Deterioration of Hemiparesis after Recurrent Stroke in the Unaffected Hemisphere: Three Further Cases with Possible Interpretation

Abstract

Background: The concept of neural reorganization after brain damage is already well established, and many previous studies have successfully reported the translocation of the neural activation in the motor-related cortices during motor tasks using functional imaging modalities. Several primate and human studies have suggested the formation of newly reorganized tracts in the ipsilesional or contralesional hemisphere, but the mechanism for the formation of these tracts is still largely unknown. Methods: Three acute stroke patients who presented with abrupt deterioration of their right-sided hemiparesis due to the infarcts following a recurrent stroke in the originally unaffected hemisphere were studied using magnetic resonance imaging (MRI), MR angiography and single-photon emission CT. The relationship between the neurological symptom on admission and the precise location of the new infarct was carefully investigated from the perspective of reorganization. Results: Diffusion-weighted MRI showed a new subcortical infarct in the right hemisphere contralateral to the initial stroke in all patients. These new lesions involved the thalamus, globus pallidus or corona radiata, sparing the area of the internal capsule. T₂-weighed MRI on admission showed an old infarct in the left middle cerebral artery territory, which had caused the original right-sided hemiparesis. Conclusion: It is proposed that the ‘extrapyramidal’ motor pathway in the unaffected hemisphere is associated with poststroke neural reorganization.

Ipsilateral hemiparesis in ischemic stroke patients

“…The responsible lesions of ipsilateral hemiparesis were located along the corticospinal tract in all 17 of the previously reported patients . Moreover, there was no observed hemiparesis contralateral to the recent ischemic lesions in any of the present patients.…”

“…Previous strokes contralateral to the recent strokes were present in 12 of our patients and in eight of 17 reported patients (Table ) with ipsilateral hemiparesis . Moreover, these past strokes manifested unilateral motor deficits contralateral to the lesions in all of the present and previously reported patients.…”

“…Cases of ipsilateral hemiparesis or deterioration of hemiparesis ipsilateral to the cerebral injury are known; to the best of our knowledge, there are reports of 17 such patients (Table ). Ipsilateral hemiparesis is hypothesized to be caused by injury to the uncrossed corticospinal tract in patients without decussation of the corticospinal tract, injury to the uncrossed corticospinal tract acquired after prior brain injury, injury to the ipsilateral extrapyramidal motor pathway or premotor cortex, or transhemispheric diaschisis from the affected side …”

Post-stroke remodeling processes in animal models and humans

“…Another detour was demonstrated in a study on ventral PMC neurons of monkeys that formed connections with perilesional M1 neurons. 71 The axonal detour has also been observed in rat models 11 and in patients 72 at the cerebral (transcallosal fibers, red nucleus), pons, and spinal level and may correspond to a “double-crossing” with the take-over of motor functions by the contralesional hemisphere.…”

Reorganization of cerebral networks after stroke: new insights from neuroimaging with connectivity approaches

“…This might explain the clinical observation that a second stroke sometimes re-instates recovered symptoms from a first stroke, even if the opposite (previously ‘healthy’) hemisphere is affected (Yamamoto et al , 2007). …”