused ultrasound (FUS) is still an experimental therapy subject to evolution.

Most of the patients who underwent successful FUS both worldwide and in Italy suffered from essential tremor.

So far, few patients with tremor-related Parkinson’s disease have been treated.

All patients have undergone FUS on one side only. The reason is that it has been observed in the past that bilateral lesions cause major deficits, e.g. loss of the ability to speak.

In truth, these are lesions caused differently and this does not necessarily have to be the case with FUS.

For example, at Besta there are positive experiences with bilateral radiosurgery.

However, at a round table at the last International Surgery Conference, it was decided not to take the risk and not to perform bilateral FUS.

After all, it is well known that one of the potential side effects of DBS, which blocks the subthalamic nucleus by continuous inhibitory stimulation, is dysarthria (difficulty in articulating words) and in some cases it is necessary to modulate the stimulation so as to achieve a compromise between motor benefit and speech impairment.

FUS was effective in controlling tremor (disappearance of tremor) in all patients in whom it was completed.

There are patients in whom the benefit persists three years after therapy, but there are cases in which it reappeared after one year.

It is likely that FUS will have to be repeated periodically in some patients

Side effects of ultrasound

During the ten seconds of ultrasound the patient has headaches and sometimes dizziness.

After the therapy there are different experiences: a Canadian surgeon reported some motor deficits, while in Italy only transitory paresthesias (tingling sensation) were reported.

Surgeons probably follow different protocols: in Italy there is an initial phase in which the nerve cells are only stunned in order to mimic the lesion, and if any side effects appear the therapy is stopped.

This prevents the risk of adverse events.

In contrast to DBS, there is no risk of bleeding or infection because the technique is non-invasive.

Complications

The main and only complication of the disease in question is the loss of human self-care and work capacity.

There are no preventive measures for this disease in the case of hereditary genesis.

In this case, genetic counselling for patients intending to acquire offspring can play a preventive role.

Furthermore, the progression of the disease can be prevented by avoiding stress and limiting the consumption of various stimulants, such as alcohol, tea or coffee.

If essential tremor affects the ability to work, the patient may receive a disability award:

The medical commission may assign a percentage of disability that, if it exceeds 46%, places him or her in the protected categories.

However, each case must be assessed individually.

To reduce tremor, it may be helpful to

avoid or limit caffeine and other exciting drinks or substances
avoid alcohol or take it in very small quantities (maximum half a glass of wine per day: in some cases it has led to a slight improvement in tremor)
get the right amount of sleep at night (at least 7 hours);
avoid prolonged sleep deprivation;
carefully regulate the sleep-wake rhythm;
avoid chronic psychophysical stress;
avoid excessive sudden physical exertion;
avoid chronic anxiety;
avoid drugs;
avoid cigarette smoking;
avoid sedentary living;
engage in regular and appropriate physical activity;
avoid excessively intense sports training;
eating and hydrating properly.