title: Clinical correlates of action tremor in Parkinson disease.
abstract: BACKGROUND
  Action tremor is often noted in patients with Parkinson disease (PD), yet the clinical correlates of this type of tremor have been the focus of few studies. It is not clear whether this action tremor is a manifestation of the underlying basal ganglia disease.
  
  
  OBJECTIVE
  To determine whether the severity of action tremor in PD is associated with age, age at disease onset, disease duration, levodopa dose, severity of rest tremor, or other motor (ie, bradykinesia, rigidity) and nonmotor manifestations of PD.
  
  
  METHODS
  Patients with PD (N = 197) were ascertained as part of a familial aggregation study. All patients underwent a neurological examination. Rest tremor was rated with the Unified Parkinson Disease Rating Scale; and action tremor, with the Washington Heights-Inwood Genetic Study of Essential Tremor Rating Scale.
  
  
  RESULTS
  Action tremor was present in 184 (93.4%) of 197 patients. Four patients (2%) met criteria for definite essential tremor. The action tremor score was not associated with age, age at onset, or disease duration. The action tremor score was associated with the rest tremor score (r = 0.37; P<.001), and more strongly with the ipsilateral than contralateral rest tremor score. The association between the action tremor score and the rest tremor score was diminished but still significant (r = 0.21, P<.02) even when we excluded these 63 patients with re-emergent tremor. Neither the action nor the rest tremor score was associated with the bradykinesia or rigidity scores, Hoehn and Yahr scale score, or modified Mini-Mental State Examination score.
  
  
  CONCLUSIONS
  Action tremor was associated with rest tremor in PD, suggesting that, at least in part, action tremor is a manifestation of the underlying basal ganglia disease. Neither tremor was associated with other motor and nonmotor manifestations of PD. This in turn suggests that tremor in PD may represent an underlying pathophysiological process different from these other manifestations.
authors.affiliation: Gertrude H Sergievsky Center, College of Physicians and Surgeons, Columbia University, New York, NY, USA. EDL2@columbia.edu
authors.forename: E D
authors.initials: ED
authors.lastname: Louis
authors.forename: G
authors.initials: G
authors.lastname: Levy
authors.forename: L J
authors.initials: LJ
authors.lastname: Côte
authors.forename: H
authors.initials: H
authors.lastname: Mejia
authors.forename: S
authors.initials: S
authors.lastname: Fahn
authors.forename: K
authors.initials: K
authors.lastname: Marder
mesh_terms: D000328:Adult; D017668:Age of Onset; D000368:Aged; D000369:Aged, 80 and over; D000978:Antiparkinson Agents / Q000627:therapeutic use; D001132:Arm; D005260:Female; D006801:Humans; D018476:Hypokinesia / Q000503:physiopathology; D007980:Levodopa / Q000627:therapeutic use; D008297:Male; D008609:Mental Status Schedule; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology; D009068:Movement / Q000502:physiology; D009127:Muscle Rigidity / Q000503:physiopathology; D010300:Parkinson Disease / Q000235:genetics* / Q000503:physiopathology* / Q000523:psychology; D010808:Physical Examination; D011187:Posture; D012146:Rest; D014202:Tremor / Q000209:etiology* / Q000503:physiopathology; D014741:Video Recording
chemical_list: D000978:Antiparkinson Agents; D007980:Levodopa