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. 2021 Nov 22;21(1):457.
doi: 10.1186/s12883-021-02486-0.

Diagnosis of orthostatic tremor using smartphone accelerometry

Nicholas E Calvo  1 , Joseph M Ferrara  2   3
Affiliations

Diagnosis of orthostatic tremor using smartphone accelerometry

Nicholas E Calvo et al. BMC Neurol. .

Abstract

Background: Primary orthostatic tremor (OT) is a rare movement disorder characterized by a 13-18 Hz leg tremor, which arises when standing and is relieved by walking/sitting. Those affected generally do not fall, but experience fear of falling, lessened by ambulation. Because of its low amplitude, the tremor is not readily visible, and diagnosis requires confirmation with surface electromyography (sEMG). Recently, applications using the accelerometer feature of smartphones have been used to detect and quantify tremors, including OT, though the accuracy of smartphone accelerometry (SPA) in diagnosing OT is unknown.

Methods: We completed SPA in consecutive adults (18+ years), who presented to our neurology clinic with either subjective leg shakiness upon standing or unsteadiness when standing that lessened with ambulation, which comprised 59 of 2578 patients. We assessed tremor using the StudyMyTremor application on an iPhone 6 s adhered with tape to the patient's tibialis anterior. Surface electromyography was completed on the same muscle. The primary outcome of this study was to determine SPA's sensitivity and specificity in detecting OT compared with surface electromyography.

Results: Fifty-nine patients with the following diagnoses were included: OT (6), Parkinson's disease, Hereditary Spastic Paraplegia, orthostatic hypotension, essential tremor, spinal cerebellar ataxia, sensory ataxia and functional movement disorder. Smartphone accelerometry detected a 13-18 Hz tremor in 5 of 6 patients diagnosed with OT by sEMG with no false positives in other conditions, yielding a sensitivity of 83%, specificity of 100% in the cohort we studied.

Conclusions: Though a larger sample size is desirable, preliminary data suggest that smartphone accelerometry is an alternative to surface electromyography in diagnosing OT.

Keywords: Accelerometry; Movement disorders; Neurology; Orthostatic tremor; Smartphone.

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Conflict of interest statement

The authors declare that they have no current or prior potential conflicts of interest related to the research covered in the article.

Figures

Fig. 1
Fig. 1
The StudyMyTremor application display showing the numerical peak frequency based on spectrum analysis of 15.32 Hz, characteristic of OT
Fig. 2
Fig. 2
SEMG recording showing a 16 Hz tremor over a 1 s interval consistent with OT
See this image and copyright information in PMC

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