Longitudinal Plasticity Across the Neural Axis in Acute Stroke

BACKGROUND: With the advent of novel brain stimulation techniques aimed at improving functional outcome, understanding poststroke plasticity becomes critical for the appropriate selection of patients and optimal timing to introduce neuromodulatory interventions. OBJECTIVE: To better define the temporal evolution of central and peripheral neuroplastic changes in the first 3 months after stroke and their clinical implications. METHODS: Transcranial magnetic stimulation, peripheral nerve excitability, and clinical assessments were undertaken longitudinally in 31 acute stroke patients, comprising a total of 384 clinical studies. RESULTS: During the hyperacute phase (<7 days), short-interval intracortical inhibition (SICI) was significantly reduced in lesioned (4.3% ± 1.3%) and contralesional hemispheres (3.6% ± 1.9%) compared with controls (11.4% ± 1.3%, P = .001). There were also significant alterations in accommodative properties of motor axons in the affected limb. At follow-up, SICI remained suppressed in both hemispheres in the context of significant clinical improvement. CONCLUSION: Simultaneous assessment of central and peripheral motor pathways has identified bilateral plastic changes that develop throughout the neural axis in acute stroke patients. It is proposed that these changes represent an adaptive response and that the persistent bihemispheric reduction in SICI may act to promote stroke recovery through cortical reorganization.