The Ice Test to Differentiate Essential tremor from Parkinson’s disease tremor

Congratulations to Drs. Aparna Wagle Shukla, Michael Okun, and  David Vaillancourt on the publication of “The Ice Test to Differentiate Essential tremor from Parkinson’s disease tremor,” which was published in the September 8th issue of Clinical Neurophysiology.


Essential tremor (ET) is characterized by bilateral postural and action tremor of the arms with occasional mild resting tremor.(Louis, 2016) Parkinson’s disease (PD) in contrast has resting tremor as a core clinical feature, whereas postural and action tremor can be seen in 40-70% of patients. Clinical differentiation of ET and PD is often challenging especially given that a significant proportion of PD patients may have a mixed resting and postural tremor.(Lance et al., 1963) DAT SPECT imaging, although FDA approved for differentiation of ET and PD tremors, is expensive and may not always be readily available. Nearly two decades ago, Cooper et al reported that limb cooling significantly suppresses arm tremor in ET and did not have effects in PD.(Cooper et al., 2000) Since this report, the ability of limb cooling effects to differentiate ET from PD has never been replicated. Besides in this study, the tremor for the participating subjects was not clinically characterized. It was not clear whether PD participants had postural/action tremor, reemergent tremor or isolated rest tremor. Postural and action tremor in PD is considered to have a distinct pathophysiology and is more likely to be confused with ET. We therefore sought to examine and confirm the effects of limb cooling on postural and action tremor in ET and PD using a bedside ice test.

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