Objective: This study aimed to investigate whether re-emergent tremor (RET) might also occur in essential tremor (ET) and if the cases with this additional sign should be labelled as ET plus.

Background: In the Consensus Statement on the Classification of Tremors proposed in 2018 by the Task Force on Tremor of the International Parkinson and Movement Disorder Society, ET plus was defined as follows: “Tremor with the characteristics of ET and additional neurological signs of uncertain significance such as impaired tandem gait, questionable dystonic posturing, memory impairment, or other mild neurologic signs of unknown significance that do not suffice to make an additional syndrome classification or diagnosis”. However, this document does not specify if re-emergent tremor could be considered as a mild neurologic sign of unknown significance that leads to the diagnosis of ET plus since re-emergent tremor is described as a highly specific parkinsonian feature useful to distinguish between rest tremor of ET plus and rest tremor in the context of parkinsonian syndromes.

Method: A series of 87 patients diagnosed with ET or ET plus of our Movement Disorders Unit was revised in order to identify patients with RET. DatSCAN imaging was requested in all cases with RET in order to increase the diagnostic certainty of ET/ET plus and only the cases with normal results were further investigated. Demographic variables, presence of other ET plus features, and clinical response of the tremor to specific medications were recorded and statistically analysed.

Results: About 10% of ET and ET plus patients of our series exhibit RET with neither clinical nor nuclear imaging evidence of nigrostriatal degeneration.

Conclusion: Re-emergent tremor might be considered as a soft neurologic sign within the spectrum of ET plus. Nevertheless, because of its rarity, a thorough revision of the patient’s current and past medications and performing DatSCAN imaging seem to be appropriate prior to diagnosis in order to discard pharmacological causes or paucisymptomatic PD.

References: Bhatia, K. P., Bain, P., Bajaj, N., Elble, R. J., Hallett, M., Louis, E. D., Raethjen, J., Stamelou, M., Testa, C. M., Deuschl, G., & Tremor Task Force of the International Parkinson and Movement Disorder Society (2018). Consensus Statement on the classification of tremors. from the task force on tremor of the International Parkinson and Movement Disorder Society. Movement disorders : official journal of the Movement Disorder Society, 33(1), 75–87. https://doi.org/10.1002/mds.27121

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MDS Abstracts - https://www.mdsabstracts.org/abstract/re-emergent-tremor-in-essential-tremor-a-plus-sign-for-et-plus/