Ipsilateral activation of the unaffected motor cortex in patients with hemiparetic stroke

Background and purpose: Recent research has shown that following stroke pat ients can display ipsilateral activity reflecting a functional link between the undamaged hemisphere and the affected upper limb on the same side of t he body. In the present study the capacity for ipsilateral activation is do cumented during recovery by using transcranial magnetic stimulation (TMS) a nd transcranial Doppler (TCD). Methods: Fourteen patients affected by hemispheric stroke were examined wit h TMS and TCD within 48 h of onset, and again 6 months later. Neurological signs were scored with reference to the NIHSS, and patients executed a thum b to finger opposition task so as to further estimate the motor deficit. Tw enty healthy volunteers represented the control population. Results: (1) Both TMS and TCD yielded homogeneous results showing ipsilater al activity between affected hands and undamaged hemispheres. On stimulatin g the motor cortex 3 cm anterior and 3 cm lateral to Ct, a scalp site remot e from the primary motor area, ipsilateral, motor evoked potentials (iMEPs) from hand muscles were found in recovered patients. (2) In 8 controls iMEP s with smaller amplitudes than patients could be obtained by stimulating on ly the left hemisphere. (3) TCD revealed increased blood flow velocity in t he ipsilateral:MCA by activating the recovering hand (10.5 +/- 3.3%; P < 0. 001). Conclusion: TM reveals a specific area in the motor cortex from which ipsil ateral MEPs can be elicited and both TMS and TCD indicate that an ipsilater al corticospinal tract can be accessible in some adult controls or becomes unmasked after cerebral damage. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.