Writer's cramp belongs to the group of focal dystonias and is distinguished by the presence of involuntary contraction of muscles responsible for finger, hand or arm movement, which may be repetitive and/or continuous. The term stems from the fact that contractions occur when writing, but they could also be seen when other tasks are performed. An abnormal hand posture and tremor are the main findings. The diagnosis rests on clinical criteria and exclusion of other possible etiologies.
The term writer's cramp represents one of the most widely recognized focal dystonias in clinical practice, with approximately 3-7 cases per 100,000 individuals   . It is defined as a task-specific motor abnormality of the hand characterized by involuntary and either sustained or persistent contractions of muscle groups that are needed for the task of writing to be carried out    . Because of these contractions, the arm, hand, or finger are in an abnormal posture (thus preventing the individual from performing this task), which is the principal component of the clinical presentation     . In addition to abnormal posturing, patients complain of tremor during writing, use of excessive force to hold the pen, but also pain and significant discomfort   . Abnormal hand posture, joint, and muscle cramping has been confirmed in patients when performing other manual tasks as well, and the term complex writer's cramp is used to describe this clinical entity . Some studies have documented the surprisingly common presence of a "mirror dystonia" - muscle spasms of the opposite hand during the physical examination . Furthermore, some reports have stressed the role of writer's cramp impeding professional work, whereas others found significantly higher rates of anxiety disorders and depression in this patient population   , indicating that the burden of this seemingly benign condition on the quality of life may be much greater than anticipated.
The diagnosis of a writer's cramp is primarily based on clinical findings (as the exact etiology remains unknown in the majority of cases)   , which is why the role of a properly obtained patient history and a detailed physical examination is essential. Physicians must assess the circumstances that precede the appearance of involuntary muscle contractions (prolonged repetitive movements seen in writing, hence the term writer's cramp) , as well as their duration and severity and other associated symptoms. Because the disorder appears almost always when performing the specific task of writing, patients should be asked to write during the physical examination in order to confirm the disorder. The wide differential diagnosis of tremor and dystonia, however, necessitates a more thorough laboratory and imaging workup. In addition to a detailed family history that may reveal similar illnesses in close family members, imaging studies of the endocranium and electrophysiology testing are recommended. Typical findings on electromyography (EMG) are co-contraction of both the agonist and antagonist muscles of the hand and forearm .