title: Rest tremor suppression may separate essential from parkinsonian rest tremor.
abstract: Rest tremor at 4-6 Hz is typical for classical rest tremor (PT) of Parkinson's disease (PD). But rest tremor also appears in other tremor syndromes and may therefore cause a misdiagnosis. In this study we evaluated if suppression of tremor during movement onset is a characteristic feature of Parkinsonian Tremor distinguishing PT from Essential tremor (ET) and if this sign can be reliably diagnosed. Clinically diagnosed patients with PT (n = 44) and ET (n = 22) with rest tremor were included. Video sequences were recorded according to a standardized protocol focusing on the change of tremor amplitude during transition from rest to posture (test 1) or to a target-directed movement (test 2). These videos were assessed for rest tremor suppression by 4 reviewers (2 specialists and 2 residents) blinded to the clinical diagnosis and were compared to the personal assessment of an unblinded movement disorder specialist. Rest tremor suppression was found in 39/44 PD patients and in 2/22 patients with ET during the personal assessment. Rest tremor suppression showed a high sensitivity (0.92-1.00) and an acceptable specificity (0.69-0.95) for PD tremor in both tests. The interrater-reliability of the video-sequences was good to very good (κ 0.73-0.91). Less than 3% of the video sequences were misclassified. We conclude that the assessment of the suppression of rest tremor during movement initiation is a simple and reliable tool to separate PT from rest tremor in ET also suggesting that the mechanisms of rest tremor in these two diseases are different.
authors.affiliation: Department of Neurology, Christian-Albrechts-University, Kiel, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Papengut
authors.forename: Jan
authors.initials: J
authors.lastname: Raethjen
authors.forename: Andreas
authors.initials: A
authors.lastname: Binder
authors.forename: Günther
authors.initials: G
authors.lastname: Deuschl
mesh_terms: D000368:Aged; D016009:Chi-Square Distribution; D004311:Double-Blind Method; D004576:Electromyography; D020329:Essential Tremor / Q000150:complications / Q000175:diagnosis*; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000150:complications*; D012189:Retrospective Studies; D012720:Severity of Illness Index; D014202:Tremor / Q000175:diagnosis* / Q000209:etiology*; D014741:Video Recording