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Background and Purpose-Recovery from hemiparesis after stroke has been shown to involve reorganization in motor and premotor cortical areas. However, whether poststroke recovery also depends on changes in remote brain structures, ie, diaschisis, is as yet unresolved. To address this question, we studied regional cerebral blood flow in 7 patients (meanϮSD age, 54Ϯ8 years) after their first hemiparetic stroke. Methods-We analyzed imaging data voxel by voxel using a principal component analysis by which coherent changes in functional networks could be disclosed. Performance was assessed by a motor score and by the finger movement rate during the regional cerebral blood flow measurements. Results-The patients had recovered (PϽ0.001) from severe hemiparesis after on average 6 months and were able to perform sequential finger movements with the recovered hand. Regional cerebral blood flow at rest differentiated patients and controls (PϽ0.05) by a network that was affected by the stroke lesion. During blindfolded performance of sequential finger movements, patients were differentiated from controls (PϽ0.05) by a recovery-related network and a movement-control network. These networks were spatially incongruent, involving motor, sensory, and visual cortex of both cerebral hemispheres, the basal ganglia, thalamus, and cerebellum. The lesion-affected and recovery-related networks overlapped in the contralesional thalamus and extrastriate occipital cortex. Conclusions-Motor recovery after hemiparetic brain infarction is subserved by brain structures in locations remote from the stroke lesion. The topographic overlap of the lesion-affected and recovery-related networks suggests that diaschisis may play a critical role in stroke recovery. (Stroke. 1999;30:1844-1850.)Key Words: brain mapping Ⅲ hemiparesis Ⅲ infarction Ⅲ neuronal plasticity Ⅲ tomography, emission computed I n 1914, von Monakow 1 established the concept of diaschisis as a principle for recovery from brain lesions. Accordingly, functional changes in brain structures remote from the site of a focal brain damage, ie, diaschisis, were conceptualized as processes underlying functional recovery. The role of diaschisis, however, has remained elusive. Modern neuroimaging studies have provided first clues to the existence of diaschisis by revealing that focal brain lesions are accompanied by widespread metabolic changes involving the affected cerebral hemisphere but extending into brain areas supplied by contralateral and cerebellar arteries. 2 More recently, such remote metabolic changes have been shown to be lesionspecific in terms of cerebral topography and the related clinical deficits. 3,4 Corresponding findings in experimental models of ischemia further support the concept that these remote abnormalities are brought about acutely by neurotransmitter changes and chronically by degeneration of fiber tracts. 5 However, evidence that diaschisis is also related to recovery of function is virtually lacking.In this study we tested the hypothesis that lesion-induced, remot...

Non‐invasive mapping by focal transcranial magnetic stimulation (TMS) is frequently used to investigate cortical motor function in the intact and injured human brain. We examined how TMS‐derived maps relate to the underlying cortical anatomy and to cortical maps generated by functional imaging studies. The centres of gravity (COGs) of TMS maps of the first dorsal intersosseus muscle (FDI) were integrated into 3‐D magnetic resonance imaging (MRI) data sets in eleven subjects. In seven of these subjects the TMS‐derived COGs were compared with the COG of regional cerebral blood flow increases using positron emission tomography (PET) in an index finger flexion protocol. Mean TMS‐derived COG projections were located on the posterior lip of the precentral gyrus and TMS‐derived COG projections were in close proximity to the mean PET‐derived COG, suggesting that the two methods reflect activity of similar cortical elements. Criteria for a reliable assessment of the COG and the number of positions with a minimum amplitude of two‐thirds of the maximum motor‐evoked potential (T3Ps) were determined as a function of the number of stimuli and extension of the stimulation field. COGs and T3Ps were compared with an estimate of the size of the human motor cortex targeting α‐motoneurons of forearm muscles. This comparison suggests that TMS can retrieve spatial information on cortical organization below the macroanatomic scale of cortical regions. Finally, we studied the cortical representation of hand muscles in relation to facial and foot muscle representations and investigated hemispherical asymmetries. We did not find any evidence for a different ipsi‐ or contralateral representation of the mentalis muscle. Also, no difference was found between FDI representations on the dominant versus the non‐dominant hemisphere.