Writer’s cramp: is focal dystonia the best explanation?

Abstract

Often considered no more than an historical curiosity, writer’s cramp remains an important disability in the workplace and the mechanism, which has puzzled the best medical minds for generations, remains contentious. A remarkable range of hypotheses has been put forward to try and explain a disability which periodically reached epidemic and economically worrying levels, but in the end medical opinion has accepted the explanation put forward by neurologists Sheehy and Marsden in 1983 that this was caused by a form of focal dystonia. However, the majority of the historical descriptions of writer’s cramp do not fit the classical parameters of focal dystonia and are more accurately described as a progressive forearm muscle fatigue. Today’s keyboard operators continue to complain of symptoms identical to their clerical forebears demonstrating that this is a problem which has evolved but not disappeared; this has the paradoxical advantage that modern research techniques enable this complaint to be revisited. The result shows that two varieties of writer’s cramp have always existed and while focal dystonia remains a valid explanation for a minority of cases, the much more common fatigue-based complaint is better explained by chronic compartment syndrome of the forearm.

A unifying motor control framework for task-specific dystonia

“…Changes in the presentation of patients with task-specific dystonia over the centuries highlight the importance of specific tools in the pathogenesis of task-specific dystonia5,45,46. In the 19 th century, the change from feather quills to steel nibs in scriveners and clerks was the cause of a dramatic increase in prevalence of occupational motor problems in the British Civil Service47. The new nibs altered the dynamics of the tool (and corresponding task kinematics) and writers did not have to stop periodically to sharpen steel nibs, which offered a brief rest from what would otherwise be a continuous task (predisposing to muscle fatigue)47,48.…”

“…In the 19 th century, the change from feather quills to steel nibs in scriveners and clerks was the cause of a dramatic increase in prevalence of occupational motor problems in the British Civil Service47. The new nibs altered the dynamics of the tool (and corresponding task kinematics) and writers did not have to stop periodically to sharpen steel nibs, which offered a brief rest from what would otherwise be a continuous task (predisposing to muscle fatigue)47,48. More than 10% of telegraph operators communicating in Morse code developed motor problems49.…”

“…Fatigue, overuse and injury are important risk factors for task-specific dystonia38,39,47. For example, facial injuries can precipitate motor impairments affecting the embouchure in wind and brass instrument players43,54.…”

“…Task-specific motor impairment can be divided into subtypes such as overuse injury, choking under pressure, dynamic stereotype and dystonia. Each subtype is likely to have differences of emphasis in both causative mechanisms and how they are encoded centrally43,47. For example, it has been suggested that dynamic stereotypes might represent an early modifiable form of motor impairment that can develop into dystonia if sufficient maintaining risk factors persist43.…”

Task specific dystonia – a patients’ perspective

“…24 ,25 Both depression and anxiety were within the top five most reported co-morbidities within our survey respondents. A few studies have indicated that there is an association with higher levels of anxiety 26 in patients who develop WD and traits of perfectionism, neuroticism, anxiety and phobias in musicians suffering with MD 27 Reported levels of anxiety and depression in the general adult UK population vary widely from 3.3% depression and 5.9% anxiety 28 to 19.7% 29 so it is difficult to make comparisons with our survey participants. The relationship between anxiety and depression and the development of TSD is an important area of future research.…”