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Primary writing tremor. A form of focal dystonia?
Author(s) -
Elble Rodger J.,
Moody Charles,
Higgins Constance
Publication year - 1990
Publication title -
movement disorders
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.352
H-Index - 198
eISSN - 1531-8257
pISSN - 0885-3185
DOI - 10.1002/mds.870050205
Subject(s) - dystonia , electromyography , coactivation , physical medicine and rehabilitation , focal dystonia , medicine , essential tremor , psychology , neurological disorder , resting tremor , motor unit , central nervous system disease , neuroscience , parkinson's disease , disease
Five patients exhibited severe tremor in the upper extremity, primarily when attempting to write or draw. Electromyography was performed to determine the patterns of muscle activity that were responsible for this tremor. Tremor was measured with an accelerometer and with a digitizing tablet. Two patients had postural tremor that was indistinguishable from mild, high‐frequency essential tremor. All patients exhibited a severe 5–7‐Hz tremor during the acts of writing and drawing. Muscles throughout the affected extremity exhibited rhythmic 5–7‐Hz bursts of motor unit discharge, and the average level of motor unit activity was tonically increased in antagonistic muscles. This abnormal coactivation of antagonistic muscles produced subtle dystonic posturing of the affected limb that was overshadowed by severe tremor. Electromyography was useful in confirming the coexistence of tremor and dystonia in our patients. The nonspecificity of dystonia and postural tremor must be considered when discussing the nosology and pathophysiology of primary writing tremor.