Silent Shakes at the Supermarket: Novel Electrophysiological Insights From a Case of Shopping Bag Tremor

Shopping bag tremor (SBT), also known as "weight-holding tremor," represents a rare and diagnostically challenging activation-specific tremor syndrome which is characterized by rhythmical oscillations of the upper limb that appear predominantly during sustained weight-bearing without any overt joint movement (isometric contraction).1 The existing literature diverges on its categorization, with some authors proposing an isometric tremor model based on activation during static contraction, while others align SBT with essential tremor due to its rhythmicity and frequency.[2][3][4] Also, unlike the classical taskspecific tremor, which is typically associated with learned motor skills (eg, playing an instrument, writing), SBT is not associated with a skilled activity/fine motor task but, rather, is defined by the mechanical demand imposed by weight-holding.4 Despite isolated case reports, comprehensive phenotyping of this unique tremor and systematic electrophysiological profile of SBT is lacking.This paper aims to fill that gap by presenting detailed clinical and Electromyography (EMG) findings, exploring posture-and load-dependent tremor amplitude variation, and critically reviewing the current nosological frameworks.