Diagnosis of orthostatic tremor using smartphone accelerometry

Area of Science:

• Neurology
• Biomedical Engineering
• Movement Disorders

Background:

• Primary orthostatic tremor (OT) is a rare movement disorder causing a 13-18 Hz leg tremor upon standing, relieved by walking or sitting.
• Diagnosis of OT typically requires surface electromyography (sEMG) due to the tremor's low amplitude and invisibility.
• The diagnostic accuracy of smartphone accelerometry (SPA) for OT remains largely unknown.

Purpose of the Study:

• To evaluate the sensitivity and specificity of smartphone accelerometry (SPA) in diagnosing orthostatic tremor (OT).
• To compare the diagnostic performance of SPA against surface electromyography (sEMG) for OT detection.

Main Methods:

• Consecutive adults presenting with standing-induced leg shakiness or unsteadiness were enrolled.
• Tremor assessment was performed using the StudyMyTremor application on an iPhone 6s adhered to the tibialis anterior muscle.
• Surface electromyography (sEMG) was simultaneously recorded from the same muscle for comparison.

Main Results:

• Of 59 patients included, 6 were diagnosed with OT via sEMG.
• Smartphone accelerometry (SPA) detected the characteristic 13-18 Hz tremor in 5 of 6 OT patients (83% sensitivity).
• SPA demonstrated 100% specificity, with no false positives identified in patients with other neurological conditions.

Conclusions:

• Preliminary findings suggest smartphone accelerometry (SPA) is a viable alternative to surface electromyography (sEMG) for diagnosing orthostatic tremor (OT).
• While promising, further research with larger sample sizes is warranted to confirm these results.