Neuroplasticity in constraint-induced movement therapy
Blicher JU., Near J., Næss-Schmidt E., Østergaard L., Johansen-Berg H., Stagg CJ., Nielsen JF., Ho YCL.
© Springer International Publishing Switzerland 2014. Background: In healthy subjects, decreasing GABA facilitates motor learning. Recent studies, using PET, TMS[3-5], and pharmacological challenges, have pointed indirectly to a decrease in neuronal inhibitory activity after stroke. Therefore, we hypothesize that a suppression of GABA levels post stroke might be beneficial to motor recovery during Constraint-Induced Movement Therapy (CIMT). Objective: To relate GABA changes to motor relearning after stroke through the use of j-difference edited Magnetic Resonance Spectroscopy (MRS). Methods: 21 patients (3-12 months post stroke) and 21 healthy, age-matched subjects were recruited. Patients had mild to moderate hand impairment, with at least 10° of active wrist extension, at least 10° of thumb abduction/extension, and at least 10° of extension in at least two additional digits. Patients were examined by a medical doctor and a physiotherapist prior to enrollment in the study. Patients completed two weeks of CIMT, and were scanned before and after training. For MRS a 2x2x2 cm voxel was placed on the “hand knob” (hand area located in the primary motor cortex) in the affected hemisphere of the patients and in the dominant hemisphere of the healthy subjects. GABA was expressed as a ratio to Creatine (Cr). Motor function was measured using the Wolf Motor Function Test (WMFT). Results: GABA/Cr was significantly lower (p< 0.001) in patients (0.33) at baseline compared to healthy subjects (0.42). After therapy, patients showed a significant improvement in hand function (p< 0.001), which was negatively correlated with GABA/Cr changes (R=-0.57, p=0.015) – larger improvements in patients were associated with greater reductions in GABA/Cr. Results were also significant after correcting for changes in intracortical grey matter volume. Conclusion: A decrease in GABA levels appears to facilitate motor recovery after stroke. GABA, as measured non-invasively with MRS, could be a biomarker for neuronal plasticity during post stroke recovery and guide rehabilitation interventions as transcranial direct current stimulation.