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Keywords:

  • Writer's cramp;
  • Liability to pressure palsy;
  • Cocontraction;
  • Preserved motor abilities;
  • Motor program error

Abstract

A 49-year-old man reported several periods of acute paresis of different nerves after exposure to pressure. All palsies showed a good recovery over a period of days to months. The suspected diagnosis of a hereditary neuropathy with liability to pressure palsies was confirmed by the histology of a suralis nerve biopsy, which showed a distinct tomaculous swelling of the myelin. Nine years ago he noticed an acute, distally pronounced palsy of the right arm. A brachial plexus lesion was diagnosed. His profession required written work, thereby forcing him to compensate this weakness by increasign the coactivation of the elbow and upper arm. This coactivation persisted even after complete recovery from the plexus palsy. Thus, the patient showed the typical feature of classcal writer's cramp, with broad coactivation of the arm muscles, which has continued to the present. At the same time, however, the patient was able to perform other motoric tasks well, such as painting. After several practice sessions with a special program that makes use of preserved motor abilities to reestablish writing, the patient was again able to write with a normal kinematic profile as documented by the recorded handwriting. This suggests that the “writer's cramp” of our patient is one form of task-related dystonia that may be related more to the perserveration of a misleading motor strategy than to a general inability of the motor system to control the movement properly.