Introduction: Computerized spiral analysis is a clinical test that captures kinematic, dynamic, and spatial attributes of Archimedean spirals, and calculates a series of indices to quantify disability and assess motor performance. The popularity of tablet computers, such as the Apple iPad (Apple Inc., Cupertino, CA) provides an opportunity to expand the availability of computerized spiral analysis. Finger drawing, however, is limited in its precision and clinical relevance. New technologies such as the Apple Pencil allow for more precise measurements of traditional x, y position data in addition to collection of new dimensions of movement data such as stylus pressure and tilt angle that overcome many of finger drawing's limitations.
Methods: We have created an iPad App that displays a 10x10 cm box in which patients are instructed to freely draw an Archimedean spiral using the Apple Pencil. Twenty spirals are collected in total, 10 from each hand. Data are collected at a 240Hz sampling frequency, higher than the clinically validated Wacom tablet currently in use (Intuos 4, Wacom Technology Corp, Vancouver, WA). The position data, timing, and pressure of each point are recorded and formatted properly in a text file, which is then sent via encrypted email for off-line analysis to ensure data privacy and integrity.
Results: Our analysis software, originally designed to take input from a Wacom tablet, calculates dozens of motor indices of upper limb motor control from spiral data, such as drawing speed, smooth, tremor amplitude, direction, and frequency, loop spacing and variability and pressure information. An overall degree of severity index based on a 5-point scale is also calculated as a nonlinear combination of several indices, approximating expert clinicians analysis of the spiral.
Conclusions: The Apple Pencil and iPad Pro are new technologies that enable precise graphonomic data capture on a large scale that was previously not possible.
Patient Care: With iPad spiral acquisition, automated graphonomic data collection can aid in the monitoring of patients with movement disorders and will provide clinicians with more data from which better decisions can be made regarding patient care, such as drug dosage or DBS electrode pulse frequency modification. This even has the potential to be used as an intraoperative measure of movement dysfunction in patients as they undergo DBS for motor diseases.
Learning Objectives: Assess the ability to precisely capture motor dysfunction on the iPad through computerized spiral analysis.
References: Stanley, K., et al. (2010). "Digitized spiral analysis is a promising early motor marker for Parkinson Disease." Parkinsonism Relat Disord 16(3): 233-234.
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Pullman, S. L. (1998). "Spiral analysis: a new technique for measuring tremor with a digitizing tablet." Mov Disord 13 Suppl 3: 85-89.