Electrophysiological testing aids the diagnosis of tremor and myoclonus in clinically challenging patients
Cheryl S. J. Everlo, Jan Willem J. Elting, Marina A.J. Tijssen, A.M. Madelein van der Stouwe
Abstract
Objective: We investigated how clinical neurophysiological testing can help distinguish tremor and myoclonus and their subtypes. Methods: We retrospectively analysed clinical and neurophysiological data from patients who had undergone polymyography (EMG + accelerometry) to diagnose suspected tremor or myoclonus. We show a systematic approach, which includes contraction pattern, rhythm regularity, burst duration and evidence of cortical drive. Results: We detected 773 patients in our database, of which 556 patients were ultimately diagnosed with tremor (enhanced physiological tremor n = 169, functional tremor n = 140, essential tremor n = 90, parkinsonism associated tremor n = 64, cerebellar tremor n = 19, Holmes tremor n = 12, dystonic tremor n = 8, tremor not further specified n = 9), 140 with myoclonus and 23 with a combination of tremor and myoclonus. Polymyography confirmed the presumptive diagnosis in the majority of the patients and led to a change of diagnosis in 287 patients (37%). Conversions between diagnoses of tremor and myoclonus occurred most frequently between enhanced physiological tremor, essential tremor, functional tremor and cortical myoclonus. Conclusions: Neurophysiology is a valuable additional tool in clinical practice to differentiate between tremor and myoclonus, and can guide towards a specific subtype. Significance: We show how the stepwise neurophysiological approach used at our medical center aids the diagnosis of tremor versus myoclonus.