Ipsilesional motor area size correlates with functional recovery after stroke: a 6-month follow-up longitudinal TMS motor mapping study.

Purpose: Transcranial magnetic stimulation (TMS) and measurements of upper limb function were longitudinally applied to gain further insights into processes involved in functional recovery from the acute to the chronic stage after stroke.

Methods: 10 acute stroke patients were monitored over 6 months behaviourally and with established TMS protocols. By using neuronavigated motor mapping, behavioural parameters, and a mixed model analysis, the role of the frontal and parietal part of the motor area of both hemispheres for functional recovery was determined.

Results: Size and volume of the ipsilesional motor area (MAipsi) were significantly decreased in the acute phase compared to the contralesional motor area (MAcontra). Size of MAipsi, especially its frontal part, changed over time and was positively correlated with functional recovery, whereas resting motor threshold, volume of both MA or the shift of its center of gravity did not show any association with recovery.

Conclusion: The present data suggests the presence of a positive correlation between changes of the motor representation of the lesioned hemisphere and functional recovery after stroke. A possible interpretation is that rather (re-)activated corticomotor outputs are substrates of functional recovery after stroke than increased efficacy of residual, non-lesioned pathways.