How Do I Examine for Re-Emergent Tremor?

Although rest tremor is the typical form of tremor associated with Parkinson's disease (PD), particularly the tremor-dominant subtype,1 parkinsonian patients may also exhibit postural tremor. In many parkinsonian patients, this postural tremor emerges after a latency of a few seconds or even minutes. In our original description, we coined the term "re-emergent tremor" to differentiate this postural tremor from essential tremor, which occurs without any latency, and to link it to PD rest tremor that is "reset" after some latency when a new holding posture is assumed.2 The relationship of this re-emergent tremor to the typical rest tremor is supported by the observation that this tremor shares many characteristics with the typical rest tremor, such as the same, 3 to 5-Hz frequency, occasional supinating-pronating component, and relatively good response to dopaminergic therapy. Rarely, postural tremor, occurring after a brief (2-4 seconds) latency can be seen even without observable rest tremor.3 In most patients with PD, it is the postural (re-emergent) tremor that is more troublesome for them than the typical rest tremor, because this re-emergent tremor interferes with their ability to hold objects, such as newspapers, against gravity and results in spilling of liquids. Postural tremor of PD is often misdiagnosed as essential tremor, and this diagnostic challenge can be further confounded when both conditions coexist.4 When that occurs, the postural tremor is present without latency, although the amplitude may gradually increase as the underlying re-emergent tremor becomes more evident.