Which Scale Best Detects Treatment Response of Tremor in Parkinsonism?

Abstract

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. 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. 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). 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. 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.