Absence of a Transcranial Magnetic Stimulation-Induced Lower Limb Corticomotor Response Does Not Affect Walking Speed in Chronic Stroke Survivors.

Abstract

Background and Purpose- Transcranial magnetic stimulation is used to measure the functional integrity of the corticomotor system via motor evoked potentials (MEPs) in stroke. The association between corticomotor mechanisms and walking recovery is still not completely understood. This study determined the association between transcranial magnetic stimulation-induced MEPs and walking outcomes and examined the contribution of the contralesional hemisphere to walking recovery. Methods- Contralateral and ipsilateral transcranial magnetic stimulation responses from the contralesional and ipsilesional hemispheres were collected from 61 chronic stroke survivors. Clinical assessments included gait speeds, 6-minute walk distance, Timed Up and Go test, Fugl Meyer lower extremity scale, and strength measurements. Results- Stroke participants were classified based on the presence (MEP+ [n=28]) or absence (MEP- [n=33]) of MEPs in the paretic tibialis anterior and rectus femoris muscles. A between-group analyses showed no significant differences for any gait variable. MEP+ group showed significantly higher Fugl Meyer lower extremity and ankle dorsiflexor strength. Ipsilateral conductivity was not significantly different between groups. Finally, in the MEP+ group, MEP parameters did not predict gait recovery. Conclusions- Our study investigated the association between walking outcomes and neurophysiological parameters of lower limb function in a large cohort of stroke survivors. We did not find an associations between transcranial magnetic stimulation-induced tibialis anterior and rectus femoris MEPs and walking speeds. Further work is required to develop more comprehensive models in stroke for predicting walking recovery.