What does hand motor function tell us about our aging brain in association with WMH?

Background: White matter hyperintensities (WMH) are a common cerebral finding in older people. WMH are usually asymptomatic, but excessive WMH are associated with cognitive decline and dementia. WMH are also among the neurological findings most consistently associated with declining motor performance in healthy ageing.

Aims: To determine if WMH load is associated with simple and complex motor movements in dominant and non-dominant hands in cognitively intact older subjects.

Methods: Hand motor performance was assessed with the Purdue Pegboard and Finger-tapping tests on 44 healthy right-handed participants, mean age 70.9 years (range 59-84 years). Participants also underwent magnetic resonance (MR) imaging, which were used to quantify WMH volume. The effect of WMH on the motor parameters was assessed via mediation analyses.

Results: WMH load increased significantly with age, while the motor scores decreased significantly with age. WMH load mediated only the relationship between age and left-hand pegboard scores.

Discussion: WMH mediated only the more complex Purdue Pegboard task for the non-dominant hand. This is likely because complex movements in the non-dominant hand recruit a larger cerebral network, which is more vulnerable to WMH.

Conclusions: Complex hand movements in the non-dominant hand are mediated by WMH. Subtle loss of motor movements of non-dominant hand might predict future excessive white matter atrophy.