P069 The prevalence and functional relevance of ipsilateral and contralateral connections to the proximal upper limb in chronic stroke survivors

Abstract

Question After stroke proximal upper limb muscles are innervated not only by contralateral but also by ipsilateral connections. These connections can be probed by transcranial magnetic stimulation (TMS) but whether these connections contribute to the functional recovery of upper limb movements is not clear. Methods We therefore established proximal upper limb muscle active motor evoked potentials (MEPs) when delivering 20 stimulations to both the affected and unaffected hemisphere of 19 chronic stroke survivors (mean age: 59 years, SD 10.2 years, 5 female, average onset since stroke 3 years 8 months,SD 2 year 4 months) at 70% maximal TMS stimulator output (Magstim 200 squared device, figure 8 coil). In addition, we measured each individuals Fugl-Meyer upper limb score, their endpoint accuracy and movement speed when performing a reaching protocol in a robotic manipulandum and proximal muscle power. Spearman and Pearson’s correlations were performed to assess correlations of Fugl-Meyer scores and baseline endpoint accuracy respectively, with MEP measures on a subject-by-subject basis. Results When stimulating the affected hemisphere at 70%, active MEPs were evoked in the affected weak upper limb in an average of 49% of stimulations. Responses were also seen in 19% of the stimulations delivered to the unaffected hemisphere via the ipsilateral pathway. There was a clear correlation of the presence of responses when stimulating the affected hemisphere and Fugl-Meyerscore (rho = .579, p. Conclusion In summary the findings in our stroke population support previous studies showing that intact corticospinal connections from the affected hemisphere are associated with good performance and recovery. We further observe that ipsilateral responses from the unaffected hemisphere are more common after stroke but that they are not correlated to function. Whether the relevance of these connections could be altered by targeted interventions in the acute period after stroke, when neuroplasticity is increased, should be further investigated.