Tremor overview

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Epidemiology and Demographics
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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 unintentional, somewhat rhythmic, muscle movement involving to-and-fro movements (oscillations) of one or more parts of the body. It is the most common of all involuntary movements and can affect the hands, arms, head, face, vocal cords, trunk, and legs. Most tremors occur in the hands. In some people, tremor is a symptom of another neurological disorder. The most common form of tremor, however, occurs in otherwise healthy people.

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.

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%.

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.

Diagnosis

Diagnostic Study of Choice

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.

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.