BACKGROUND: Several scales are available for rating the severity of tremor at 
present. However, the sensitivity to change of these instruments has remained to 
be clarified.
OBJECTIVE: To compare the sensitivity of the Fahn-Tolosa-Marin Tremor Rating 
Scale, the Part III of the Movement Disorder Society-sponsored Unified 
Parkinson's Disease Rating Scale (MDS-UPDRS) and the MDS-UPDRS Tremor Scale to 
the effects of various antitremor treatments.
METHODS: Enrolling subjects with parkinsonism associated with tremor, we 
analyzed two scenarios: (1) tremor changes associated with acute levodopa 
challenge (n = 287) and (2) a 12-month outcome of different treatment options 
(n = 512) including deep brain stimulation (n = 146), levodopa/carbidopa 
intestinal gel infusion (n = 30), and initiating (n = 63) or adjusting oral 
antiparkinsonian medication (n = 273). Changes in tremor scales were assessed by 
effect size values (Cohen's d and eta-square).
RESULTS: Part B of the Fahn-Tolosa-Marin Tremor Rating Scale was the most 
sensitive to acute levodopa challenge (Cohen's d = -1.04, η2 = 0.12). However, 
Part A of the Fahn-Tolosa-Marin Tremor Rating Scale showed the highest effect 
size, which was a small one (Cohen's d = -0.33, η2 = 0.03), for detecting a 
treatment-related change in the severity of tremor during long-term follow-up.
CONCLUSIONS: The Fahn-Tolosa-Marin Tremor Rating Scale has a better ability to 
capture changes due to levodopa challenge or antiparkinsonian treatment than 
MDS-UPDRS Part III or MDS-UPDRS Tremor Scale.