The relationship between motor deficit and primary motor cortex hemispheric activation balance after stroke: longitudinal fMRI study

Cinzia Calautti (1) , P Simon Jones (1) , Marcello Naccarato (1) , Nick Sharma (1) , Diana Day (1) , Ed Bullmore (2) , Elizabeth Warburton (3) , Jean-Claude Baron (4)

1 University of Cambridge, Dept of Clinical Neurosciences
2 University of Cambridge, Wolfson Brain Imaging Centre
3 Addenbrooke's Hospital
4 Department of Clinical Neurosciences [Cambridge]

Background: In the chronic stage of stroke, previous work has shown that the worse the hand motor deficit the greater the shift of primary motor cortex (M1) activation towards the contralesional hemisphere (i.e., unphysiological). Whether the same relationship applies at an earlier stage of recovery in serially studied patients is not known. Methods: fMRI of fixed-rate auditory-cued affected index finger tapping was obtained at 2 time points (mean 36 and 147 days post stroke) in a cohort of 9 ischaemic stroke patients (age: 56±9 yrs; 3 women/6 men; 7 subcortical, 1 medullary and 1 cortical). On each fMRI day the unaffected/affected ratio of maximal index tapping rate (IT-R) was obtained. To assess the M1 hemispheric activation balance, we computed the classic Laterality Index (LI). The correlation between LI and IT-R was computed for each time point separately. Results: The expected correlation between LI-M1 and IT-R, i.e. motor performance worse with more unphysiological LI, prevailed at both time points (Kendall p= 0.008 and 0.058, respectively), with no statistically significant difference between the two regressions. The same analysis for the dorsal premotor cortex and the supplementary motor area showed no significant correlation at either time-point. Conclusion: These results from a small cohort of longitudinally-assessed patients suggest that the relationship between M1 laterality index and hand motor performance appears independent of time since onset of stroke. This in turn may suggest that attempting to restore the hemispheric balance by enhancing ipsilesional M1 and/or constraining contralesional M1 activity may have consistent efficacy throughout recovery.

Mots clés: FUNCTIONAL IMAGING; MRI; STROKE

Cinzia Calautti, P Simon Jones, Marcello Naccarato, Nick Sharma, Diana Day, et al.. The relationship between motor deficit and primary motor cortex hemispheric activation balance after stroke: longitudinal fMRI study. Journal of Neurology, Neurosurgery and Psychiatry, 2010, 81 (7), pp.788. ⟨10.1136/jnnp.2009.190512⟩. ⟨hal-00557415⟩