title: Severity stages in essential tremor: a long-term retrospective study using the glass scale.
abstract: BACKGROUND
  Few prospective studies have attempted to estimate the rate of decline of essential tremor (ET) and these were over a relatively short time period (less than 10 years). We performed a long-term study of severity stages in ET using the Glass Scale scoring system.
  
  
  METHODS
  Fifty consecutive patients with severe ET were included. We retrospectively obtained Glass Scale scores throughout the patient's life. Common milestone events were used to help recall changes in tremor severity.
  
  
  RESULTS
  According to the Glass Scale, the age distributions were as follows: score I, 40±17 years, score II, 55±12 years, score III, 64±9 years, and score IV, 69±7 years. A significant negative correlation between age at first symptom and rate of progression was found (r = -0.669, p<0.001). The rate of progression was significantly different (p<0.001) when the first symptom appeared at a younger age (under 40 years of age) compared with older age (40 years or older).
  
  
  CONCLUSIONS
  Our results support the progressive nature of ET. Age at onset was a prognostic factor. The Glass Scale may be a useful tool to determine severity stages during the course of ET in a manner similar to the Hoehn and Yahr Scale for Parkinson's disease.
authors: Movement Disorders Unit, Department of Neurology, Hospital de la Santa CreuiSant Pau, Autonomous University of Barcelona, Barcelona, Catalonia, Spain.
authors: Alexandre
authors: A
authors: Gironell
authors: Movement Disorders Unit, Department of Neurology, Hospital de la Santa CreuiSant Pau, Autonomous University of Barcelona, Barcelona, Catalonia, Spain.
authors: Roser
authors: R
authors: Ribosa-Nogué
authors: Clinical Epidemiology and Public Health Department, Hospital de la Santa CreuiSant Pau, Autonomous University of Barcelona, Barcelona, Catalonia, Spain.
authors: Ignasi
authors: I
authors: Gich
authors: Movement Disorders Unit, Department of Neurology, Hospital de la Santa CreuiSant Pau, Autonomous University of Barcelona, Barcelona, Catalonia, Spain.
authors: Juan
authors: J
authors: Marin-Lahoz
authors: Movement Disorders Unit, Department of Neurology, Hospital de la Santa CreuiSant Pau, Autonomous University of Barcelona, Barcelona, Catalonia, Spain.
authors: Berta
authors: B
authors: Pascual-Sedano
keywords: Essential tremor; Glass Scale; essential tremor progression