Quantification of index tapping regularity after stroke with tri-axial accelerometry

ObjectiveQuantifying intrinsic components of movement may help to better understand the nature of motor deficits after stroke. Here we quantify the ability of stroke patients to finger tap in rhythm with auditory cues given at physiological rate.MethodsUsing tri-axial accelerometry, we measured tapping regularity (Regularity Index) during auditory-cued index-to-thumb tapping at 1.25 Hz in 20 prospectively selected right-handed chronic stroke patients (mean age 61 yrs) and 20 right-handed healthy subjects (7 young and 13 age matched; mean age 24 and 58 yrs, respectively). With the aim to validate our method, two measures of clinical deficit, the European Stroke Scale (ESS) and the maximum number of index-thumb taps in 15 s (IT-Max) were recorded on the same day.ResultsThere was no effect of age or hand used on the Regularity Index in the control subjects. In patients, the Regularity Index of their affected hand was significantly worse compared to their unaffected hand and to age-matched controls (p < 0.05 and p < 0.01, respectively). The Regularity Index significantly correlated with the ESS and IT-Max in the clinically expected direction (p = 0.025 and 0.001, respectively).ConclusionThese data indicate that our method has validity to quantify finger-tapping regularity. After stroke, there is a deficit in the ability to keep pace with auditory cues that correlates, but does not equate, with other indices of motor function. Quantifying tapping regularity may provide novel insights into the mechanisms underlying recovery of finger dexterity after stroke.