Repeated Spiral Drawings in Essential Tremor: a Possible Limb-Based Measure of Motor Learning

Abstract

To investigate changes in tremor severity over repeated spiral drawings to assess whether learning deficits can be evaluated directly in a limb in essential tremor (ET). A motor learning deficit in ET, possibly mediated by cerebellar pathways, has been established in eye-blink conditioning studies, but not paradigms measuring from an affected, tremulous limb. Computerized spiral analysis captures multiple characteristics of Archimedean spirals and quantifies performance through calculated indices. Sequential spiral drawing has recently been suggested to demonstrate improvement across trials among ET subjects. One hundred and sixty-one ET and 80 age-matched control subjects drew 10 consecutive spirals on a digitizing tablet. Degree of severity (DoS), a weighted, computational score of spiral execution that takes into account spiral shape and line smoothness, previously validated against a clinical rating scale, was calculated in both groups. Tremor amplitude (Ampl), an independent index of tremor size, measured in centimeters, was also calculated. Changes in DoS and Ampl across trials were assessed using linear regression with slope evaluations. Both groups demonstrated improvement in DoS across trials, but with less improvement in the ET group compared to controls. Ampl demonstrated a tendency to worsen across trials in ET subjects. ET subjects demonstrated less improvement than controls when drawing sequential spirals, suggesting a possible motor learning deficit in ET, here captured in an affected limb. DoS improved independently of Ampl, showing that DoS and Ampl are separable motor physiologic components in ET that may be independently mediated.

Holmes Tremor due to Artery of Percheron Infarct: Clinical Case and Treatment Using Deep Brain Stimulation of the Vim and ZI Targets

“…This tremor profile is consistent with the previous finding that the DoS and tremor amplitude are separable motor physiologic components in tremor that may be independently mediated. 18 The tremors in this subject were complex, with multiple axes, varying frequencies, drawing irregularity, and several other abnormal motor physiological features. Postoperatively in this subject, we found overall improvement in most, but not all, objective measures.…”

“…This is a technique for measuring kinematic and other attributes of spiral drawing 12 that uses a digitizing tablet and computer and calculates a series of mathematical indices to assess upper limb motor function. Spiral analysis has been used to evaluate neurological disorders, [13][14][15][16][17] to show motor learning in Essential Tremor (ET) 18 and to help predict the responses to DBS in ET subjects. 19 For this study, we used spiral analysis outcome measures with specific clinical relevance to tremor, parkinsonism, and cerebellar dysfunction.…”

Does Cup-Grip Type Affect Tremor among People with Essential Tremor?

“…Deviations of the acceleration from the filtered signal and the sum of square errors/ deviations (SSE) were computed. The SSE was then normalized by the number of sampling points (nSSE): nSSE between acceleration and filtered signal using LPF for the X , Y and Z axes; total deviations, computed as the sum of nSSE from the X , Y and Z axes (TnSSE = nSSE x + nSSE y + nSSE z ); nSSE between acceleration and filtered signal using a moving average window (width of 20 points) in the X and Y axes; and mean amplitude computed from averaged consequential peaks for the X , Y and Z axes [ 16 , 34 ]. Because not all frequency-domain analyses resulted in single, clear, main peak amplitude, the last outcome measure was computed to compare the amplitude calculated from FFT.…”

Why is Essential Tremor so Difficult to Treat? A Literature Review

“…Clinical assessments include characterizing the tremor frequency range as low (below 4Hz), medium (between 4 to 8 Hz), or high (greater than 8 Hz) to confirm the presence of pathological tremor [14]. Pathological tremors are often detected when the frequency of tremor ranges between 4-12 Hz [14], [18]. A popular test for ET patients consists of spiral drawing inspections that are used as a qualitative task for the diagnosis of ET.…”

“…A popular test for ET patients consists of spiral drawing inspections that are used as a qualitative task for the diagnosis of ET. During this task, a patient's drawing of Archimedes spirals is captured to identify abnormal movements [9], [18]. Another assessment used is the Essential Tremor Rating Assessment Scale (TETRAS), which is an accurate and comprehensive tool used to assess the severity of ET [19].…”