Tremors: Causes, Types, Categories, Treatment, Surgery
Tremor is a rhythmic muscle movement, which is unintentional and comprises of back and forth movements (oscillations) of a part or more than one part of the body.1 There are many involuntary movements of the body of which tremors are the most common and can affect the arms, hands, head, voice, face, trunk and legs. Hands are more commonly affected by tremors. Sometimes, tremor can be an indication of an underlying neurological disorder or it can also occur as a side effect of some medicines. The commonest type of tremor; however, tends to occur in otherwise healthy individuals.
Tremor is not a life-threatening problem; however, it can be embarrassing for some people who can also find it difficult to perform day to day activities.
Treatment for tremor comprises of treating the underlying cause, medications and surgery.
Causes of Tremor
- Any type of problem in the regions of the brain, which control the muscles of the entire body or in certain areas, such as the hands causes tremor.
- Some of the neurological disorders and other medical conditions, which cause tremors, include stroke, multiple sclerosis, traumatic brain injury, and neurodegenerative diseases, which destroy or damage areas of the cerebellum or the brainstem.
- Use of certain drugs, such as corticosteroids, amphetamines, certain psychiatric medications, alcohol withdrawal or abuse, overactive thyroid, mercury poisoning or liver failure can also cause tremors.
- There are some types of tremors, which have no known cause; whereas some types of tremors are inherited and tend to run in the family.
Characteristics of Tremor
- Patient experiences rhythmic shaking in the arms, hands, head, legs or trunk.
- Patient can have a shaky voice.
- Patient experiences difficulty in writing or drawing.
- Patient will also have trouble with holding or controlling utensils, such as a spoon, fork or knife.
- Strong emotion or stress can trigger or exaggerate some form of tremors.
- Tremors are also triggered when a person is exhausted physically.
- Certain movements or postures can also start tremors.
- Tremor can affect anyone of any age; however, it commonly affects middle-aged and older individuals.
- Tremor can be an occasional occurrence or a temporary one, or it can occur intermittently.
- Men and women both are equally affected by tremors.
Types of Tremors
A better method of understanding and describing tremors can be done by defining them according to their types.
- Resting tremor is a tremor which occurs when the muscle is relaxed, e.g. when the hands are resting on the lap. This tremor can be described as a shaking of the limb, even when the patient is not moving and is at rest. Resting tremor often affects only the hand or the fingers. This tremor is commonly seen in patients suffering from Parkinson's disease.2
- An action tremor is that tremor which occurs during any movement in the affected body part. There are many sub-classifications of an action tremor.
- Kinetic tremor is that tremor which occurs during movement of a particular body part, e.g. moving the wrists up and down.
- Postural tremor occurs when the patient is maintaining a position against gravity, e.g. holding the arms outstretched.
- Intention tremor occurs during a purposeful movement towards a particular target, e.g. touching the finger to one's nose.
- Isometric tremor is that tremor which occurs during a voluntary muscle contraction, which is not accompanied by any movement. Task-specific tremor occurs when doing goal-oriented, highly skilled tasks like speaking or handwriting.
Different Categories of Tremor
Classification of tremor is done based on its cause or origin and its appearance. Given below are some of the commonly occurring tremors along with their symptoms:
Essential Tremor, also known as benign essential tremor, is the most common type of abnormal tremor.3 In some people, this tremor is non-progressive and mild for over a lengthy period of time; whereas in other individuals, this tremor is slowly progressive, beginning on one side of the body and slowly affecting both the sides in a few years. This type of tremor commonly affects the hands first, but the voice, head, tongue, trunk and legs can also be affected; however, the extent of it is less than that of the hands. The hand tremor often presents as an action tremor. The head tremor can occur as a “yes-yes” or “no-no” movements. There may be mild gait disturbance along with the essential tremor. The frequency of the tremor can decrease with a person’s age, however, the severity of it can increase which can affects person's quality of life and the ability to perform daily tasks of living. Increased emotion, fever, stress, physical exertion, or low blood sugar can also trigger tremors and/or increase the severity. The onset of this tremor more commonly occurs after 40 years of age, but the symptoms can start at any age. More than one family member can be affected by this tremor.
According to research, individuals with essential tremor also suffer from mild degeneration of some specific areas of the cerebellum.
Parkinsonian Tremor occurs as a result of damage to structures present inside the brain, which help in controlling movement. The main characteristic of Parkinsonian tremor is that it is commonly seen as a resting tremor. It can be an isolated symptom or can be seen with other disorders. Tremor is usually the first symptom of Parkinson's disease. There is “pill-rolling” action of the hands which is the classic sign of this tremor and can also affect the lips, chin, trunk and legs and is exaggerated by increased emotions and stress. The parkinsonian tremor starts usually after the age of 60. The movement begins on one side of the body or in one limb and commonly progresses to the other side.
Cerebellar Tremor occurs in the extremities and is a slow tremor which occurs at the end of any intentional movement, such as touching a finger to the tip of the nose or trying to press a button. Damage to the cerebellum or lesions in the cerebellum occurring from tumor, stroke, diseases, such as multiple sclerosis or some other inherited degenerative disorder causes cerebellar tremor. Medicine overuse and chronic alcoholism can also cause cerebellar tremor. In a classic cerebellar tremor, there is a lesion on one side of the brain which produces tremor on that same side of the body. Directed movement worsens this tremor. A “wing-beating” type of tremor known as the Holmes' tremor or rubral tremor occurs from cerebellar damage. Cerebellar tremor is most obvious when the affected person is holding a particular posture or is very active. Other problems can also occur with cerebellar tremor, such as nystagmus, dysarthria gait problems, and postural tremor of the neck and trunk.
Dystonic Tremor is seen in individuals from different ages who have dystonia, which is a movement disorder comprising of sustained involuntary muscle contractions resulting in repetitive motions, twisting and/or abnormal and painful postures/positions, such as torticollis (twisting of the neck) or writer's cramp. Any muscle of the body can be affected by dystonic tremor and is commonly seen when the patient moves in a certain way or is in a certain position. The dystonic tremor can be different than the essential tremor. Dystonic tremors tend to occur irregularly and complete rest commonly alleviates it. The severity of the tremor can also be reduced by touching the affected muscle or body part. The tremor can be the initial symptom of dystonia which is localized to a specific part of the body.
Psychogenic Tremor (Functional Tremor) can occur as any type of tremor movement. The characteristics of psychogenic tremor can be different, but often occurs as a sudden onset and remission. This tremor worsens with stress, any change in the direction of the tremor and/or the affected body part. This tremor decreases or disappears when the person is distracted. Conversion disorder also affects many individuals who have psychogenic tremor. Conversion disorder is a psychological condition which produces physical symptoms.
Physiologic Tremor is seen in every normal person. It is very rarely seen by the eye and this tremor is exaggerated by strong emotions such as fear, anxiety or physical exhaustion, hyperthyroidism, hypoglycemia, stimulants, heavy metal poisoning, caffeine, alcohol withdrawal or fever. Physiologic tremor can occur in all the voluntary muscle groups. This tremor can be detected by extending the arms and keeping a piece of paper on the hands. Once the cause is treated, this tremor is often reversible.
Orthostatic Tremor is a tremor which is characterized by rhythmic muscle contractions that occur in the trunk and legs immediately after standing up. Orthostatic tremor is usually perceived as unsteadiness than an actual tremor. The frequency of the tremor is high due to which it cannot be seen, but can be heard sometimes through stethoscope applied to the thigh muscles. Patient does not have any other clinical signs or symptoms and the tremor or the unsteadiness subsides when an individual sits down, starts walking or is lifted off the ground.
Investigations for Tremor
- A physical exam is conducted during which the doctor will determine whether the tremor is occurring during rest or movement.
- The symmetry of the tremor is also checked along with any sensory loss, weakness or atrophy of the muscle or decreased reflexes.
- A detailed family history is taken to find out if the tremor is inherited.
- Blood tests and urine tests are done to find out any thyroid malfunction, abnormal levels of some chemicals or other metabolic causes of the tremor.
- The above tests also help in identifying any contributing causes, such as chronic alcoholism, drug interaction, or some other disease or condition.
- Diagnostic imaging, such as computerized tomography (CT) scan or magnetic resonance imaging (MRI) is done to determine if there is any structural defect or brain degeneration causing the tremor.
- A neurological examination is conducted to assess nerve function along with motor and sensory skills. These tests help in determining any functional limitations, like difficulty with handwriting or difficulty in holding a cup or other utensil.
- Electromyogram (EMG) is done to diagnose any nerve or muscle problems. The involuntary activity of the muscle and its response to nerve stimulation is measured with this test.
Treatment for Tremor
- Most of the tremors have no cure. Treatment depends on the diagnosis of the cause.
- Treating the underlying condition helps in relieving some of the tremors. Such as in the case of psychogenic tremor, if the underlying psychological problem is treated then the tremor also subsides.
- There are many symptomatic medicines available for different types of tremor. Medicines for Parkinsonian tremor include levodopa and/or dopamine-like drugs, such as ropinirole and pramipexole . There are other drugs available, which help in reducing the severity of the Parkinsonian tremor, such as anticholinergic drugs and amantadine hydrochloride.
- Cerebellar tremor often does not respond well to medical treatment.
- Essential tremor can be treated with beta blockers, such as propranolol and nadolol.
- Primidone is an anticonvulsant drug which is also beneficial in essential tremor.
- Dystonic tremor can respond to medicines, such as anticholinergic drugs, clonazepam, and intramuscular (I.M.) injections of botulinum toxin. Tremors of the voice and head and various movement disorders can also be treated with Botulinum toxin.
- Primidone and clonazepam can also be given for primary orthostatic tremor.
- It is important to eliminate tremor "triggers" such as alcohol, caffeine and other stimulants from the diet.
- Enhanced physiologic tremor is often reversible if the cause is corrected. Beta blockers can be used as symptomatic treatment.
- Physical therapy can help in reducing the tremor and in enhancing the coordination and muscle control of some individuals. The physical therapist will assess the individual for muscle control, tremor positioning, muscle strength, and other functional skills. The patient is taught to brace the involved limb during the tremor or to hold the involved arm close to the body. This will help in gaining motion control.
- Balancing and coordination exercises are also beneficial in some cases. Using splints, weights and other adaptive equipment, such as special plates or utensils to help with eating, can also be done.
Surgery For Treating Tremors
Surgical procedures, such as deep brain stimulation and thalamotomy help in easing certain tremors. These surgeries are commonly done if the tremor is severe and cannot be alleviated or controlled with medicines.
Deep brain stimulation (DBS) is the most common type of surgical treatment for tremor. This procedure comprises of using implantable electrodes for sending high-frequency electrical signals to the thalamus. There is a battery-operated device known as neurostimulator, which is used for delivering electrical stimulation to targeted region in the brain, which are responsible for controlling movement. A hand-held magnet is used to turn on and turn off the pulse generator which is surgically implanted beneath the skin. The electrical stimulation helps in temporarily disabling the tremor and in reversing the tremor. The life of the batteries present in the generator is about 5 years and can be surgically replaced. Deep brain stimulation is presently used in treating essential tremor, parkinsonian tremor and dystonia.
Thalamotomy is a procedure where lesions are created in the thalamus. This treatment is quite effective in treating cerebellar tremor, essential or Parkinsonian tremor. This procedure is done under local anesthesia and the patient is awake during this procedure. The patient’s head is secured in a metal frame. Then the surgeon maps the brain to isolate the thalamus. There is a small hole drilled through the skull and an electrode, which is temperature-controlled, is inserted into the thalamus. Next, a low-frequency current is then passed through this electrode for activating the tremor and confirming the proper placement of the electrode. After the site has been confirmed, there is heat passed though the electrode to create a temporary lesion. The patient is then tested for language, speech, coordination, and tremor activation, if present. If there are no problems, then electrode is heated again to create a permanent lesion, which is 3 mm in size. After the electrode is cooled to body temperature, it is withdrawn and the skull hole is covered afterwards. The creation of this lesion results in permanent disappearance of the tremor without affecting the motor or sensory control.
The common side effects of surgery for tremor include:
- Dysarthria, which are problems with the motor control of the speech.
- Temporary or permanent cognitive impairment, which includes learning and visual difficulties.
- Problems with balance and coordination.