Metabolic Changes in the Ischemic Penumbra after Carotid Endarterectomy in Stroke Patients by Localized in Vivo Proton Magnetic Resonance Spectroscopy (¹H-MRS)

Carotid endarterectomy (CEA) is known to be effective in reducing recurrent ischemic attacks, sometimes accompanied with the functional improvement, for patients with internal carotid artery (ICA) flow lesions by increase in perfusion and/or removal of embolic sources. However, the exact mechanism of how the CEA affects the cerebral metabolism in relations to the perfusion increase in noninfarcted hypoperfused peripheral areas to the center of the lesion (e.g., ischemic penumbra or border zone) is not yet clearly known. The existence of the ischemic penumbra and its long-term viability has also been argued. We designed a prospective study to investigate the metabolic changes in the ischemic penumbra for patients with ICA flow lesions and cerebral infarct (or ischemia) before and after CEA using localized in vivo proton magnetic resonance spectroscopy (¹H-MRS). The results of ¹H-MRS showed significantly decreased choline (Cho)/creatine (Cr) and increased N-acetylaspartate (NAA)/Cho ratios in the periphery of the lesion for the patients after CEA as compared to those who underwent only medical treatments. The more significant changes in the cerebral metabolite levels were observed in the patients who showed the improved cerebral perfusion by single photon emission computed tomography after CEA than in those who did not. In conclusion, our data suggest the existence of the ischemic penumbra, which were viable for a longer period than previously thought: CEA seems to improve the cerebral metabolism that may result from the improved perfusion at the ischemic penumbra.