Dr. Jankovic, Director of the Parkinson's Disease Center and Movement Disorders Clinic at Baylor College of Medicine, has received research and/or training grants from Adamas, Allergan, Biotie, Civitas/Acorda, Hoffmann-La Roche, Medtronic, Merz, Neurocrine , Nuvelution, Pfizer, Prothena, Psyadon, Revance, and Teva; and has served as a consultant or as an advisory committee member for Adamas, Allergan, Merz, Prothena, Revance, and Teva.)
In this article, the author reviews new studies related to the pathogenesis of essential tremor, including Purkinje cell pathology as well as LINGO1 and SLC1A2 genes. Clinical diagnosis of tremor disorders and treatment strategies for essential tremor are described in detail.
• Two subtypes of essential tremor pathology have been identified: a primarily cerebellar variant with Bergmann gliosis and Purkinje cell torpedoes, and a Lewy body variant.
• Propranolol and primidone are useful first-line medications for essential tremor.
• Deep brain stimulation surgery continues to be useful for severe, medication-resistant tremor.
Historical note and terminology
The history of tremor can be roughly divided into 2 phases. The first and largely descriptive phase began in the 19th century; clinicians were able to recognize the principal manifestations of tremor and characterize and classify different forms of tremor based on clinical patterns and their relationships with known pathologies. GF Most provided 1 of these reports of action tremor in 1836. The first known use of the term “essential tremor” was traced to Pietro Burresi in 1874 (Louis 2008). The names of Romberg, Parkinson, Gowers, and Charcot all contributed extensively to our knowledge and laid the groundwork for the second phase. Charcot collected handwriting samples from his patients and differentiated between tremulous handwriting in essential tremor and micrographic handwriting in Parkinson disease (Goetz 2007). Gowers described rest tremor at the metacarpal-phalangeal joints as someone beating a small drum (Goetz 2007).
The second phase began in the latter part of this century with the explosion of newer technologies that were able to further identify the pathophysiology of tremor. This explosion also contributed to our further ability to carefully classify clinical syndromes not only in terms of their phenomenology and pathology but also their neurophysiology. This phase has led to significant improvements and advances in treatment culminating presently with surgical therapies and deep brain stimulation.
Descriptions of the contributions of early American investigators to the understanding of tremors (Lanska 2000), and documentation of essential tremor in Samuel Adams, an early American patriot (Louis 2001c), provide an interesting historical perspective on tremor.
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