Differential capacity of left and right hemispheric areas for compensation of poststroke aphasia

Abstract

As previous functional neuroimaging studies could not settle the controversy regarding the contribution of dominant and subdominant hemisphere to recovery from poststroke aphasia, language performance was related to H215O‐positron emission tomographic activation patterns in 23 right‐handed aphasic patients 2 and 8 weeks after stroke. In patients classified according to the site of lesion (frontal, n = 7; subcortical, n = 9; temporal, n = 7) and in 11 control subjects, flow changes caused by a word repetition task were calculated in 14 regions representing eloquent and contralateral homotopic areas. These areas were defined on coregistered magnetic resonance imaging scans and tested for significance (Bonferroni corrected t test, α = 0.0036). At baseline, differences in test performance were only found between the subcortical and temporal group. The extent of recovery, however, differed and was reflected in the activation. The subcortical and frontal groups improved substantially; they activated the right inferior frontal gyrus and the right superior temporal gyrus (STG) at baseline and regained left STG activation at follow‐up. The temporal group improved only in word comprehension; it activated the left Broca area and supplementary motor areas at baseline and the precentral gyrus bilaterally as well as the right STG at follow‐up, but could not reactivate the left STG. These differential activation patterns suggest a hierarchy within the language‐related network regarding effectiveness for improvement of aphasia; ie, right hemispheric areas contribute, if left hemispheric regions are destroyed. Efficient restoration of language is usually only achieved if left temporal areas are preserved and can be reintegrated into the functional network. Ann Neurol 1999;45:430–438

Verbal language spontaneous recovery after ischemic stroke

“…Researches show that the recovery is a complex process that depends on neuropsychological processes and environmental factors. The reorganization processes begin soon after the injury 23 . This cortical area reorganization related to language (temporal chain pre-existing frontal), consists in the activation of not injured areas in both hemispheres, but particularly the right hemisphere, that may be decisive for the recovery of the language function 11,[22][23][24][25] .…”

“…The reorganization processes begin soon after the injury 23 . This cortical area reorganization related to language (temporal chain pre-existing frontal), consists in the activation of not injured areas in both hemispheres, but particularly the right hemisphere, that may be decisive for the recovery of the language function 11,[22][23][24][25] . In this sample only 15 patients were under speech treatment, different from what happens in the United States, where most of the patients who have language disturbs achieve specific treatment to improve the maximum recovery 26 .…”

Bilateral reorganization of posterior temporal cortices in post‐lingual deafness and its relation to cochlear implant outcome

“…Unilateral cortical lesions can induce further dysfunction in the same cortical hemisphere [He et al, 2007;Price et al, 2001] or elicit a compensation by recruiting homologous areas in the contralateral hemisphere [Heiss et al, 1999;Winhuisen et al, 2005Winhuisen et al, , 2007, e.g., through disinhibition of transcallosal connections [Thiel et al, 2006;Warren et al, 2009]. As most cognitive functions are asymmetrically implemented in the brain [Formisano et al, 2008;Hickok and Poeppel, 2007;Hugdahl, 2000], the engagement of the contralateral cortex may be less efficient than the primary functional organization, and hence maladaptive [Kell et al, 2009;Marsh and Hillis, 2006;Martin and Ayala, 2004;Naeser et al, 2005;Preibisch et al, 2003;van Oers et al, 2010].…”

PET imaging in ischemic cerebrovascular disease: current status and future directions

“…In the following weeks and months, activation shifts back to the dominant hemisphere. This backward shift varies considerably and might be responsible for the successful recovery of language function [107] . For successful rehabilitation, the reactivation of networks in the dominant hemisphere seems to be a more effi cient strategy than recruiting homologous brain regions in the unaffected non-dominant hemisphere.…”