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Session: Neuromuscular – upper extremities
Session starts: Friday 25 January, 10:30
Presentation starts: 10:45
Room: Lecture room 535

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Zeus Tlaltecutli Dominguez Vega (UMCG)
Gerrit Kramer (UMCG)
Jan Willem Elting (UMCG)
Marina A J Tijssen (UMCG)
Natasha M Maurits (UMCG)

Abstract:
Background: Visual assessment of a patient’s tremor during a visit to the outpatient clinic can be considered only a snapshot. Sometimes electromyography or accelerometry can be used for longer offline assessment of tremor characteristics such as intensity, frequency and occurrence, which are the most common tremor characteristics used for tremor quantification. Despite that some investigations have studied these characteristics with long-term tremor recordings, inconsistencies in recording times have not been addressed. Objective: To determine the minimum number of days needed to obtain reliable estimates of quantified tremor presence and frequency variability from long-term tremor recordings using accelerometry. Methods: Inertial sensor data were recorded from 34 tremor patients (16 functional tremor (FT), 18 organic tremor (OT)) during unconstrained activities of daily living during 30 days, each day over a 10-hour period. Sensors were attached to the dorsal side of the forearm. Start and end of recording per day were obtained from electronic patient diaries. The accelerometer signal and a tremor identification algorithm [1] implementing the periodogram were used to identify time windows with tremor, from which the percentage of tremor and tremor frequency variability were calculated per patient across all days. Non-parametric distributions were generated and Z-tests performed to determine whether estimates of tremor characteristics obtained from one up to fifteen days were representative of estimates obtained from any one up to fifteen days within the entire thirty days. Results: Tremor percentage as estimated from the full 30 days ranged from 11.17 to 31.17% for FT patients and from 10.17 to 70.0% for OT patients. Frequency variability ranged from 0.73 to 2.0 Hz for FT patients and from 0.4 to 1.5 Hz for OT patients. The shortest period of time needed to obtain reliable estimates of these tremor characteristics was found to be seven days for FT patients and one day for OT patients. Conclusions: While one day suffices for OT patients, seven days are needed to obtain reliable estimates of tremor presence in FT patients. This is likely due to higher tremor variability in FT patients. Our findings have potential impact for future diagnostic and monitoring purposes in tremor disorders.