Clinical Differentiation of Essential Tremor and Parkinson's Disease

Abstract

We present clinical features and tremor characterization in a patient with Parkinson's disease (PD) as well as in two cases of essential tremor (ET) with some parkinsonian features but no evidence of dopaminergic terminal loss on 123 I-FP-CIT Single Photon Emission Computed Tomography (SPECT). Relatively slow frequency rest tremor and bilateral upper extremity bradykinesia without decrementing amplitude were observed in the ET cases, with unilaterally decreased arm swing in case 3. Alternating rest tremor and re-emergent tremor with 13 second latency was confirmed in the PD case. Re-emergent tremor had alternating characteristics, which to our knowledge has not been previously reported. The ET cases had synchronous postural tremor. Alternating re-emergent tremor in PD provides further evidence for re-emergent tremor as an analogue of rest tremor in PD. Two cases of ET with synchronous postural tremor and one to two year history of parkinsonian features had no evidence of dopaminergic terminal loss up to 40 years after the initial onset of ET. Tremor synchronicity characterization can assist in differential diagnosis between the two disorders.

Re‐emergent tremor in Parkinson's disease: the effect of dopaminergic treatment

“…RET differs from the postural tremor that is present in PD while a posture is maintained . As both the frequency and muscle contraction pattern are similar in RET and resting tremor, it has been suggested that RET is a variant of resting tremor .…”

Re-emergent tremor in Parkinson's disease

“…The authors defined this tremor as "re-emergent tremor" (RET) and suggested that RET might be a possible clinical variant of RT [6]. This hypothesis was based on the observation that the two tremors share similar frequency characteristics [6,7] and a similar asynchronous muscle activation pattern [8].…”

Re-Emergent Tremor: What do we know so Far?

“…Furthermore, Belvisi et al, [5] observed that the severity of non-motor symptoms was also similar in the two groups of patients. Previous accelerometric [1,11] and electromyographic recordings [12] have shown that both the frequency (about 4.5-5.5 Hz) and the asynchronous pattern of antagonistic muscle activation [6,12] are similar in RET and resting tremor. The severity of RET positively correlates with that of resting tremor in PD patients on treatment [5].…”

“…In PD, RET usually involves the upper limbs [1,[4][5][6] and is bilateral in 50% of cases [5]. Recent clinical reports have described patients with PD with RET even in the jaw [7] and tongue [8,9].…”