Overview
Essential tremor (ET), also known as primary tremor, is a common movement disorder in which tremor is the only manifestation, with a prevalence of 0.3% to 1.7% in the general population. 1/3 or more patients have a positive family history of autosomal dominant inheritance. The pathogenesis is unknown. Idiopathic tremor is an autosomal dominant disorder and is the most common extrapyramidal disorder and the most common tremor disorder, with a family history in about 60% of patients. Idiopathic tremor is a single-symptom disorder, and postural tremor is the only clinical manifestation of the disease. Postural tremor is a tremor that is triggered when the limb is maintained in a certain position and disappears naturally when the limb is completely relaxed. Tremor in this disease is commonly seen in the hands, followed by tremor in the head, and in very few patients, tremor in the lower extremities. The tremor of this disease is aggravated by concentration, mental tension, fatigue, and hunger. In most cases, it disappears temporarily after drinking alcohol and worsens the next day, which is also a characteristic of idiopathic tremor. It should be treated symptomatically. Idiopathic tremor is also known as familial or benign idiopathic tremor, and postural or motor tremor is the only manifestation.
[Disease etiology].
More than 1/3 of patients have a family history with autosomal dominant inheritance, and 2 causative loci have been identified, localized at 3q13 (FET1) and 2p22-25 (ETM or ET2).
【Clinical manifestations】.
(A) General: The onset is insidious and slowly progressive. It can develop in all age groups, but is mostly seen in middle-aged and elderly people over 40 years old.
(B) Tremor characteristics: tremor frequency is 5-8Hz.
It is mainly manifested as postural tremor and/or motor tremor, which is reduced or disappeared when relaxed or at rest or in resting position, and aggravated when emotionally stressed, fatigued or examined. In some patients, tremor can be temporarily relieved after drinking alcohol.
(C) Tremor site: usually starts from one hand or forearm, and gradually extends to the ipsilateral upper limb and the contralateral upper limb, and also first appears from the head and neck. The main involvement sites are usually: upper limbs (95%), head (34%), lower limbs (20%), speech (12%), face and trunk (5% each) in order.
(iv) No change in muscle tone or slow movement, etc.
[Diagnostic points].
(I) Diagnosis
The diagnosis of ET should be considered when middle-aged and elderly people frequently present with postural and/or motor tremor of the upper extremities without other neurological symptoms and signs, and abnormal laboratory test elements. Attention needs to be paid to differentiate it from Parkinson’s disease, hepatomegaly, and hyperthyroidism.
(II) Diagnostic criteria
The American Academy of Movement Disorders and the World Tremor Research Organization propose the following diagnostic criteria for ET.
1. core criteria ① motor tremor of both hands and forearms; ② no cogwheel phenomenon, not accompanied by other neurological signs; ③ or only head tremor, but not accompanied by dystonia.
2. Secondary criteria ① duration of disease more than 3 years, positive family history; ② tremor reduced after drinking alcohol.
3. Exclusion criteria ① other neurological signs, or history of trauma shortly before the onset of tremor; ② physiological hyperactive tremor caused by drugs, anxiety, depression, hyperthyroidism, etc.; ③ history of psychogenic tremor; ④ sudden onset or segmental progression; ⑤ primary erect tremor; ⑥ only position-specific or target-specific tremor, including occupational tremor and primary writing tremor; ⑦ only speech, tongue, chin or leg tremor. chin or leg tremor.
Treatment options and principles]
Those with mild symptoms that do not affect work and/or life can be treated without medication, but those with significant symptoms need to be treated.
(I) Drug treatment
1. β-blockers
Propranolol (Propranolol), 10-20mg, 3 times a day, maximum 90mg/d. Can often cause slowing of heart rate. The following conditions are proposed as relative contraindications: (1) cardiac insufficiency, especially if not well controlled; (3) atrioventricular block of degree II-III; (3) asthma or other bronchospastic disease; (4) insulin-dependent diabetes mellitus, because propranolol blocks the normal adrenergic response to hypoglycemia in diabetic patients. The pulse must be maintained at 60 beats/min or higher. Other rare side effects include fatigue, nausea, diarrhea, rash, impotence, and depression. Arottnolol (Almal), a beta-blocker and adrenergic-only blocker, 10 mg 3 times daily, is more effective and has fewer adverse effects, but is more expensive.
2. Promethazine (paracetamol)
The use must start with a small dose (25mg/d) and slowly increase the dose, 25mg each time, until effective without adverse reactions, the effective dose is 150-350mg/d, the maximum dose does not exceed 250mg, 3 times a day (rarely used to this dose). Side effects include vertigo, nausea, and postural instability. If a single medication is not effective, a combination of propranolol and paracetamol may be tried.
3. Sedatives can be alprazolam 0.2-0.4mg/dose, clonazepam 0.5-1.0mg/dose, or phenobarbital 15-30mg/dose, 1/4-1/2 tablet each time, 3 times a day, maximum not more than 1 tablet/dose, 3 times a day. Adverse effects are mainly drowsiness.
4. Other drugs calcium antagonists flunarizine, nimodipine, nifedipine, carbonic anhydrase inhibitor vincristine can be applied.
(B) Non-pharmacological treatment
1. Botulinum toxin type A (BTX-A)
BTX-A local injection can effectively reduce tremor in the limbs, soft palate and other parts of the body, and the efficacy is maintained for about 3 to 6 months. The side effects have no serious adverse effects other than a certain degree of temporary muscle weakness.
2. Surgery For patients with severe unilateral ET for which formal drug treatment is ineffective, stereotactic surgery can be considered, and thalamic disruption is feasible, and deep thalamic electrical stimulation (DBS) is an effective alternative therapy.
The DBS surgical approach has outstanding advantages compared with disruption. First, DBS is reversible and modifiable. It is adjustable by setting the current, voltage, frequency, pulse width and electrode position of the deep brain electrodes. The stimulation parameters can be adjusted continuously as the disease changes, which can control the evolving idiopathic tremor symptoms in the long term. Secondly, DBS is developmental. Surgery preserves the neurological function of normal brain tissue, creating the conditions for possible new approaches in the future, and preserving the patient’s right to a new life and hope. Third, DBS is bilateral. The symptoms of patients with bilateral idiopathic tremor can be effectively controlled, while the destruction of bilateral pallidum or thalamus can easily lead to serious complications. In addition, DBS has few side effects, which is an important reason for patient acceptance. Because of these advantages, few people in developed countries such as the United States, Canada and Europe have undergone destruction and more and more patients with idiopathic tremor are treated with pacemakers.
The battery of a pacemaker system usually lasts 5 to 10 years, and if the battery is depleted, the pulse generator needs to be replaced, but the electrodes and leads do not need to be replaced. This can be replaced with a simple surgical procedure.