Is there evidence of bradykinesia in essential tremor?

Abstract

Background and purpose Essential tremor (ET) is a movement disorder primarily characterized by upper limb postural and kinetic tremor. Although still under‐investigated, bradykinesia may be part of the phenotypic spectrum of ET. The aim was to evaluate bradykinesia features in ET through clinical examination and kinematic analysis of repetitive finger movements. Data collected in ET patients were compared with those recorded in Parkinson’s disease patients and healthy controls. Methods Overall, 258 subjects participated in the study (90 ET patients, 84 Parkinson’s disease patients and 84 healthy controls). Repetitive finger tapping was kinematically recorded using a motion analysis system. Movement velocity, amplitude and decrement (sequence effect) were measured. The three groups were first compared by one‐way analysis of variance. A cluster analysis was also performed to better address the data variability observed in ET patients. Possible relationships between kinematic and clinical data were assessed in ET patients. Results Essential tremor patients were slower than healthy controls. Movement slowness in ET did not correlate with postural or kinetic tremor severity. It was also found that movement slowness in ET was not associated with a sequence effect, which instead is a common feature in Parkinson’s disease. Cluster analysis showed that a proportion of ET patients may have movement abnormalities similar to those observed in Parkinson’s disease. Conclusions Movement slowness without sequence effect is a common feature in ET patients. The present findings are relevant when interpreted in the context of the new tremor classification system and in the development of a more accurate bradykinesia definition.

Clinical and Kinematic Features of Valproate-Induced Tremor and Differences with Essential Tremor

“…Kinematic recordings were performed using an optoelectronic system (SMART motion system, BTS Engineering, Italy) consisting of three infrared cameras (sampling rate of 120 Hz) and reflective markers of negligible weight taped to the subject's arms, trunk and head [15][16][17]. For the upper limbs, we used four markers placed on the distal phalange of the index finger and on the second metacarpal bone of each hand.…”

“…To derive the head coordinate system, we used three reflective markers: two placed over the frontal orbital processes (bilaterally) and one placed over the nasion. Three markers were also placed on the trunk to define a reference plane that allowed possible contamination due to trunk movements to be excluded from the upper arm and head movement recordings [15][16][17]. Upper limb postural tremor was recorded: (i) with the arms outstretched in front of the chest (posture 1), and (ii) with the arms flexed at the elbows i.e.…”

“…Three 45-s recordings were obtained for each posture. Upper limb kinetic tremor was recorded in three 15s recording blocks during a 'pointing task', in which subjects were asked to repetitively move their index finger from their nose to a reflective target fixed on a heavy support approximately 15 cm above the table at sternal height and at approximately 2/3 arm distance [15][16][17]. Rest tremor of the upper limbs and head was recorded while patients sat comfortably on a chair facing the cameras, with their arms lying on a desk in front of them.…”

“…Rest tremor of the upper limbs and head was recorded while patients sat comfortably on a chair facing the cameras, with their arms lying on a desk in front of them. Three 45-s recordings per patient were collected [15][16][17].…”

“…In the present study, we aimed to better characterise clinical and kinematic features of VIT using standardized clinical scales and an objective assessment of tremor through motion analysis [15][16][17]. To this aim, we investigated postural, kinetic and rest tremor in different body parts, including the upper limbs and head [15][16][17]. We investigated possible correlations between demographic, clinical and kinematic data in VIT patients.…”