Dystonic tremor.

Dystonic tremor is a new and still poorly defined clinical entity. It seems to be generally accepted that tremor in the setting of obvious dystonia should be classified in this category. It may occur in generalized, segmental, and focal dystonias as well as in primary and secondary dystonias. In primary dystonia dystonic tremor may precede the occurrence of clear signs of dystonia which hence causes uncertainty about the classification of this condition. Secondary criteria like persistently focal tremor in one extremity, jerky and irregular tremors, gestes antagonistes, or selective responsiveness to antidystonic therapeutic agents may be helpful to distinguish this entity. The occurrence of dystonic tremor in symptomatic cases is often seen following thalamic lesions, peripheral injuries or in dystonia associated with sympathetic reflex dystrophy. The pathophysiology is unknown. Reciprocal inhibition and other inhibitory reflex pathways at various levels seem to be reduced at least in some cases with dystonic tremors.