[Postural tremor and dystonia. Clinical aspects and physiopathological considerations]

The coexistence of tremor and dystonia is usually seen but there is not a satisfactory explanation for it. Some consider that essential tremor (ET) and idiopathic dystonia (ID) may be genetically linked. To clarify this relationship we evaluated the frequency of postural hand tremor in ID and symptomatic dystonia (SD) patients. We studied the records of patients with dystonia seen in our Movement Disorders Unit. ID was considered when there was no other neurological abnormality in the examination aside from dystonia, normal laboratorial tests and neuroimaging related to dystonia, and a negative past history for any known cause for it, except for genetic predisposition. We analyzed the clinical characteristics of dystonia and the occurrence of postural tremor. We collected 185 patients, being 120 with ID and 65 with SD. Tremor was seen in 27 (22.5%) of ID and 14 (21.5%) of SD. Tremor was present in either focal, segmental or generalized dystonia in both ID and SD. Family history for ET was absent in all patients. The similar frequency of tremor in ID and SD patients suggests that the pathophysiologic derangement resulting in dystonia can favor the development of tremor.