Dystonic Tremor: Time to Change.

BACKGROUND: The term dystonic tremor is being increasingly used in neurological publications despite uncertainties about its meaning. We provide here a historical reconstruction from its original introduction in 1984 to help distinguish dystonia from essential tremor. METHODS: A comprehensive Pubmed search of MeSH terms "dystonia", "tremor", and "essential tremor" provided the information base for reconstructing historical usage of the term "dystonic tremor". RESULTS: Over the years, this expression was enriched of additional meanings and sided by companion descriptors, such as tremor associated with dystonia. Dystonic tremor has been considered characteristically coarse, jerky, irregular, directional and asymmetrical. These characteristics, however, are not included in the most recent definitions of tremor. The relationship between tremor and dystonia is not easy to untangle, as the two phenomena are often recognized in association. Tremor and dystonia experts have developed different visions of dystonic tremor that have been variably implemented. There are currently two independent consensus definitions, which are not coincident and imply different pathophysiological interpretations. CONCLUSIONS: This historical reappraisal highlights that usage of the expression dystonic tremor has evolved over time to lose its original meaning. Notwithstanding inconsistencies of current definitions, its usage has steadily increased and it is time now to agree on an updated terminology.

The evolving definition of essential tremor: What are we dealing with?

BACKGROUND: Although essential tremor (ET) is commonly encountered in clinical practice, historically, there has been considerable disagreement as how to best define it, and now with a growing sense of its clinical complexity, how to best encapsulate it. Here, I draw attention to five issues of current uncertainty. METHODS: A PubMed search conducted on June 19, 2017 crossed "essential tremor" with 9 second search terms (e.g., definition, diagnosis). RESULTS: There are several major issues of clinical and diagnostic uncertainty. Underlying each issue is a larger question about the nature of the underlying pathophysiology of ET. Does age of onset of ET matter? How much dystonia is acceptable in ET? How much in the way of "cerebellar signs" are acceptable? Are non-motor features due to the underlying disease or merely secondary to the clinical features? Is ET a single disease entity or something else? CONCLUSIONS: We are learning more about ET and, as a by-product of these efforts, are struggling with its definition. Further understanding the nature of the underlying disease pathogenesis as well as the role the cerebellum and cerebellar relays play in this process will likely provide important clues to enable us to bring order to areas of uncertainty.

De Sedibus et Causis Morborum: is Essential Tremor a Primary Disease of the Cerebellum?

Morgagni's 1761 publication of De sedibus et causis morborum (i.e., of the Seats and Causes of Diseases) represented a paradigmatic moment in the history of medicine. The book ushered in a new way of conceptualizing human disease, shattering old dogma, and linking constellations of symptoms and signs (i.e., clinical disease) with anatomic pathology in specific organs (i.e., organ disease). This was the anatomical-clinical method, and it attempted to unveil "the seat" of each disease in a specific organ. Essential tremor (ET) is among the most common neurological diseases. There is little debate that the origin of ET lies in the brain, but if one tries to delve more deeply than this, things become murky. The dogma for the past 40 years has been that the seat of ET is the inferior olivary nucleus. Closer scrutiny of this model, however, has revealed its many flaws, and the model, based on little if any empiric evidence, has increasingly lost favor. Arising from a wealth of research in recent years is a growing body of knowledge that links ET to a disarrangement of the cerebellum. Data from a variety of sources reviewed in this issue (clinical, neuroimaging, neurochemical, animal model, physiological, and pathological) link ET to the cerebellum. That the cerebellum is involved in an abnormal brain loop that is responsible for ET is not debated. The tantalizing question is whether an abnormality in the cerebellum is the prime mover, and whether the cerebellum is the seat of this particular disease.

Essential tremor.

Essential tremor (ET) is among the most common neurological disorders. This chapter reviews the epidemiology, clinical features, and pathophysiology of ET. The defining feature is a kinetic tremor of the arms. Patients often have a postural tremor as well. Other body regions may also be involved (especially the head). The severity of tremor may range from mild cases in population settings to more severe cases in treatment settings. Motor features aside from tremor have been described in ET, including tandem gait difficulty. Mild cognitive changes (especially executive dysfunction) have been documented in many studies as well. Despite being regarded as one of the most common hyperkinetic movement disorders, establishing a precise prevalence has been difficult, yet the prevalence among persons aged 40 and older seems to be 4% or higher. There are numerous examples of families in which the disease appears to be inherited yet genetic studies have not progressed to the point where ET genes have been identified. There is also a growing understanding that environmental factors are likely to contribute to the etiology of ET. More recent postmortem studies have helped localize the possible source of ET to structural alterations in the cerebellum and its connecting pathways.

Historical underpinnings of the term essential tremor in the late 19th century.

BACKGROUND: The term essential tremor has been in regular use since the second half of the 20th century. To modern neurologists, the word "essential" may seem cryptic. The historical underpinnings of this term have not been examined. OBJECTIVES: To bring to attention early medical reports using the term essential tremor and examine the characteristics of the disorder that contributed to the proposed use of the term. METHODS: Review of 19th and early 20th century medical literature on essential tremor. RESULTS: The term tremore semplice essenziale (simple essential tremor) was first used by Burresi (Italy, 1874) to describe an 18-year-old man with severe, isolated action tremor. Several years later, Maragliano (Italy, 1879), Nagy (Austria, 1890), and Raymond (France, 1892) described similar cases and proposed the terms tremore essenziale congenito (essential congenital tremor), essentieller Tremor (essential tremor), and tremblement essentiel héréditaire (hereditary essential tremor) to define the illness. Mirroring contemporaneous views of constitutional and inherited disease, the key ingredients of the disorder were viewed as the constant presence of tremor in the absence of other neurologic signs and its heritable nature. By the early 20th century, the term began to appear in the medical literature with greater frequency. CONCLUSIONS: Toward the end of the 19th century, several clinicians attempted to provide a nosologic separation for a tremor diathesis that was often familial and occurred in isolation of other neurologic signs. This disorder, which was termed essential tremor, was later recognized as one of the most common neurologic disorders.

Silas Weir Mitchell's essential tremor.

Silas Weir Mitchell (1829-1914) is recognized as an important American neurologist. Biographers refer in brief to a tremor. The objective of this review was to characterize Mitchell's tremor using handwriting samples, to examine handwriting samples of family members to determine whether this tremor was familial, and study Mitchell's allusions to tremor in personal, scientific, and fictional writings. Primary sources were the Papers of S. Weir Mitchell, College of Physicians of Philadelphia, and Mitchell's scientific and fictional writings. Mitchell's early handwriting was tremor-free yet, by 1873, the writing was tremulous. Handwriting in the 1880s and 1890s shows clear oscillations of moderate-amplitude. By the first decade of the 20th century, his handwriting was virtually illegible. Letters written by two siblings, his mother, and maternal grandfather also reveal tremor. Tremor was not prominent in Mitchell's personal or scientific writings and Mitchell referred to tremor in only 4 of 27 fictional writings. In conclusion, Mitchell had a familial action tremor that began when he was in his early 40's and worsened considerably with age. The likely diagnosis was essential tremor. Curiously, Mitchell rarely alluded to tremor in personal writings and tremor was not prominently featured in his scientific or fictional works.

John Adams' essential tremor.

John Adams (1735-1826), one of the signers of the Declaration of Independence, was the second President of the United States. Adams had tremor for many years, about which little has been written. We examined John Adams' penmanship over a 62-year period and studied his correspondence and diaries. It is not clear when Adams' tremor began, although in a diary entry dated 6 December 1760, when Adams was 25 years old, there is evidence of low-amplitude kinetic tremor. The tremor continued in his written correspondence, becoming more persistent over time. Later in life, the clarity of his written correspondence diminished, with greater decomposition of characters and a reduction in the size of individual characters. This finding raises some speculation as to whether Adams could have been developing some parkinsonism, although the evidence in favor of this is not compelling. The most likely diagnosis was essential tremor.

Illnesses of the brain in John Quincy Adams.

John Quincy Adams, the sixth and perhaps most scholarly American president, served courageously despite familial essential tremor, depression, and cerebrovascular disease. His cousin Samuel Adams and his father John Adams also had essential tremor, which the later called "quiveration". Alcoholism and depression affected several members of J.Q. Adams's family. Following his own time as president, J.Q. Adams returned to duty as the congressman who most assiduously fought slavery, a fight he continued even after he had suffered a major left hemispheric stroke. His fatal collapse in Congress, protesting the Mexican War, is legendary among the final illnesses of American statesmen.