Highlighting the value of polymyography in childhood onset movement disorders.

Introduction: Characterizing hyperkinetic Movement Disorders (MD) in children is challenging, particularly when distinguishing tremor from myoclonus. Polymyography (EMG combined with accelerometry) and EEG jerk-locked back-averaging are well-established diagnostic tools in adults but are rarely applied in paediatric population. This study aimed to assess the feasibility and contribution of individualized neurophysiological investigations to the classification of hyperkinetic MD in children. Materials and methods: We retrospectively reviewed clinical and neurophysiological data from consecutive patients who underwent polymyography over a two-year period being referred for unclear clinical MD phenomenology. A pediatric MD specialist and a neurophysiologist jointly performed evaluations. Results: 56/60 patients were included (four were excluded due to absent MD during recording or lack of cooperation). Myoclonus was the most frequent polymyography diagnosis (55%), followed by tremor (36%). Initial clinical diagnoses were confirmed in 62% of cases: all suspected cases of myoclonus were validated, whereas 48% patients initially diagnosed with tremor were reclassified as having myoclonus. Polymyography revealed additional MD in 18% of patients, most often myoclonus, and supported a neurofunctional aetiology in one case. After the polymyography, symptomatic pharmacological treatment-mainly for tremor and cortical myoclonus-was proposed in 34%. Additional genetic investigations were suggested in 30% of patients. Discussion and conclusion: Polymyography proved feasible even in young children, including those with intellectual disability. Combined with expertise of an MD specialist, polymyography significantly improves diagnostic accuracy, particularly tremor vs. myoclonus, and guides both aetiologic and therapeutic management. These findings highlight the value of integrating polymyography into paediatric MD evaluation.