For a study, it was determined that for decades it has been contested whether primary writing tremor is a kind of dystonic tremor, a variety of essential tremor, or a distinct entity. Researchers wanted to see if primary writing tremor and dystonia have a similar etiology. Researchers looked at the pathophysiological features of dystonia in patients with primary writing tremors. About 10 patients with idiopathic dystonic tremor syndrome, 7 patients with primary writing tremor, 10 patients with essential tremor, and 10 healthy volunteers were recruited. At baseline, they were subjected to eyeblink classical conditioning, a blink recovery cycle, and transcranial magnetic stimulation testing, which included motor-evoked potentials and short- and long-interval intracortical inhibition. Following the paired-associative plasticity paradigm, transcranial magnetic stimulation measurements were also taken.
The electrophysiological abnormalities in primary writing tremor and dystonic tremor syndrome were similar, consisting of reduced eyeblink classical conditioning learning, reduced blink recovery cycle inhibition, and a lack of effect of paired-associative plasticity on long-interval intracortical inhibition. The latter two results differed from those observed in persons with essential tremors and healthy controls. Although not statistically significant, there was a somewhat lower short-interval intracortical inhibition and a greater effect of paired-associative plasticity in primary writing tremor and dystonic tremor syndrome compared to essential tremor and healthy participants.
Their first notion of shared pathogenesis between dystonia and primary writing tremor was verified. Primary writing tremor may be classified as a kind of dystonic tremor.
Reference:movementdisorders.onlinelibrary.wiley.com/doi/10.1002/mds.28579
