Clinical markers of cerebellar tremor of the upper limb

Introduction/Background Hypermetric tremor, from cerebellar origin, directly relate to iterative hypermetria by delayed antagonist correction at each movement, is a frequent neurological disorder, which can cause significant functional and social disability. Nowadays, the clinical evaluation of tremors relies mainly on subjective rating tools. The purpose of the study was to develop quantitative markers of hypermetric tremor of the upper limb to help clinicians with diagnosis, follow-up and assessment of treatment effects. Material and method We prospectively analyzed data from two volumetric tests (30 seconds and 5 table-to-mouth tests), a device for evaluating rapid alternating pronosupination movements “the Hand Tapper” (large/small movements ratios) and spiralography (number of spikes per turn and symmetry coefficient). We compared these parameters in three populations: 18 patients (age: 63 ± 16 years) with upper limb cerebellar tremor, 15 patients with Parkinson's disease with predominant tremor (67 ± 7 years) and 18 healthy subjects (age: 63 ± 15 years). Results At the volumetric tests, the height of remaining water is measured in the polystyrene cup (90 mm height) after each test. For the 30 seconds posture test (H30): cerebellar = 41.2 ± 8.5 mm, parkinson = 82.9 ± 4.5 mm, healthy subjects = 90.0 ± 0.0 mm, (P cerebellar vs parkinson = 2 × 10−5) and for the 5 table-to-mouth back and forth movements test (HX5): cerebellar = 27.3 ± 7.6 mm, parkinson = 88.7 ± 0.3 mm, healthy subjects = 89.9 ± 0.1 mm (P cerebellar vs parkinson = 10−11). At the “Hand Tapper”, the large/small pronosupination movements ratios (L/S) were: cerebellar = 65.0 ± 4.6%, parkinson = 50.2 ± 2.2%, healthy subjects = 47.9 ± 3.0% (P cerebellar vs parkinson = 0.01). At the spiralography, the number of spikes per turn were: cerebellar = 10.7 ± 1.7; parkinson 6.1 ± 1.3; healthy subjects = 2.0 ± 0.3 (P cerebellar vs parkinson = 0.03). Conclusion The height of remaining water on volumetric tests, L/S ratios with Hand Tapper, and the number of spicules on spiralography seem to be representative markers of cerebellar hypermetry, compared to “parkinsonism”. Explorations of diagnostic performances of these parameters and correlations with the severity of the tremor will be the subject of a future analysis.