Reliability of a new scale for essential tremor

Background: The objective of this study was to determine the reliability of a new scale for the clinical assessment of essential tremor. The Essential Tremor Rating Assessment Scale contains 9 performance items that rate action tremor in the head, face, voice, limbs, and trunk from 0 to 4 in half-point intervals. Head and limb tremor ratings are defined by specific amplitude ranges in centimeters. Methods: Videos of 44 patients and 6 controls were rated by 10 specialists on 2 occasions 12 months apart. Inter- and intrarater reliability was assessed with a 2-way random-effects intraclass correlation, using an absolute agreement definition. Results: Inter- and intrarater intraclass correlations for head and upper-limb tremor ranged from 0.86 to 0.96, and intraclass correlations for total score were 0.94 and 0.96. The intraclass correlations for voice, face, trunk, and leg were less robust. Conclusions: This scale is an exceptionally reliable tool for the clinical assessment of essential tremor. (c) 2012 Movement Disorder Society