title: The spiral axis as a clinical tool to distinguish essential tremor from dystonia cases.
abstract: BACKGROUND
  Tremor is a common feature of a variety of neurological disorders. In genetic studies of essential tremor (ET), investigators need to screen potential enrollees by mail or telephone to exclude those with other neurological conditions, especially dystonia. In clinical settings, the differentiation of ET and dystonia may also be very challenging. We hypothesized that the spiral axis, described below, is a useful screening tool to distinguish ET cases from dystonia cases.
  
  
  METHODS
  We analyzed the hand-drawn spirals of 135 individuals enrolled in a genetics study at Columbia University Medical Center. Each of the four spirals was assessed for the presence of a single identifiable tremor orientation axis, and a spiral axis score (range = 0-4) [a single axis on all 4 spirals] was assigned to each enrollee.
  
  
  RESULTS
  There were 120 ET cases and 15 cases with dystonic tremor. Most (101/120, 84.2%) ET cases had an axis score ≥1 vs. only half (8/15, 53.3%) of the dystonia cases (p = 0.02). Receiver Operator Curve (ROC) analysis revealed that the use of a spiral axis score ≥2 as a cut off would exclude 60.0% of dystonia cases while including 67.5% of ET cases.
  
  
  CONCLUSIONS
  Handwritten spirals appear to have a single predominant axis in more ET than dystonia cases. The evaluation of this axis has moderate diagnostic validity as a screening tool to distinguish ET cases from those with dystonia. Although this study did not assess the utility of this tool in clinical practice settings, future studies should do so.
authors.affiliation: GH Sergievsky Center, College of Physicians and Surgeons, Columbia University, New York, NY, USA.
authors.forename: Monika
authors.initials: M
authors.lastname: Michalec
authors.affiliation: GH Sergievsky Center, College of Physicians and Surgeons, Columbia University, New York, NY, USA.
authors.forename: Nora
authors.initials: N
authors.lastname: Hernandez
authors.affiliation: Taub Institute for Research on Alzheimer's Disease and The Aging Brain, College of Physicians and Surgeons, Columbia University, New York, NY, USA; Department of Pathology and Cell Biology, Columbia University Medical Center, New York, NY, USA.
authors.forename: Lorraine N
authors.initials: LN
authors.lastname: Clark
authors.affiliation: GH Sergievsky Center, College of Physicians and Surgeons, Columbia University, New York, NY, USA; Taub Institute for Research on Alzheimer's Disease and The Aging Brain, College of Physicians and Surgeons, Columbia University, New York, NY, USA; Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, NY, USA; Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, NY, USA. Electronic address: EDL2@columbia.edu.
authors.forename: Elan D
authors.initials: ED
authors.lastname: Louis
mesh_terms: D000328:Adult; D000368:Aged; D004421:Dystonia / Q000175:diagnosis*; D020329:Essential Tremor / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D012720:Severity of Illness Index; D018709:Statistics, Nonparametric; D016683:Supine Position / Q000502:physiology*
keywords: Axis; Dystonia; Essential tremor; Spiral