Tremor overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Zehra Malik, M.B.B.S[2]
Overview
Tremor is an involuntary, rhythmic, oscillatory movement, it is the most common involuntary movement disorder. Essential tremor, Parkinson's disease and enhanced physiologic tremor are the common causes of tremor to present in a primary care setting. Essential tremor is the most common. Other causes are caffeine intake, excessive alcohol, hypoglycemia, stress, anxiety, depression, fatigue, Wilson's disease, hyperthyroidism, multiple sclerosis, normal aging. Tremor can be classified into resting and action. Action tremor is further divided into postural, kinetic (simple or intentional), isometric and task-specific tremor. It is thought that tremor is the result of a combination of different mechanisms that could result in oscillatory/rhythmic movement. These mechanisms are mechanical oscillations, reflex oscillations, central oscillations, and cerebellar oscillation. Tremor must be differentiated from diseases that cause involuntary movement: myoclonus, clonus, asterixis, and epilepsia partialis continua. Essential tremor and Parkinson's disease worsens with time, treatment helps minimizing symptoms. Physiologic tremor does not worsen with age.
Historical Perspective
- James Parkinson, identified the tremor as "involuntary tremulous motion in parts not in action," in his essay on the shaking palsy, in 1817.
- Orthostatic tremor was first described by Kenneth M Heilman in 1984.
- Pietro Burresi in 1874, used the term essential tremor.
Classification
Tremor may be classified into:
- Resting or Action tremor.
- Action tremor further includes postural, kinetic (simple or intentional), isometric and task-specific tremor.
Pathophysiology
- It is thought that tremor is the result of a combination of different mechanisms that could result in oscillatory/rhythmic movement.
- These mechanisms are mechanical oscillations, reflex oscillations, central oscillations, and cerebellar oscillation.
- These mechanisms differ on the basis of their origin.
- Mechanical oscillations occurs in limbs, could be limited to a particular joint.
- Reflex oscillations originates from afferent muscle spindles
- Central neuronal pacemaker involves thalamus, basal ganglia, inferior olive.
- Cerebellar oscillations are due to disturbances in feedforward or feedback loops in cerebellum.
Causes
- Common causes of tremor in primary care include enhanced physiologic tremor, essential tremor, and Parkinson’s disease.
- Other causes are caffeine intake, excessive alcohol, hypoglycemia, stress, anxiety, depression, fatigue, Wilson's disease, hyperthyroidism, multiple sclerosis, normal aging.
Differentiating Tremor from other Diseases
- Tremor must be differentiated from diseases that cause involuntary movement: myoclonus, clonus, asterixis, and epilepsia partialis continua.
- The cause of tremor must also be differentiated from other conditions that cause tremor: essential tremor, physiological tremor, Parkinson's disease, cerebellar tremor, orthostatic tremor.
Epidemiology and Demographics
- The incidence and prevalence of tremor as a symptom is not determined.
- The incidence of essential tremor increases with age, it has bimodal incidence according to age. The prevalence of essential tremor is approximately 0.4% to 5.6%.
- The incidence of Parkinson's disease is in the range of 8 to 18 per 100,000 people yearly, seven million people worldwide and one million people in the United States are suffering from Parkinson's disease.Parkinson's disease is higher in Caucasians as compared to black or oriental population. Parkinson's disease is more common in rural population.
Risk Factors
Common risk factors include:
- Essential Tremor: Family history, over forty age
- Parkinson's Disease: Caucasian, male gender
- Physiologic Tremor: Caffeine, stress, muscle fatigue, low blood sugar, anxiety
Screening
- There is insufficient evidence to recommend routine screening for tremor.
Natural History, Complications and Prognosis
- Essential tremor and Parkinson's disease worsens with time, treatment helps minimizing symptoms.
- Physiologic tremor and drug induced tremor do not worsen with time and can be controlled.
- Tremors may be mild, or can be very disabling for some patients.
- Patients with tremors have shown to have decrease quality of life physically and mentally as compared to healthy population.
Diagnosis
Diagnostic Study of Choice
- Tremor is primarily diagnosed based on the clinical presentation. Diagnosing the underlying etiology of tremor is also a clinical diagnosis based upon, detailed history taking, observing patients as they enter the room and during history taking, followed by a focused physical exam.
History and Symptoms
- Tremor is the most common involuntary movement disorder. in the primary care setting the most common causes of tremors are essential tremors, Parkinson's disease and enhanced physiologic tremor.
- Important features of tremor in patients history are: mode of onset, unilateral or bilateral tremor, type of tremor (resting or action), symmetric or asymmetric, associated signs and symptoms, aggravating and relieving factors, medications, family history.
Physical Examination
Laboratory Findings
- Tremor is more of a clinical diagnosis. However, some causes of tremors can be identified through laboratory workup, hyperthyroidism, hypoglycemia, hepatic malfunction, renal impairment, Wilsons disease.
Electrocardiogram
- Tremor can mimic ventricular tachycardia on ECG appearing as a broad QRS complex and cause an artifact. It must be differentiated by finding normal QRS complexes hidden between artifact waves and looking for unstable baseline at the beginning of the ECG recording.
- Hyperthyroidism can appear as sinus tachycardia, atrial flutter or atrial fibrillation on ECG.
- Stress and anxiety can cause sinus tachycardia on ECG.
- It is important to obtain an ECG in patients diagnosed with tremor before starting medications like propranolol to investigate for bradycardia.
X-ray
- There are no x-ray findings associated with tremor.
Echocardiography and Ultrasound
- There are no echocardiography findings associated with tremor. Magnetic resonance-guided focused ultrasound (MRgFUS), is a noninvasive focused ultrasound ablative thalamotomy procedure used to treat essential tremor.
CT
- Neuroimaging using CT scan may help determine if the tremor is the result of a structural defect or degeneration of the brain.
- CT scan can be used to diagnoses cerebellar cause of tremor or can identify stroke, multiple sclerosis, Wilsons disease.
- SPECT of the nigrostriatal dopaminergic system can help distinguish essential and dystonic tremors in Parkinson's disease from neurodegenerative Parkinson's disease.
MRI
- An MRI is not helpful in diagnosing most common causes of tremor, it can help diagnose some less common causes of tremor including, cerebellar lesion, stroke, multiple sclerosis , Wilsons disease.
- It may help determine if the tremor is the result of a structural defect or degeneration of the brain.
- Magnetic resonance guided focused ultrasound (MRgFUS), is a noninvasive focused ultrasound ablative thalamotomy procedure used to treat essential tremor.
Treatment
Medical Therapy
- Non-pharmacological Therapy: Lifestyle changes, physical therapy, psychological techniques (relaxation, biofeedback).
- Pharmacological Therapy:
- Essential tremor: First line medications are propranolol (40 to 240 mg/day) or primidone.
- Parkinson's disease: First-line, Carbidopa-levodopa in combination, as carbidopa prevents conversion of levodopa into dopamine before reaching the brain, hence increasing efficacy.
- Physiologic Tremor: Factors than enhance a physiological tremor must be controlled. Propranolol can be take prophylactically to prevent enhanced physiologic tremor in situations that trigger it.
- Multiple Sclerosis: Beta-blockers, anxiolytics, anticonvulsants can help minimize MS-related tremors.
- Orthostatic Tremor: First line medication is clonazepam, should be started at 0.5mg and titrated up to 2mg thrice a day.
- Alcohol withdrawal tremor: Hydration, folate, thiamine, multivitamin, benzodiazepine.
Surgery
- Surgery is not first line treatment for any cause of tremor.
- It is opted for once non-pharmacological and pharmacological therapy fails.
- Interventional procedures used to treat tremors include:
- Botulinum neurotoxin injections
- Thalamotomy,
- Deep brain stimulation
- Magnetic resonance-guided focused ultrasound
- Radio-surgical gamma knife thalamotomy