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Masaharu Sakoh, Leif Østergaard, Albert Gjedde, Lisbeth Røhl, Peter Vestergaard-Poulsen, Donald F. Smith, Denis Le Bihan, Saburo Sakaki and Carsten Gyldensted

Object. In this study the authors tested the hypothesis that the estimate of the apparent diffusion coefficient (ADC) of water is a reliable pathophysiological index of the viability of ischemic brain tissue.

Methods. Cerebral blood flow (CBF) and the cerebral metabolic rates of oxygen and glucose (CMRO2 and CMRglc, respectively) were measured using positron emission tomography (PET) scanning before and after permanent middle cerebral artery occlusion (MCAO) or reperfusion in pigs. The ADC value, which was measured using diffusion-weighted magnetic resonance (DW MR) imaging was compared with physiological variables obtained by PET scanning and with histological findings. After both permanent MCAO and reperfusion, the decrease in the ADC was significantly correlated with decrease in the CMRO2 and CMRglc. The infarction coincided with a CMRO2 threshold of 50% of the value measured on the contralateral side. Thus, an ADC value of 80% or 75% of the contralateral value reflected the CMRO2 threshold after permanent MCAO or reperfusion, respectively. On DW MR images, lesions with ADC values above 80% of the contralateral value are potentially reversible until 6 hours after MCAO, whereas lesions with ADC values below 75% of the contralateral value are irreversible as early as 2 hours after MCAO.

Conclusions. The ADC of water provides a reliable pathophysiological index for tailoring therapy to the condition of individual stroke patients in clinical practice.

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Stéphane Lehéricy, Hugues Duffau, Philippe Cornu, Laurent Capelle, Bernard Pidoux, Alexandre Carpentier, Stéphanie Auliac, Stèphane Clemenceau, Jean-Pierre Sichez, Ahmed Bitar, Charles-Ambroise Valery, Remy Van Effenterre, Thierry Faillot, Abbas Srour, Denis Fohanno, Jacques Philippon, Denis Le Bihan and Claude Marsault

Object. The goal of this study was to determine the somatotopical structure—function relationships of the primary motor cortex in individual patients by using functional magnetic resonance (fMR) imaging. This was done to assess whether there is a displacement of functional areas compared with anatomical landmarks in patients harboring brain tumors close to the central region, and to validate these findings with intraoperative cortical stimulation.

Methods. One hundred twenty hemispheres in 60 patients were studied by obtaining blood oxygen level—dependent fMR images in patients while they performed movements of the foot, hand, and face on both sides. There was a good correspondence between anatomical landmarks in the deep portion of the central sulcus on axial slices and the somatotopical organization of primary motor areas. Pixels activated during hand movements were centered on a small characteristic digitation; those activated during movements in the face and foot areas were located in the lower portion of the central sulcus (lateral to the hand area) and around the termination of the central sulcus, respectively. In diseased hemispheres, signal-intensity changes were still observed in the projection of the expected anatomical area. The fMR imaging data mapped intraoperative electrical stimulation in 92% of positive sites.

Conclusions. There was a high correspondence between the somatotopical anatomy and function in the central sulcus, which was similar in normal and diseased hemispheres. The fMR imaging and electrical stimulation data were highly concordant. These findings may enable the neurosurgeon to locate primary motor areas more easily during surgery.