TETRAS does not assess rest tremor but does include an assessment of postural tremor in the “wing-beating” position, in which the elbows are flexed and extended laterally with shoulders abducted, such that the upper limbs are held horizontally with the hands in front of the upper chest. First, the FTM assesses postural tremor in the limbs-extended-forward posture, kinetic tremor in the finger-nose-finger reaching task, and rest tremor while both upper limbs are relaxed on the patient's lap, all of which are performed while the patient is seated. There are 2 main differences in how upper limb tremor is assessed using these scales. 4 The reliability of the water-pouring task was not assessed. Large numbers of raters, rating a small sample of patients, found good intra-rater reliability and fair inter-rater reliability for the tremor location/severity items but only fair intra-rater reliability and poor inter-rater reliability for spiral drawing and handwriting ratings.
3 The reliability of FTM is less established. 2īoth expert and novice raters perform TETRAS with excellent inter-rater and intra-rater reliability. 1 The Essential Tremor Rating Assessment Scale (TETRAS) is a more recently validated scale that was designed specifically for the assessment of tremor severity in patients with ET. The most commonly used scale in large trials has been the Fahn-Tolosa-Marin Clinical Rating Scale for Tremor (FTM).
TETRAS has 2 main advantages over FTM in the assessment of tremor severity: (1) the absence of a ceiling effect in patients with severe ET, and (2) the inclusion of wing-beating tremor.Ĭlinical trials for essential tremor (ET) have employed dozens of different scales and assessments as measures of primary efficacy. Test-retest reliabilities of the other TETRAS and FTM ratings were excellent, and both scales had good sensitivity to treatment effect. In contrast, wing-beating postural tremor, exclusive to TETRAS, exhibited excellent test-retest reliability and a strong correlation with kinetic and limbs-extended-forward postural tremor. Rest tremor, exclusive to FTM, correlated poorly with postural and kinetic tremor and had very poor test-retest reliability. However, FTM exhibited a ceiling effect for severe tremor.
ResultsįTM ratings of postural and kinetic tremor correlated strongly with those of TETRAS.
Upper limb postural and kinetic tremor items from both scales were compared using blinded, video-recorded examinations of patients with moderate-to-severe ET who participated in a trial of focused ultrasound thalamotomy. However, there is no direct comparison of these scales in any clinical trial. TETRAS has anchors that span a larger range of tremor amplitudes (>20 cm = grade 4), making it more suitable for assessing patients with severe ET. The Essential Tremor Rating Assessment Scale (TETRAS) is a validated clinical scale designed specifically for the assessment of ET severity. The Fahn-Tolosa-Marin Clinical Rating Scale for Tremor (FTM) has been used in large trials for essential tremor (ET), but its anchors for ratings from 0 to 4 of upper limb tremor are probably too low for patients with severe tremor (tremor amplitude >4 cm grade 4).