Characterizing Orthostatic Tremor Using a Smartphone Application.

BACKGROUND: Orthostatic tremor is one of the few tremor conditions requiring an electromyogram for definitive diagnosis since leg tremor might not be visible to the naked eye.

PHENOMENOLOGY SHOWN: An iOS application (iSeismometer, ObjectGraph LLC, New York) using an Apple iPhone 5 (Cupertino, CA, USA) inserted into the patient's sock detected a tremor with a frequency of 16.4 Hz on both legs.

EDUCATIONAL VALUE: The rapid and straightforward accelerometer-based recordings accomplished in this patient demonstrate the ease with which quantitative analysis of orthostatic tremor can be conducted and, importantly, demonstrates the potential application of this approach in the assessment of any lower limb tremor.