Essential pitfalls in "essential" tremor.

Although essential tremor has been considered the most common movement disorder, it has largely remained a diagnosis of exclusion: many tremor and nontremor features must be absent for the clinical diagnosis to stand. The clinical features of "essential tremor" overlap with or may be part of other tremor disorders and, not surprisingly, this prevalent familial disorder has remained without a gene identified, without a consistent natural history, and without an acceptable pathology or pathophysiologic underpinning. The collective evidence suggests that under the rubric of essential tremor there exists multiple unique diseases, some of which represent cerebellar dysfunction, but for which there is no intrinsic "essence" other than a common oscillatory behavior on posture and action. One approach may be to use the term essential tremor only as a transitional node in the deep phenotyping of tremor disorders based on historical, phenomenological, and neurophysiological features to facilitate its etiologic diagnosis or serve for future gene- and biomarker-discovery efforts. This approach deemphasizes essential tremor as a diagnostic entity and facilitates the understanding of the underlying disorders to develop biologically tailored diagnostic and therapeutic strategies.