Objective: To assess the importance of polymyographic registration of abnormal movements in differential diagnosis of tremor in orthostatism.

Background: Orthostatic tremor (OT) is typical with extremely synchronous high frequency bursts in lower limbs, described as instability by patients. Despite having this specific presentation, it could be mimicked by other disorders (1).

Method: We examined three patients who were referred with suspicion for orthostatic tremor. They were examined with Neuro-MEP-8CH EMG machine in different positions/situations.

Results: Case 1: 83-years old woman had a four-year history of unsteadiness while standing, less pronounced while walking. Patient presented with hypomimia, mild asymmetrical equivalent parkinsonism, severe postural instability with significant improvement with only subtle support. EMG revealed asynchronous high-frequency burst of 50-80 ms in an action – with elevation of lower limbs, while standing and walking. On the upper limbs, there was asymmetrical 4.5 Hz synchronous tremor consistent with parkinsonian tremor. We concluded orthostatic myoclonus associated with Parkinson’s disease (PD). Case 2: 66-years old woman with DaT-SPECT confirmed PD, had been experiencing tremor of lower limbs while standing, which vanished while walking, and improved after levodopa introduction. We found tremor of lateral vasti muscles and anterior tibial muscles with a frequency of 10 Hz few seconds after standing up, followed by tremor of 5.4 Hz. We confirmed combination of slow orthostatic tremor and typical parkinsonian tremor in PD. Case 3: 24-years old woman had suffered from episodes of high-frequency tremor of both lower limbs while standing or while sitting with feet on the floor, not present while walking. Lower limbs EMG disclose distractible tremor of lower limbs with variable frequency and burst duration in different situations. Together with patient’s history of sudden onset and episodic character clustered during periods of stress exposure, we concluded functional tremor.

Conclusion: Polymyographic registration of abnormal movements is an perfect tool which enables clinicians to distinguish various types of hyperkinetic syndromes connected with up-right position.

References: (1) Apartis E, Tison F, Arne P, Jedynak CP, Vidailhet M. Fast orthostatic tremor in Parkinson’s disease mimicking primary orthostatic tremor. Mov Disord 2001;16:1133-1136.

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