Stroke and action slowing: mechanisms, determinants and prognosis value

The present study aimed to determine the mechanisms and determinants of stroke-related action slowing.

Thirty-six stroke patients not presenting any clinical motor deficit of the preferred hand (mean post-stroke delay 11 months) were compared to matched controls on Finger Tapping test (motor speed), Visual Inspection Time test (visual perceptual speed) and Simple and Choice Reaction Time tests.

Patients were slower on all tests except Choice Reaction Time: Visual Inspection (p = 0.003), Finger Tapping test (p = 0.001), Simple Reaction Time (p = 0.002) tests were impaired including performance measured with the ipsi-lesional hand. This pattern and the uniform lengthening across the entire reaction time distribution both suggest that psychomotor slowing was due to slowing of perceptual and motor processes. The main determinant of action slowing was lesion location: (1) Visual Inspection Time = right inferior parietal lobulus (OR 18, 95% CI 2.9-108); (2) Finger Tapping = left frontal middle gyrus (OR 18, 95% CI 2.9-108) and lenticular nucleus (OR 59, 95% CI 1.9-1,775), and (3) Simple Reaction Time = right lenticular nucleus (OR 110, 95% CI 8-1,490) and posterior fossa (OR 55, 95% CI 3.4-890). Finally poor outcome depended on Tapping Frequency measured with the contra-lesional index (OR 0.1, 95% CI 0.02-0.5; p = 0.0005) and impairment on the Token test (OR 151, 95% CI 2.24-1136; p = 0.02).

This study shows that stroke-related action slowing is mainly due to slowing of perceptual and motor processes. Action slowing was related to lesions of the large network. Finally Tapping Frequency is an independent predictor of outcome. This supports that action slowing is an important consequence of stroke and that it is a promising prognosis index.