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Introduction: Botulinum toxin is considered a first-line treatment for focal spasticity after stroke, and its peripheral effects have been well documented. We set out to demonstrate and describe any effects it may have in the central nervous system, using fMRI to record brain activation patterns before and after its administration. Materials and Methods: 17 subjects comprising 7 ischemic stroke patients affected by upper limb spastic hemiplegia, and 10 healthy controls were recruited and underwent three fMRI scans while performing a motor imagery task (finger tapping). Test subjects underwent fMRI before botulinum toxin therapy (T0), 4 weeks later (T1), and after 8 weeks (T2), and untreated control subjects were tested at 0, 4 and 8 weeks. The finger-tapping task was performed twice each session in both groups. Both test and control subjects performed only daily passive muscle stretching exercises between T0, T1, and T2 MR scans. Results: fMRI confirmed the technical feasibility of the “motor imagery” paradigm in activating the motor areas in healthy subjects. While second-level analysis of the control group showed no modification in the pattern of brain activation during the finger-tapping imagery task between T0, T1, and T2, increasing focalization of mean brain activation, accompanied by a gradual reduction in secondary motor area activation after treatment (SMA and Brodmann 6) in the test group. Conclusions: This confirms the efficacy of motor imagery as an fMRI paradigm to open a “window” into the brain that enables us to study the processes of motor function recovery after stroke in vivo. Our data show that peripheral injection of botulinum toxin alone brings about a progressive alteration in the reorganization of cortical activation after stroke, thereby confirming its therapeutic and central effects. The progressive reduction and greater focalization of activation seen continued over time, in line with the latest “small world network” theories on cortical and subcortical reorganization of cerebral functions after stroke. |
