Master the diagnosis and treatment of essential tremor

Essential tremor (ET), also known as essential tremor, is the most common form of tremor in humans
.

Given its highly exposed neural manifestations and seemingly straightforward phenotype, the disease appears easy to diagnose
.

However, 30% to 50% of patients with an initial diagnosis of essential tremor end up with a completely different diagnosis after further evaluation, mainly Parkinson's disease and dystonia
.

Therefore, understanding essential tremor is helpful for the diagnosis and treatment of the disease
.

This article mainly describes the clinical features, auxiliary examination, diagnosis, differential diagnosis and treatment of essential tremor
.

Clinical features The clinical presentation of essential tremor is more nuanced than thought; in fact, the phenotype of tremor is multifaceted and highly patterned
.

The clinical presentation of essential tremor can be summarized in 13 sentences
.

 01 The core clinical feature is tremor in the arms and hands
.

Although upper extremity tremors in essential tremor are often described as postural or kinematic tremors, closer examination shows that kinematic tremors are always larger in amplitude than postural tremors
.

The central clinical feature of essential tremor is movement tremor in the arms and hands
.

This tremor can be observed when the patient performs a variety of daily activities, from eating to drinking to writing
.

These can be found in many neurological examinations (eg, finger-nose tests)
.

 The severity of this movement tremor varies and can be mild—nearly negligible and indistinguishable from normal physiologic tremors—or severe enough to interfere with daily activities
.


02 Upper extremity tremors are usually slightly asymmetrical
.

The upper extremity tremor in essential tremor is usually slightly asymmetrical rather than strictly asymmetrical
.

   03 When drawing a spiral, the waveform is usually aligned along one major axis rather than several
.

In essential tremor, motor tremors often occur during writing tasks, such as the Archimedes spiral or writing sentences
.

When a patient draws a spiral, the tremor waveform tends to line up along one major axis; however, in dystonic patients there may be several axes instead of one
.


04Many patients have upper extremity tremors that are intentional
.

In about half of patients with essential tremor, upper extremity tremor is an intentional tremor
.

There was mild or greater deterioration (ie, increased tremor amplitude) when the patient moved closer to the target on the finger-nose test
.

  05 The magnitude of postural tremor is generally smaller than that of motor tremor, and postural tremor in both arms is usually incoordination
.

In addition to upper extremity akinetic tremor, essential tremor is often associated with upper extremity postural tremor, which is not a motor tremor, although its amplitude is small and almost difficult to detect
.

Postural tremors in the arms are usually incongruous, such as a seesaw effect when the patient's arms are kept in a wing-beat position
.

   06 Postural tremor is greatest in amplitude at the wrist or elbow, including wrist flexion and extension movements
.

Postural tremor in essential tremor does not affect all upper extremity segments
.

Its maximum amplitude usually occurs at the wrist or elbow rather than the metacarpophalangeal joint, and it usually occurs during wrist flexion and extension rather than rotation-supination, although this is not always the case
.


07In longer and more severe patients, resting tremor may develop in the arms but not in the legs
.

The resting tremor of essential tremor is absent the main features of Parkinson's disease, such as retardation or stiffness
.

Unlike Parkinson's disease, resting tremor is a late feature in patients with essential tremor, who have significant movement tremors but only develop along the arms (ie, not the legs)
.

   08 Most people with essential tremor have tremors that usually get progressively worse over time
.

The tremor in essential tremor is not static
.

Most people with essential tremor have tremors that get progressively worse over time
.

   09 Over time, tremor spreads beyond the upper extremities to the craniofacial
.

In essential tremor, the tremor tends to spread beyond the upper extremities over time, and patients develop head tremors that involve the neck (most commonly), voice, or jaw
.

Early onset, marked head tremor without limb tremor is a hallmark of dystonia
.

Head tremors are especially common in women with essential tremor
.

  10 Unless the condition is particularly severe, neck tremor, known as postural tremor, resolves when the patient is supine with the head at full rest
.

Neck tremors in essential tremor usually begin as a unidirectional tremor, or as a "no-no" (ie horizontal) or "yes-yes" (ie vertical) tremor
.

The tremor can become progressively more severe over time, or it can evolve into a more complex tremor known as a mixed tremor, which is more difficult to describe
.

 11 Jaw tremors may occur in Parkinson's disease patients when their mouths are closed; in essential tremor patients, the mouth tremors occur when the mouth is opened
.

Jaw tremor occurs when the mouth is closed in people with Parkinson's disease, but essential tremor occurs when jaw tremor is more likely to occur when the patient's mouth is open (for example, during speech or when asked to open the mouth)
.

   12 Gait ataxia is a feature of essential tremor
.

Gait ataxia, another motor feature of essential tremor, manifests when patients walk in tandem
.

The ataxia in most patients with essential tremor is mild, although it can sometimes be of moderate severity
.

   13 Some patients may develop mild dystonia in the arm with prolonged severe tremors
.

Some patients may develop mild dystonia in the arm that has been experiencing severe tremors for a long time
.

This phenomenon is not surprising and may be because: (1) essential tremor is increasingly recognized as a disorder caused by abnormal or degenerative cerebellar lesions; (2) dystonia is also increasingly recognized Considered to be a disease partially caused by cerebellar dysfunction; (3) as essential tremor progresses, patients tend to exhibit graded and cumulative neurological signs (eg, intent tremor, resting tremor etc.
)
.

 Auxiliary examination 1.
Routine examination: blood, urine, stool routine, blood biochemistry (liver and kidney function, electrolytes, blood sugar, blood lipids), thyroid function,
etc.

The above inspections are generally normal
.

2.
Drug and poison detection: Exclude tremors caused by metabolism, drugs, poisons and other factors
.

3.
Serum ceruloplasmin: exclude hepatolenticular degeneration
.

4.
Others: including brain MRI scans, genetic studies, DAT or PET scans, nerve conduction studies/EMG, investigation of the cause of neuropathy, porphyria plaques,
etc.

5.
Clinical assessment: The clinical assessment tool for essential tremor is mainly a scale, and the assessment content mainly includes two aspects: assessment of the severity of tremor, assessment of dysfunction caused by tremor, and assessment of decreased quality of life
.

Commonly used scales such as Fahn-Tolosa-Marin tremor assessment scale [International Movement Disorders Society (MDS) recommendation], Bain-Findley tremor assessment scale (MDS recommendation), WHIGET tremor assessment scale (MDS recommendation) and so on
.

6.
Measurement methods of tremor: (1) EMG: ➤ Record the EMG of the muscle that produces tremor, that is, two groups of muscles with opposite actions are distributed on the opposite side of a motor axis, and these two groups of muscles with opposite actions are called Antagonist muscles; ➤ Surface electrodes and needle electrodes are usually used
.

Surface electrodes are non-invasive and record a wide range of muscle activity, but they often interfere with electrical signals due to motion artifacts; ➤ For polar EMG, it can record deep or small muscle tremors, and its advantages are accurate and reliable, with small artifacts , but invasive
.

 (2) Accelerometer ➤ Use the accelerometer to directly determine the acceleration of the tremor, acquire one-dimensional or three-dimensional accelerometer records, and complete the waveform analysis through Fourier transformation
.

 (3) Other measurement methods ➤ Drawing spirals and writing, pouring water experiment, drinking water experiment, upper arm stretching experiment
.

 Diagnostic criteria 1.
Diagnostic criteria: The clinical diagnosis of essential tremor needs to meet the following 3 points at the same time: (1) Action tremor of both upper extremities, with or without tremor in other parts (such as limbs, head or voice)
.

(2) Not accompanied by other neurological signs, such as dystonia, ataxia, Parkinson's syndrome, etc.

.

(3) The disease duration exceeds 3 years
.

 2.
Superposition of essential tremor: Features of essential tremor accompanied by neurological signs of uncertain clinical significance, such as tandem gait impairment, mild memory impairment, suspected dystonic posture,
etc.

However, studies have shown that the essential tremor superposition may represent only one state, that is, patients with essential tremor may develop these additional clinical features when the disease is advanced
.

 3.
Exclusion criteria: (1) There are factors that cause physiological hyperactive tremor, such as drug-induced, metabolic,
etc.

(2) Isolated focal tremor, such as tremor of voice, head, jaw, lower extremities,
etc.

(3) Isolated task or position-specific tremor, such as primary writing spasm, golfer,
etc.

(4) Orthostatic tremor with tremor frequency >12Hz
.

(5) Tremor syndrome with obvious other neurological signs, such as dystonic tremor syndrome, Parkinson's syndrome, and Holmes tremor
.

(6) Sudden onset or step-by-step progression of the disease
.

Differential Diagnosis 1.
Parkinson's disease: Parkinson's disease is more likely to have isolated resting tremor (ie, resting tremor without movement tremor), isolated postural tremor (ie, postural tremor with no or slight movement tremor), postural tremor Tremor primarily involving the metacarpophalangeal joints rather than the wrist, or postural tremor characterized by greater wrist rotation than flexion and extension
.

Another feature of Parkinson's disease is that when the tremor reappears, postural tremor begins after several brief incubation periods; whereas in essential tremor, postural tremor may vary over time, so it may not be present with lower amplitudes , and then after some time
.

In addition to tremor, patients with Parkinson's disease often have bradykinesia, muscle rigidity, and abnormal posture and gait
.

  Table 1 Differential diagnosis of essential tremor and PD tremor Disease-like manifestations and other cerebellar signs; cerebellar atrophy can be found on MRI or CT examination; genetic diagnosis can help differentiate
.

 3.
Hepatolenticular degeneration disease (Wilson disease): It can be manifested as resting, postural or motion tremor, often involving the distal upper extremities and head, and less frequently involving the lower extremities
.

A variety of neurological symptoms such as bradykinesia, stiffness, dystonia, chorea-like movements, facial expressions, athetosis, dysarthria, and dysphagia may also occur
.

In the early stage, there may be mild resting or postural tremor, and in the late stage, there may be proximal pterygoid tremor of the upper extremity
.

The characteristic K-F ring can be seen in the eye; MRI or CT examination can find abnormal signal of bilateral lenticular nuclei symmetry; genetic diagnosis is helpful for identification
.

 4.
Functional tremor: Also known as psychogenic tremor, it mostly occurs when there are certain mental and psychological factors such as anxiety, tension, and fear.
Compared with ET, its frequency is faster (8~12Hz) but the amplitude is smaller, and there is a corresponding Psychological characteristics of the disease, symptoms disappear after removing the precipitating factor, the most common factor is the increase of sympathetic nerve activity
.

 5.
Metabolic tremor: mostly postural tremor, the most common cause is hyperthyroidism, which causes high-frequency fine postural tremor of the upper limbs, often accompanied by other systemic signs, such as exophthalmos, sweating and weight loss
.

 6.
Drug-induced tremor: Common drugs include beta agonists, theophylline, antidepressants, thyroxine, and amiodarone
.

Drugs that block or inhibit dopamine can cause resting tremor and Parkinson's syndrome, including haloperidol, risperidone, tetrabenazine, cinnarizine, and flunarizine, among others
.

 7.
Dystonia: Features of essential tremor do not include tonic posture, movement, or tremor, except for mild tonic posture
.

In addition, tonic tremors themselves tend to be neither rhythmic nor oscillating
.

Although head tremor in patients is difficult to assess, the following points are worth considering: (1) Moderate or marked head tremor without limb tremor strongly suggests underlying dystonia
.

(2) Unless it is particularly severe, neck tremors in essential tremors—that is, postural tremors—should resolve with the patient supine with head resting; Potential diagnosis of dystonia
.

(3) Patients with neck tremor and those with a basic diagnosis of dystonia may have symptoms of dystonia, including head tilt or rotation, sternocleidomastoid hypertrophy, or other neck muscle hypertrophy
.

 Treatment of ET is divided into drug (oral drugs and botulinum toxin type A) treatment, surgical treatment, rehabilitation treatment and psychological counseling
.

 Treatment principles: (1) Mild grade 1 tremors that do not affect daily life or cause psychological distress do not require treatment, and only need to be taught and comforted; (2) Patients with grade 2 tremor can choose half an hour before the event due to work or social needs Take medicine to relieve symptoms intermittently; (3) Patients with grade 2-4 tremor affecting daily life and work need drug treatment; (4) Patients with severe tremor that is refractory to drugs may consider surgical treatment; (5) Head or voice tremor Patients can choose botulinum toxin type A injection therapy
.

  ➤ Drug therapy: See Table 2 for oral drug therapy
.

 Table 2 Commonly used drugs and precautions for essential tremor ➤Multi-point intramuscular injection of botulinum toxin type A: It can cause muscle relaxation paralysis by inhibiting the release of acetylcholine from the presynaptic membrane of peripheral motor nerve terminals
.

A single dose of 40~400IU of botulinum toxin type A can improve head tremor; multi-point injection of 50~100IU in the extensor and flexor muscles of the ulna and carpi radialis can reduce the tremor amplitude of the upper extremity, and the average treatment time is 12 weeks (usually 12 weeks).
4-16 weeks); 0.
6-15.
0IU soft palate injection can improve voice tremor, but adverse reactions such as hoarseness and dysphagia may occur; botulinum toxin type A treatment of refractory tremor is a symptomatic treatment measure, and usually the effect of one injection lasts for a long time 3 to 6 months, need to repeat the injection to maintain the effect
.

Allergic constitution and those allergic to this product are prohibited
.

 ➤Surgical treatment: Commonly used surgical methods include stereotactic thalamotomy, deep brain stimulation (DBS), and magnetic resonance imaging-guided focused ultrasound (MRgFUS) thalamotomy
.

➤Rehabilitation: 1.
Exercise therapy: Resistance training is the most common exercise therapy, including push-ups, dumbbells, barbells, etc.
, its purpose is to train the muscles of the human body, prevent limb spasm and joint stiffness; other exercise therapies include muscle strength training, Hand function training, joint range of motion training, posture training, balance training,
etc.

2.
Intelligent aids: For patients with severe tremor, anti-shake spoons, tremor orthoses, etc.
can be used to improve the quality of life of patients
.

➤Psychological counseling: Some patients with essential tremor have obvious anxiety, depression and other psychological disorders, which affect the quality of life of the patients to a certain extent
.

Therefore, the treatment of essential tremor should not only focus on improving the symptoms of the patient's tremor, but also pay attention to improving the patient's psychological problems such as anxiety and depression, and provide effective psychological counseling.
Reduce the psychological burden of patients, so as to achieve a more satisfactory treatment effect
.

  References: 1.
Chinese Medical Association, Journal of Chinese Medical Association, General Practice Branch of Chinese Medical Association, etc.
Guidelines for primary diagnosis and treatment of essential tremor (Practical Edition 2021) [J].
Chinese Journal of General Practitioners, 2021, 20(10):1037-1041.
2.
Parkinson's Disease and Movement Disorders Group of Neurology Branch of Chinese Medical Association, Parkinson's Disease and Movement Disorders Group of Neurology Branch of Chinese Medical Doctor Association.
Guidelines for the diagnosis and treatment of essential tremor in China (2020)[J].
Chinese Journal of Neurology, 2020, 53(12):987-995.
3.
Joaquim J.
Ferreira, Tiago A.
Mestre, Kelly E.
Lyons, et al.
MDS Evidence-Based Review of Treatments for Essential Tremor.
Movement Disorders, 2019.
4.
Elan D Louis.
Essential tremor: a nuanced approach to the clinical features .
Pract Neurol 2019;0:1–10.
The 7th Congress of Neurological Physicians.