title: The "head snap": a subtle clinical feature during the finger-nose-finger maneuver in essential tremor.
abstract: BACKGROUND
  Essential tremor is characterized by several hyperkinetic movements, including arm and head tremors. We report another movement of the head in patients with essential tremor, which we term the "head snap." This was observed as a jerking motion of the head in some patients while they performed the finger-nose-finger maneuver.
  
  
  METHODS
  We compared the prevalence of the head snap in essential tremor patients vs. Parkinson's disease patients. We also assessed the clinical correlates of the head snap.
  
  
  RESULTS
  Ten (20%) of 50 essential tremor patients exhibited a head snap of any severity (rating ≥0.5) vs. 0 of 50 Parkinson's disease patients (p = 0.001). Patients with head snap had more severe arm tremor on Archimedes spiral drawings (p = 0.019) and were more likely to have head tremor (p = 0.03) than those without it.
  
  
  CONCLUSIONS
  This sign could be a useful aid in the clinical diagnosis of tremor.
authors.affiliation: GH Sergievsky Center, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America ; Tufts University School of Medicine, Boston, Massachusetts, United States of America.
authors.forename: Eliezer J
authors.initials: EJ
authors.lastname: Sternberg
authors.forename: Roy N
authors.initials: RN
authors.lastname: Alcalay
authors.forename: Oren A
authors.initials: OA
authors.lastname: Levy
authors.forename: Elan D
authors.initials: ED
authors.lastname: Louis
keywords: Essential tremor; Parkinson's disease; clinical; diagnosis; examination