Essential tremor

Claudia M Testa MD PhD (Dr. Testa of Virginia Commonwealth University received research grants from Auspex and Teva.)
Joseph Jankovic MD, editor. (Dr. Jankovic, Director of the Parkinson's Disease Center and Movement Disorders Clinic at Baylor College of Medicine, received research funding from Allergan, Allon, Ceregene, Chelsea, EMD Serono, Impax, Ipsen, Lundbeck, Medtronic, Merz, and Teva, and compensation for his services as a consultant or an advisory committee member by Allergan, Auspex, EMD Serono, Lundbeck, Merz, Neurocrine Biosciences, and Teva.)
Originally released October 4, 1993; last updated September 30, 2016; expires September 30, 2019

This article includes discussion of essential tremor, benign essential tremor, benign tremor, familial tremor, and heredofamilial tremor. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

Essential tremor is the most common movement disorder in adults. Many people with essential tremor have not been diagnosed by a physician even though many report functional disability. This article discusses the clinical presentation, differential diagnosis, pathophysiology, and treatment of essential tremor. Publications pertaining to the diagnosis, genetics, and treatment of essential tremor are reviewed. There is an ongoing effort to update the classification of tremor, which may impact essential tremor clinical diagnosis. Unfortunately, available medications are frequently inadequate, and work on new therapeutics is limited. Thalamic deep brain stimulation is effective in most patients, and new stereotactic surgical sites are being explored. New surgical techniques are under active investigation. There is considerable evidence that essential tremor is a clinically defined tremor syndrome with multiple etiologies; this probably explains much of the difficulty in identifying underlying causes and developing new treatments.

Key points

 

• Classic essential tremor is a primary tremor syndrome.

 

• The extent of nontremor symptoms possible within essential tremor is disputed but at least includes mild changes in balance, and in some patients, mood and cognitive changes.

 

Parkinson disease, dystonia and other tremorogenic conditions are frequently misdiagnosed as essential tremor.

 

• Abnormal oscillation in the cerebellothalamocortical pathway likely produces tremor, but the structural, biochemical, and genetic mechanisms of essential tremor are uncertain.

 

• There is slow growth in tremor treatment options. Pharmacotherapeutic options (eg, primidone and propranolol) are limited and vary in efficacy. Occupational therapy and mechanical nonmedication interventions, such as specialized utensils, are increasing in variety and utility. Deep brain stimulation and unilateral standard and focused ultrasound thalamotomy surgeries are effective therapeutic options for patients with disabling tremor that responds inadequately to other interventions.

 

• Treatments focusing on nonmotor areas such as psychosocial coping, anxiety, and depression can improve overall quality of life as well as tremor treatment.

Historical note and terminology

Tremor is an involuntary rhythmic oscillatory movement of any body area (Jankovic and Fahn 1980; Deuschl et al 1998). Some level of involuntary oscillation, called physiologic tremor, is normal. At the other end of the spectrum, pathologic states produce involuntary oscillations ranging from mild to disabling. Tremor is the most common neurologic movement disorder. Tremor is categorized as rest, postural, or kinetic tremor according to whether the tremor occurs in repose, steady posture, or movement. Descriptions of tremor date back centuries, to Ecclesiastes XII:3 and ancient India and Egypt (Louis 2000). The specific distinction of kinetic tremor can be found in Galen's writings (Sider and McVaugh 1979) and many accounts since (Louis 2000). Historically, the distinction between action tremor (postural tremor or kinetic tremor) and rest tremor was a seminal event in distinguishing essential tremor from Parkinson disease (Koehler and Keyser 1997). The term “essential tremor” was developed in the 1800s to describe an isolated action, often familial, tremor (Louis et al 2008a).

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