Symposium 2: Movement Disorders SY2.1. Evaluation of Tremor

Abstract

Tremor is defined as an involuntary, rhythmic (regularly recurrent) and oscillatory (rotating around a central plane) movement of the body part. The evaluation of tremor should begin with careful history taking and a focused clinical examination on tremor phenomenology and associated neurological signs. The first step of the approach is to exclude tremor mimics such as myoclonus, clonus or other hyperkinetic movements. The second step is to carefully evaluate clinical features and establish whether the tremor is isolated or combined with other neurological problems and the predominant tremor is at rest or action. Tremor can be classified into syndromes depending on the characteristics (e.g. activation of tremor, distribution of tremor) and prominent additional signs. The common tremor syndromes during action are essential tremor, enhanced physiologic tremor, dystonic tremor, drug-induced tremor, cerebellar tremor, rubral tremor, and orthostatic tremor while the common tremor syndromes at rest are parkinsonian tremor. A detailed tremor history and neurological examination are usually enough for the clinical evaluation of tremor syndromes. However, the clinical presentations are sometimes complex and electrophysiologic investigations can be helpful in making the diagnosis of tremor subtypes. The basic neurophysiologic test is a multi-channel surface EMG combined with accelerometry to assess the distribution of tremor, tremor frequency, and amplitude during various types of activation of tremor, the effect of loading and distraction on tremor frequency and amplitude. The characteristics of central tremor syndromes are more stable tremor frequency and less influenced by loading compared to peripheral tremor syndromes. The peak tremor frequency can be overlapped among tremor subtypes but a unique tremor frequency can be found in some syndrome such as orthostatic tremor, cerebellar tremor and rubral tremor. The specific neurophysiologic procedures including distractibility and entrainment are sensitive and specific for functional tremors. Recently, more advanced neurophysiologic tests have emerged. There is a promising role of intermuscular coherence analysis in the differential diagnosis of tremor subtypes. Evaluation of tremor based on clinical and neurophysiological features are important, leading to the appropriate diagnosis and treatment.