Hand tremor is a tremulous hyperkinesis, manifested by stereotypically repeated contractions of the muscles of the hand. It can be primary or occur under the influence of a wide range of causes, in particular, metabolic or toxic damage, focal and diffuse diseases of the nervous system. Tremor is detected during neurological examination, its origin is helped to determine laboratory tests, neuroimaging and neurophysiological methods. The basis of the treatment strategy is conservative drug therapy, refractory cases require surgical intervention.
Essential tremor is a common cause of hand tremors in adults. In its development, the role of hyperactivation of cerebellar neurons, basal ganglia, and thalamocortical connections is assumed. The disease is usually considered as monosymptomatic, its only manifestation is hand tremor that occurs when moving and maintaining a posture (kinetic-postural). This trembling covers the wrist and metacarpophalangeal joints, has a frequency of 8-1 Hz.
Along with the tremor of the upper extremities, some patients have trembling of the voice, head, and less often of other parts of the body. Manifestations are aggravated by excitement, physical and mental stress, but decrease after alcohol intake. Over time, the intensity of the jitter may decrease and the amplitude increase. Sometimes in the clinical picture there are mild neurological symptoms: unsteadiness when walking, the “cog wheel” phenomenon, cognitive disorders.
The classic tremor in Parkinson's disease occurs at rest, with complete muscle relaxation, and has a frequency of 3 to 6 Hz. Most often, the hands are involved, sometimes the lower limbs, chin, lips. Trembling is due to degenerative changes in the extrapyramidal system. Hand tremor is asymmetrical, like "counting coins" or "rolling pills", disappears with the onset of movement. Years before the onset of other symptoms, postural trembling may occur.
In addition to hand tremor, slowness of movement (bradykinesia, hypomimia), and muscle rigidity are considered typical signs of Parkinson's disease. The flexion posture of the patient, shuffling gait and freezing when walking are characteristic. Non-motor symptoms are represented by autonomic, mental, sensory and other disorders. Patients suffer from cognitive impairment, depression, apathy. Among the frequent manifestations there is a violation of swallowing, leading to aspiration of food.
In the genesis of trembling hyperkinesis, hypersensitivity of central adrenergic receptors is of great importance, which entails a violation of control over peripheral mechanisms of regulation of muscle tension. Strengthening of sympathetic stimulation with the development of tremor is observed against the background of thyrotoxicosis, hypoglycemia. The same mechanism is activated in diseases of the adrenal glands - pheochromocytoma, Addison's disease.
The cause of damage to the nervous system in hyperparathyroidism is the deposition of calcium in the basal ganglia. Copper accumulates there in children with Hallervorden-Spatz and Wilson-Konovalov disease, which provokes neurodegeneration. In these cases, various types of tremor occur, including "flapping" (asterixis), which are combined with muscle rigidity, unsteadiness when walking, dysarthria. Progressive mental disorders, dementia. Wilson's disease is characterized by liver failure.
Hand tremor is observed with focal lesions of the cerebellum or brain stem. It is a low-frequency (3-5 Hz) large-scale trembling of the proximal limbs, which occurs at the beginning of the movement and intensifies as it approaches the target. Intentional terminal tremor can be supplemented by various types of postural. Such changes are provoked by the following pathologies of the central nervous system:
Tremor occurs immediately after stroke or after some time (weeks, months). When the midbrain is affected, it is accompanied by ataxia and other hyperkinesias, and when the pyramidal pathway is involved, it is accompanied by hemiparesis. A focus in the frontal lobe can lead to the development of an isolated writing tremor with rotational movements of the hand, and hemorrhages or tumors of the parieto-occipital region can lead to kinetic tremor.
Tremor manifests some hereditary diseases of the nervous system. Bilateral hand trembling at rest is characteristic of the syndrome of sensitive ataxia, neuropathy, dysarthria and ophthalmoplegia (SANDO). Symptoms are complemented by gait instability, oculomotor disorders, dementia. Fragile X-chromosome syndrome (FXTAS) patients have intentional hand tremor, cerebellar ataxia, and polyneuropathy.
For amyotrophy Kennedy, which has an X-linked recessive inheritance, tremor, convulsions during exercise, small fasciculations in the proximal limbs are typical. Muscle strength gradually decreases, they decrease in volume. Among the neurological symptoms, there are bulbar disorders (dysarthria, dysphagia), the picture is complemented by endocrine disorders - gynecomastia, testicular atrophy.
The peripheral mechanism of tremor formation is involved in polyneuropathies. The delay in the transmission of sensitive impulses from proprioreceptors first leads to excessive contraction of the antagonist muscles, and then is accompanied by oscillatory oscillations in both directions. Neuropathic hand tremor is usually postural-kinetic and occurs in a wide range of pathological conditions:
Toxic substances contribute to the activation of not only the peripheral mechanisms of tremor - the harmful effect is realized through damage to the neuronal structures of the extrapyramidal system. The basis of the pathological process is a violation of the generation and conduction of an impulse, a disorder of energy and plastic metabolism. The following compounds are neurotoxic:
Another mechanism for the development of tremor is observed in the withdrawal syndrome caused by the cessation of alcohol intake, the withdrawal syndrome of other psychoactive substances (opioids, tranquilizers). Trembling appears due to stimulation of the sympathetic nervous system, combined with vegetative-somatic and mental disorders. Many of these symptoms are similar to the post-toxic state.
Drug-induced hand tremor caused by medication is widely known. Some drugs can cause a dose-dependent increase in physiological tremor, which disappears after their withdrawal. The neurochemical mechanisms of tremor are associated with effects on the central cholinergic and monoaminergic or peripheral adrenergic systems. The following medicines have a side effect in the form of trembling:
A common pathology is neuroleptic parkinsonism, which occurs during treatment with antipsychotic drugs due to blockade of dopamine receptors in nigrostriatal structures. Metoclopramide, central sympatholytics (reserpine), serotonin reuptake inhibitors (fluoxetine) act in a similar way. In drug-induced parkinsonism, postural-kinetic tremor of the hands is noted, which increases relatively quickly, stops after discontinuation of the drugs.
It is possible to identify the cause of hand tremor based on the results of a comprehensive examination. At the initial stage, a neurologist correlates clinical symptoms with diagnostic criteria and makes a preliminary conclusion, but it is almost impossible to do without additional studies in determining the source of disorders. With tremulous hyperkinesis, the following procedures are recommended:
Some authors propose to investigate the time-frequency properties of EEG signals for diagnosing the early stages of Parkinson's disease. In case of endocrine pathology, ultrasound of the thyroid gland and adrenal glands is prescribed; it is possible to see the displacement of median structures during volumetric processes using echoencephalography. The doctor has to differentiate among themselves various diseases accompanied by tremor, and to distinguish it from other hyperkinesias.
The tactics of treating hand tremor is determined by its cause. Enhanced physiological trembling is stopped by the elimination of the provoking factor, but pathological variants require active therapy. Drug correction is predominantly symptomatic or pathogenetic. How to treat hand tremor in a particular case, the doctor determines. Based on the clinical situation, medicines of several groups are used:
To eliminate certain types of tremor, it is necessary to normalize endocrine-metabolic processes and eliminate infectious factors. In case of poisoning, intensive detoxification therapy is carried out with infusion solutions, sorbents, and antidotes. Physical methods of correction include the use of orthoses that limit hand movements, therapeutic exercises, and massage. In the early stages, fountain pens and cutlery with thick handles can minimize discomfort.
Patients with severe tremors that are difficult to respond to pharmacotherapy are offered surgical intervention. Stereotactic operations are indicated for focal pathology of the central nervous system, are represented by cryothalamotomy and other variants of destruction of the thalamic nuclei. Trembling can be suppressed by deep electrical stimulation of the basal ganglia. It is possible to eliminate the immediate cause of tremor by removing volumetric formations, eliminating the consequences of craniocerebral injuries.